Chapter XIX: Letter XLIX

_GEOGRAPHICAL DISTRIBUTION OF INSECTS;
THEIR STATIONS AND HAUNTS;
SEASONS; TIMES OF ACTION AND REPOSE._

Though no subject is more worthy of the attention of the Entomologist than the _Geographical Distribution_ of insects, yet perhaps there is none connected with the science, for the elucidation of which he is furnished with fewer materials. The geographer of these animals sitting by his fireside, even supposing his museum as amply stored as that of Mr. MacLeay, and the _habitats_ of its contents as accurately indicated, still labours under difficulties that are almost insuperable; so that it is next to impossible, with our present knowledge of the subject, to give _satisfactory_ information upon _every_ point which it includes. Had he the talents and opportunities of a Humboldt, and could, like him, traverse a large portion of the globe, he would endeavour to note the elevation, the soil and aspect, the latitude and longitude, the mean temperature and meteorological phænomena, the season of the year, the kind of country, and other localities connected with the insects he captured, and so might build his superstructure upon a sure basis. But these are things seldom registered by travellers that take the trouble to collect insects; who, if they specify generally the country in which any individual was found, think they have done enough. But to say that an insect was taken in India, China, New Holland, and North or South America,--when we consider the vast extent of those regions,--is saying little of what one wishes to know even with respect to its _habitat_. You must regard therefore, after all, what I have been able to collect,--and for which I am greatly indebted to the labours of my few but able precursors in this walk,--as merely approximations to an _outline_, rather than as a correct _map_ of insect Geography.

Amongst the numerous obligations that he conferred upon Natural History, Linné was the first Naturalist who turned his attention to the _Geographical Distribution_ of its objects, especially that of the _Vegetable_ Kingdom[1458]: and the accomplished traveller Baron Humboldt, by the observations he made on this subject in the course of his peregrinations in tropical America, has furnished the Botanist with a clue which, duly followed, will enable him to perfect that part of his science; an end to which the learned observations of Messrs. R. Brown and Decandolle have greatly contributed[1459]. With regard to _animals_, Mr. White, so long ago as 1773, had observed that they, as well as plants, might with propriety be arranged geographically[1460]: and in 1778 Fabricius in his _Philosophia Entomologica_ applied the principle to _insects_[1461]. Nearly forty years elapsed before any improvement or enlargement of this last department was attempted; when in 1815 M. Latreille, stimulated by what had been effected in Botany, in a learned and admirable memoir[1462] endeavoured to place Entomology in this respect by the side of her more fortunate sister: and subsequently Mr. W. S. MacLeay, in the memorable work so often quoted in our correspondence, has viewed the subject in another light, and added some important information to what had been before collected[1463].

The point now under consideration naturally divides itself into two principal branches;--the _numerical_ distribution of insects, and the _topographical_.

I. By the _numerical_ distribution of insects I mean not only the number which PROVIDENCE has employed to carry on its great plan on this terraqueous globe, or any given portion of it; or of the species of which each group or genus may be supposed to consist; or of the comparative number of individuals furnished by each species,--points of no easy solution: but more particularly their distribution according to their _functions_, whether they prey upon _animal_ or _vegetable_ matter, and in its _living_ or _decaying_ state.

We have no data enabling us to ascertain with any degree of accuracy the actual _number_ of species of insects and _Arachnida_ distributed over the surface of the globe; but it is doubtless regulated in a great degree by that of plants. We should first then endeavour to gain some just though general notion on that head. Now Decandolle conjectures that the number of the species of plants, 60,000 being already known, may be somewhere between 110,000 and 120,000[1464]. If we consider with reference to this calculation, that though the great body of the mosses, lichens, and sea-weeds are exempt from the attack of insects, yet as a vast number of phanerogamous plants and fungi are inhabited by _several_ species, we may form some idea how immense must be the number of existing insects; and how beggarly does Ray's conjecture of 20,000 species[1465], which in his time was reckoned a magnificent idea, appear in comparison! Perhaps we may obtain some approximation by comparing the number of the species of insects already discovered in _Britain_ with that of its _phanerogamous_ plants. The latter,--and it is not to be expected that any large number of species have escaped the researches of our numerous Botanists,--may be stated in round numbers at 1500, while the British insects, (and _thousands_ it is probable remain still undiscovered,) amount to 10,000; which is more than _six_ insects to _one_ plant. Now though this proportion, it is probable, does not hold universally; yet if it be considered how much more prolific in species tropical regions are than our chilly climate, it may perhaps be regarded as not very wide of a fair medium. If then we reckon the phanerogamous vegetables of the globe in round numbers at 100,000 species, the number of insects would amount to 600,000. If we say 400,000, we shall perhaps not be very wide of the truth. When we reflect how much greater attention has been paid to the collection of plants than to that of insects, and that 100,000 species of the latter may be supposed already to have a place in our cabinets[1466], we may very reasonably infer that at least _three fourths_ of the existing species remain undiscovered.

Certain groups and genera are found to contain many more species than others: for instance, the _Coleoptera_ and _Lepidoptera_ Orders than the _Orthoptera_ and _Neuroptera_; the _Rhincophora_ than the _Xylophagi_: the _Dytiscidæ_ than the _Gyrinidæ_; _Aphodius_ than _Geotrupes_; _Carabus_ than _Calosoma_. Again, some insects are much more prolific than others. Thus the _Diptera_ Order, though not half so numerous with respect to _species_ as the _Coleoptera_, exceeds it greatly in the number of _individuals_, filling the air in every place and almost at every season with its dancing myriads. We rarely meet with a single individual of the most common species of _Calosoma_ or _Buprestis_; whilst the formicary, the termitary, the vespiary, and the bee-hive send forth their thousands and tens of thousands; and whole countries are covered and devastated by the _Aphides_ and the Locusts. An all-wise PROVIDENCE has proportioned the numbers of each group and species to the work assigned to them. And this is the view in which the numerical distribution of insects is most interesting and important: and we are indebted to Mr. W. S. MacLeay for calling the attention of Entomologists more particularly to this part of our present subject.

With regard to their _functions_, insects may be primarily divided into those that feed upon _animal_ matter and those that feed upon _vegetable_. At first you would be inclined to suppose that the _latter_ must greatly exceed the _former_ in number: but when you reflect that not only a very large proportion of Vertebrate animals, and even some _Mollusca_[1467], have more than _one_ species that preys upon them, but that probably the majority of insects, particularly the almost innumerable species of _Lepidoptera_, are infested by parasites of their own class, sometimes having a different one appropriated to them in each of their preparatory states[1468], and moreover that a large number of beetles and other insects devour both living and dead animals,--you will begin to suspect that these two tribes may be more near a counterpoise than at first seemed probable. In fact, out of a list of more than 8000 British insects and _Arachnida_ taken several years ago, and furnished chiefly by Mr. Stephens, I found that 3894 might be called carnivorous, and 3724 phytiphagous[1469]; so that, speaking roundly, they might be denominated equiponderant.

Carnivorous and phytiphagous insects may be further subdivided according to the _state_ in which they take their _food_,--whether they attack it while _living_, or not till after it is _dead_. To adopt Mr. W. S. MacLeay's phraseology, the former may be denominated _thalerophagous_, and the latter _saprophagous_. The British saprophagous _carnivorous_ insects, compared with those that are thalerophagous, are about as 1:6; while the phytiphagous ones are as 1:9. The _thalerophaga_ in both tribes may be further subdivided as they take their food by _suction_ or _mastication_: in the _carnivorous_ ones, the suckers to the masticators in Britain are nearly as 1:6; but with respect to the _phytiphagous_ tribe you must take into consideration that some insects imbibing their food by _suction_ in their _perfect_ state (as the great body of the _Lepidoptera_), _masticate_ it when they are _larvæ_: deducting therefore from both sides the insects thus circumstanced, the masticators will form about _three fourths_ of the remaining British thalerophagous insects. Another circumstance belonging to this head must not be passed without notice:--there are certain insects feeding upon liquid food that do not _suck_, but _lap_ it. This is the case with the _Hymenoptera_, who, though they are mandibulate, generally lap their food (the nectar of flowers) with their tongue, and may be called _lambent_ insects: nor is this practice confined to that order, but all the mandibulate insects that feed on that substance merit the same appellation. The absorption of this nectar is so important a point in the economy of nature, that a very large proportion of the insect population of the globe in their perfect state, are devoted to it. Considerably more than half the species indigenous to Britain fulfill this function, and probably in tropical countries the proportion may be still larger.

To push this analysis still further--Amongst our carnivorous thalerophaga, _aphidivorous_ insects are about as 1:14; and amongst the phytiphagous, the _fungivorous_ ones form about a _twentieth_; and the _granivorous_ about a _twenty-fifth_ part of the whole. Again: in the _saprophaga_ the _lignivorous_ tribes form more than _half_, and the _coprophagous_ ones more than a _third_.

If you wish to know further the relative proportions of the different _Orders_ to each other--The _Coleoptera_ may be stated as forming at least 1:2 of our intire insect population; the _Orthoptera_ and _Dermaptera_ as about 1:160; the _Hemiptera_ as 1:15; the _Lepidoptera_ as more than 1:4; the _Neuroptera_ with the _Trichoptera_ as 1:29; the _Hymenoptera_ as about 1:4; the _Diptera_ as not 1:7; and the _Aptera_ and _Arachnida_ as perhaps amounting to 1:19[1470].

To extend this inquiry to _exotic_ and more particularly to _extra-European_ insects, in the present state of our knowledge, would lead to no very satisfactory results. The lists we have are so imperfect, that those which tell most in this country,--I mean the more minute insects and the _Brachyptera_--have hitherto formed a very small, if any part, of the collections made _out_ of Europe. Mr. W. S. MacLeay however, who, besides his father's (particularly rich in _Petalocera_), has had an opportunity of examining the Parisian and other cabinets, finds that the species of _coprophagous_ insects _within_ the tropics, to those _without_, are nearly in the proportion of 4:3; and that the coprophagous _Petalocera_, to the remainder of the saprophagous ones, may be represented by 3:2[1471]. It may be inferred, from the superabundance of plants and animals in equinoctial countries, that the number of species of insects in general is greater within than without the tropics: the additional momentum produced by the vast size of many of the tropical species must also be taken into consideration.

II. There are three principal points that call for attention under the _second_ branch of our present subject--the _topographical_ distribution of insects; namely, their _Climates_, their _Range_, and their _Representation_.

i. Entomologists, taking _heat_ for the principal regulator of the station of insects, have divided the globe into entomological _climates_. Fabricius considers it as divisible into _eight_ such climates, which he denominates the _Indian_, _Egyptian_, _Southern_, _Mediterranean_, _Northern_, _Oriental_, _Occidental_, and _Alpine_. The first containing the tropics; the second, the northern region immediately adjacent; the third, the southern; the fourth, the countries bordering on the Mediterranean sea, including also _Armenia_ and _Media_; the fifth, the northern part of Europe interjacent between Lapland and Paris; the sixth, the northern parts of Asia where the cold in winter is intense; the seventh, North America, Japan, and China; and the eighth, all those mountains whose summits are covered with eternal snow[1472]. M. Latreille objects to this division, as too vague and arbitrary and not sufficiently correct as to temperature; and observes, with great truth, that as places where the temperature is the same, have different animals, it is impossible, in the actual state of our knowledge, to fix these distinctions of climates upon a solid basis. The different elevations of the soil above the level of the sea, its mineralogical composition, the varying quantity of its waters, the modifications which the mountains, by their extent, their height, and their direction, produce upon its temperature; the forests, larger or smaller, with which it may be covered; the effects of neighbouring climates upon it,--are all elements that render calculations on this subject very complicated, and throw a great degree of uncertainty over them[1473]. This learned Entomologist would judiciously consider entomological climates under another view,--that which the genera of _Arachnida_ and insects _exclusively_ appropriated to determinate spots or regions would supply[1474]. Linné's _dictum_ with regard to genera will here also apply; "Let the insects point out the climate, and not the climate the insects." If you expect invariably to find the same insects within the same parallels of latitude, you will be sadly disappointed; for, as our author further observes, "The totality or a very large number of _Arachnida_ and insects, the temperature and soil of whose country are the same, but widely separated, is in general, even if the countries are in the same parallel, composed of different species[1475]." The natural limits of a country,--as mountainous ranges, rivers, vast deserts, &c.,--often also say to its insect population, "No further shall ye come;" interposing a barrier that it never passes[1476]. Humboldt observes, with respect to the _Simulia_ and _Culices_ of South America, that their geographical distribution does not appear to depend solely on the _heat_ of the climate, the excess of humidity, or the thickness of forests; but on local circumstances that are difficult to characterize[1477]: and Mr. W. S. MacLeay makes a similar observation upon that of _Gymnopleurus_[1478]. So that the real insect climates, or those in which certain groups or species appear, may be regarded as fixed by the will of the CREATOR, rather than as certainly regulated by any _isothermal_ lines. Still, however, under certain limitations, it must be admitted that the temperature has much to do with the station of insects. The increase of caloric is always attended with a proportional increase in the number and kind of the groups and species of these beings. If we begin within the polar regions of ice and snow, the list is very meager. As we descend towards the line, their numbers keep gradually increasing, till they absolutely _swarm_ within the tropics. Something like this takes place in miniature upon _mountains_. Tournefort long since observed at the summit of Mount Ararat the plants of Lapland; a little lower, those of Sweden; next, as he descended, those of Germany, France, and Italy; and at the foot of the mountain, such as were natural to the soil of Armenia. And the same has been observed of insects. Those that inhabit the _plains_ of _northern_ regions have been found on the _mountains_ of more _southern_ ones; as the beautiful and common Swedish butterfly _Parnassius Apollo_, on the mountains of France, and _Prionus depsarius_ on those of Switzerland[1479].

M. Latreille, having given a rapid survey of the peculiar insect-productions of different countries, next attempts a division of the globe into _climates_, which he thinks may be made to agree with the present state of our knowledge, and be even applicable to future discoveries. He proposes dividing it primarily into _Arctic_ and _Antarctic_ climates, according as they are situated _above_ or _below_ the equinoctial line; and taking twelve degrees of latitude for each climate, he subdivides the whole into _twelve_ climates. Beginning at 84° N. L. he has _seven Arctic_ ones, which he names _polar_, _subpolar_, _superior_, _intermediate_, _supratropical_, _tropical_, and _equatorial_: but his _antarctic_ climates, as no land has been discovered below 60° S. L., amount only to _five_, beginning with the _equatorial_ and terminating with the _superior_. He proposes further to divide his climates into _subclimates_, by means of certain _meridian lines_; separating thus the _old_ world from the _new_, and subdividing the _former_ into two great portions,--an _eastern_, beginning with _India_, and a _western_, terminating with _Persia_. He proposes further that each climate should be considered as having 24° of longitude, as well as 12° of latitude[1480]. In this chart of insect Geography he states that he has endeavoured to make his climates agree with the actual distribution of insects[1481]; and it should seem that in many cases such an agreement actually does take place: yet the division of the globe into climates by _equivalent_ parallels and meridians, wears the appearance of an artificial and arbitrary system, rather than of one according with nature.

He has also pointed out another index to insect climates, borrowed from the _Flora_ of a country. Southern forms in Entomology, he observes, _commence_ where the _vine_ begins to prosper by the sole influence of the mean temperature; that they are _dominant_ where the _olive_ is cultivated; that species still _more_ southern are compatriots of the _orange_ and _palmetto_; and that some _equatorial_ genera accompany the _date_, the _sugar-cane_, the _indigo_ and _banana_[1482]. The idea is very ingenious, and, under certain limitations, supplies a useful and certain criterion. For though none of these plants are _universal_ in isothermal parallels of latitude; yet, as plants are more conspicuous than insects, the Entomologist, furnished with an index of this kind, may by it be directed in his researches for them; and in all countries in which there is a material change of the climate, as in France, there will be a proportional change in the _vegetable_ accompanied by one in the _insect_ productions.

ii. In considering the _range_ of insects I shall first advert to that of _individual_ species. At the extreme limits of phanerogamous vegetation we find a species of humble-bee (_Bombus arcticus_), which, though it is not known to leave the Arctic circle, has a very extensive range to the _westward_ of the meridian of Greenwich, having been traced from Greenland to Melville Island; while to the _eastward_ of that meridian it has not been met with. In Lapland its place appears to be occupied by _B. alpinus_ and _lapponicus_, with the former of which, though quite distinct, it was confounded by O. Fabricius; but whether these range further _eastward_ of that meridian has not been ascertained. From its being found in the Lapland _Alps_[1483], it may be conjectured that _B. alpinus_ ranges as high on this side as _B. arcticus_ on the other, and may perhaps be found in _Nova Zembla_. Some species that have been taken in Arctic regions are not confined to them. Of this kind is _Dytiscus marginalis_, which appears common in Greenland, abundant in Britain, and is dispersed over all Europe; while _D. latissimus_ is more confined, neither ranging so far to the north or south; and though found in Germany, not yet discovered in Britain. Other species have a still more extensive range, and are common to the old world and the new. Thus _Dermestes murinus_, _Brachinus crepitans_, _Tetyra scarabæoides_[1484], _Pentatoma juniperina_, _Cercopis spumaria_, _Vanessa Antiopa_, _Polyommatus Argiolus_, _Hesperia Comma_, _Vespa vulgaris_, _Ophion luteus_, _Helophilus pendulus_, _Oscinis Germinationis_, and many besides, though sometimes varying slightly[1485], inhabit both Britain and Canada: and though vast continents and oceans intervene between us, New Holland, and Japan; yet all have some insect productions in common. With the former we possess the painted-lady butterfly (_Cinthia Cardui_), with scarcely a varying streak: and Thunberg, in his list of Japan insects, has mentioned more than _forty_ species that are found also in this country. Whether any species has a _universal_ range may be doubted, unless indeed the flea and the louse may be excepted. On the other hand, some are confined within very narrow limits. _Apion Ulicis_ for instance, abundant upon _Ulex europæus_ in Britain, has not, I believe, been found upon that plant on the continent.

The geographical distribution of _groups_, is, however, far more interesting than that of _individual species_: for in considering this we see more evidently how certain _functions_ are devolved upon certain _forms_, and can scan the great plan of PROVIDENCE, in the creation of insects, more satisfactorily than by confining our attention to the latter. Groups, according to their range, may be denominated either _predominant_, _dominant_, _sub-dominant_, or _quiescent_.

1. M. Latreille has observed, that where the empire of _Flora_ ceases, there also terminates that of Zoology[1486]. _Phytiphagous_ animals can only exist where there are _plants_; and those that are _carnivorous_ and feed upon the _former_, must of necessity stop where they stop. Even the _gnat_, which extends its northern reign so high[1487], must cease at this limit; while, where vegetation is the richest and most abundant, there the animal productions, especially the insect, must be equally abundant. I call that, therefore, a _predominant_ group, members of which are found in all the countries between these points, or from the limits of animal-depasturing vegetation in the polar regions to the line.

Generally speaking, the _carnivorous_ insects, whether thalerophagous or saprophagous, are of this description. _Calosoma_, which devours Lepidopterous larvæ, though poor in species and individuals, is widely scattered. Captain Frankland found _C. calidum_ in his Arctic journey; _C. laterale_ and _curvipes_ inhabit tropical America[1488]: _C. Chinense_, as its name indicates, is Chinese[1489]; Mr. MacLeay has an undescribed species from New Holland; and _C. retusum_ was taken in Terra del Fuego. Another genus, equally universal and richer in numbers, is the lady-bird (_Coccinella_), which keeps within due limits the _Aphides_ of every climate from pole to pole. The _Libellulina_ pursue their prey both in Greenland and New Holland. The _saprophagous_ carnivora are also similarly predominant;--the _Silphidæ_, the _Dermestidæ_, the _Brachyptera_, the _Muscidæ_, prey on carcases wherever the action of the solar beam causes them to become putrid. Many of the above insects have probably their _capital_ station, or that where the species are most numerous, in or near the tropics; but the metropolis of the _Brachyptera_, at least as far as we can judge from our present catalogues, is within the temperate zone, particularly in Britain[1490]. The coprophagous _Petalocera_ are most abundant in the hottest climates; but the _Aphodiadæ_ form a predominant group: Professor Hooker took one species in Iceland[1491], and it probably ascends higher; others are found in India and China: but the metropolis of the group is within the temperate zone. Perhaps no genus is more completely universal than _Bombus_ (_Bremus_ Jur.), which, although its centre or _metropolis_ is likewise in the northern temperate zone, extends from Melville Island to the line. It is remarkable that some of the tropical _Bombi_ wear the external aspect of _Xylocopæ_, the kindred genus most prevalent in warm climates; and, _vice versâ_, some _Xylocopæ_ resemble _Bombi_. I have a Brazilian undescribed species of the latter genus, whose black body and violet-coloured wings would almost cause it to be mistaken for a variety of _X. violacea_; and _B. antiguensis_ and _caffrus_ F., (though their aspect belies it,) which misled Fabricius, are true _Xylocopæ_. I shall mention only one other predominant group, but that one of no common celebrity, formed of the gnats, or genus _Culex_. These piping pests, with their quiver--"venenatis gravida sagittis"--annoy man almost from the pole to the line. What remarkably distinguishes them, (as was formerly observed[1492],) and also the _Simulium_ or true mosquito,--they appear to prevail most in the coldest and the hottest climates, and the Laplander and the tropical American are equally their prey; while the inhabitants of the temperate zone, with some exceptions, suffer but little from them: so that they may be stated to have both an _arctic_ and a _tropical_ metropolis.

2. There are other groups which, though their empire extends to the tropics, fall short of the polar circles:--these I call _dominant_ groups. Of this description are some of the _Scarabæidæ_. _Onthophagus_ is found both in the old world and in the new, and in the temperate and torrid zones. Its principal seat appears to be within the tropics, but it may almost be said to have also a northern metropolis. More than one species have been taken in New Holland. In general, tropical insects exceed those of colder climates in _size_; but in the genus we are speaking of, the _European_ species are usually larger than the _Indian_. _Copris_ seems more abhorrent of cold than its near relation _Onthophagus_. _C. lunaris_, which ranges northward as far as Sweden, is the only recorded species found in Europe out of Spain. Latreille says, that all the large species of this genus are equinoctial: but _C. Tmolus_, described and figured by Fischer[1493], found in Asia near Orenburg, north of 50° N. L., is as big as _C. Gigas_ or _bucephalus_. Another dominant group of _Petalocera_, remarkable for the bulk and arms of its tropical species, are the mighty _Dynastidæ_, the giants and princes of the insect race. Though their metropolis is strictly tropical, yet the scouts of their host have wandered even as far as the south of Sweden, where one of them, _Oryctes nasicornis_, is extremely common. _O. Grypus_[1494] and some other species are found in South Europe; but though in a torpid state they can endure unhurt the severity of a Scandinavian winter, they cannot when revived stand the cold that often pinches Britons in the midst of summer, and therefore are unknown in our islands[1495]. The _Sphæridiadæ_, whose metropolis is within the northern temperate zone, extend from thence beyond the line, since Dr. Horsfield found two species in Java[1496]. It is probable, indeed, that this group is predominant. Some dominant groups begin at a lower latitude. Of this description are the carpenter-bees (_Xylocopa_), whose larvæ are preyed upon by that of the _Horiadæ_[1497] under _two_ forms, which extend from the tropics to about 50° N. L. Others are not common to both worlds. Thus, while _Cantharis_ is the gift of PROVIDENCE to America as well as the old world, _Mylabris_ is confined to the _latter_, where its range is very extensive;--in Europe, from South Russia to Italy and Spain; in Asia, from Siberia to India; and in Africa, from the shores of the Mediterranean to the Cape of Good Hope; which last continent, to judge from our present lists, especially the vicinity of the Cape, may be called the metropolis of the group[1498]. On the other hand, the _Rutelidæ_ and _Chlamys_, which have a range from Canada to the tropics, (within which is their metropolis,) are purely _American_ groups. Many more might be named under this head, but these will suffice for examples.

3. I call those _subdominant_ groups, which either never enter the tropics, or those tropical ones whose range does not exceed 50° of N. L. in the old world, or 43° in the new. I make this difference because, as M. Latreille observes, the southern insects which in Europe begin between 48° and 49° N. L., in America do not reach 43°.[1499] But though the winters in Canada, within the same parallel as France, are longer and more severe than those even of Great Britain or of Germany, yet the summers are intensely hot; so that though tropical _species_ do not range so high, those of a tropical _structure_, as Mr. W. S. MacLeay has intimated[1500], may be found at a higher latitude in the new world than in Europe.

The genus _Melöe_ affords an instance of a subdominant group of the first description. It ranges from Sweden to Spain and the shores of the Mediterranean, and seems a tribe almost confined to Europe, where it is not very unequally distributed. Of registered species Britain possesses the largest proportion; but Mr. W. S. MacLeay is of opinion that Spain is its true metropolis[1501]. I have a species of this genus, taken in North America by Professor Peck. The splendid genus _Carabus_ ranges still further north than _Melöe_[1502]. A very fine species (_C. cribellatus_) inhabits the polar regions of Siberia[1503]; but the metropolis of the group appears to be the temperate zone: some, however, have been found in northern Africa; and Sir Joseph Banks captured one in Terra del Fuego. Of those whose range is between the tropics and 50° N. L. we may begin with _Cicada_. One species, indeed, has been found by Mr. Bydder and others, a little higher, near the New Forest, Hampshire. We may take _Scolia_ for an example of a subdominant group beginning more southward. Its species first appear about 43° N. L., and abound in warm climates. In general most of those insects which M. Latreille denominates _meridional_,--such as _Scarabæus_, _Onitis_, _Brentus_, _Scarites_, _Mantis_, _Fulgora_, _Termes_, _Scorpio_, &c.--come under the present head, and in fact all tropical forms that wander to any distance within the above limits from their metropolis.

4. By _quiescent_ groups I mean those that have none, or no _high_ range as to latitude, from their centre or metropolis. I say as to _latitude_, because these groups have often an extensive one as to _longitude_. Thus, Mr. W. S. MacLeay has remarked to me, that _Goliathus_ appears to belt the globe, but not under _one_ form. The types of the genus are the vast African Goliaths (_G. giganteus_, &c.), which, as well as _G. Polyphemus_, and another brought from Java by Dr. Horsfield, have, like _Cetonia_[1504], the scapulars interposed between the posterior angles of the prothorax and the shoulders of the elytra[1505]: while the South American species (_G. micans_, &c.) have not this projection of the scapulars; in this resembling _Trichius_. Mr. MacLeay further observes, that the female of the Javanese _Goliathus_ is exactly a _Cetonia_, while that of the Brazilian is a _Trichius_. But quiescent groups have not generally this ample longitudinal range. Thus, _Euglossa_, in both its types,--one represented by _Eu. cordata_, and the other by _Eu. surinamensis_,--is confined to the tropical regions of America. _Doryphora_, likewise American, seems equally confined. _Asida_, though a _southern_ genus, is not found to enter the _tropics_; and _Manticora_ and _Pneumora_ are in nearly the same predicament.

Under the present head we may consider what may perhaps be denominated without much impropriety _endemial_ groups; by which I mean those groups that are regulated, as to their limits, not so much by the temperature, or the northing and southing of the latitude, as by the general aspect and circumstances of the country. Thus, the vast and nearly insular continent of _Africa_, almost as wide as it is long, and situated in or near the tropics, instead of inland seas or sea-like rivers, is intersected by parched sandy deserts, extending far and wide; circumstances which, though in the vicinity of its streams it is humid, impart an unusual degree of _aridity_ as well as heat to its general atmosphere; so that it well merits the poet's epithet, _Leonum arida nutrix_; and is also peculiarly fitted for all such animals, especially insects, as delight in a dry, sandy, hot country, particularly such as are predaceous in their habits. _America_, on the other hand, exhibits quite an opposite character. It is long, and comparatively narrow; surrounded, and almost divided into two continents, by immense circumfluent oceans; watered every where by rivers and lakes that emulate seas: in some parts covered by interminable forests; in others, intersected by ridges of the loftiest mountains. These circumstances, except in its Llanos, Pampas, or table-land, give a general character of humidity to its atmosphere, and fit it particularly for the production of a vast variety of peculiar plants, and for the residence of numerous and peculiar phytiphagous insects and other animals[1506]. Midway between these two continents lies a third (for so the vast island of New Holland may be denominated), which presents new features in its general aspect, and consequently new forms both in its _Flora_ and _Fauna_, mixed with many old ones parallel to those both of the new world and the old. Perhaps Europe and Asia, with several that are peculiar, agree more in their animal productions than the continents just described.

Let us next particularize a few of the peculiar types that distinguish particular continents and countries. The genera _Manticora_, _Graphipterus_, _Glaphyrus_, _Eurychora_, _Pneumora_, _Masaris_, and many others, are peculiar to Africa. In Asia alone we find _Mimela_[1507], _Euchlora_[1508], _Colliuris_, _Catascopus_[1509], _Apogonia_[1510], a peculiar type of _Horia_, &c. In America, _Agra_, _Galerita_, _Nilio_, another type of _Horia_, _Tetraonyx_, _Rutela_, _Doryphora_, _Alurnus_, _Erotylus_, _Scotinus_[1511], _Cupes_, _Corydalis_, _Labidus_, _Heliconius_, _Castnia_, &c. And in New Holland, _Helluo_, _Elephastomus_, _Anoplognathus_, _Diphucephala_[1512], _Cerapterus_, _Heleus_, _Adelium_, _Notoclea_, _Achilus_, _Thynnus_, _Nycterobius_, &c.

The countries bordering upon the Mediterranean, the Black, and the Caspian seas, agree in producing similar insects. These countries, and the Cape of Good Hope though so distant from them, appear to be the principal seat of Heteromerous _Coleoptera_, of the genera _Lixus_ and _Brachycerus_, and of the conical _Buprestes_[1513]. But the insects of Guiana, on one side the Cordilleras, differ from those of New Granada and Peru on the other; and similar differences are observed in other _neighbouring_ countries separated by natural boundaries.

iii. Another head connected with the topographical distribution of insects relates to their _representation_ of each other. Here we may observe, that some insects represent each other only in their _form_; others also in their _function_; and others in _both_. I shall give some instances of each. In Brazil there is a group of petalocerous beetles (_Chasmodia_), one of the _Rutelidæ_, which in New Holland has a representative, as to _form_, in one of the _Cetoniadæ_ (_Schizorhina_[1514]), which, having soft mandibles, must have a different function:--it is to be observed, however, that these insects appear to approach each other in the series of affinities. Again, the _Carabidæ_ may in the same country be said to have a representative in the remarkable heteromerous genus _Adelium_[1515], which is altogether an analogy. Others are representative only in their _function_. The general function of insects is to remove _nuisances_ and to check _redundances_,--the saprophagous tribes do the one, and the thalerophagous the other. In going from the poles to the line,--in proportion as the heat increases, the quantum of work of both kinds increases; and new forms are either added to the old ones, so as to increase their momentum; or new ones, more powerfully talented, replace the old ones, and act in their stead: thus we see a gradual and interesting change take place in proportion as we approach the maximum of heat and of insect population. At the Cape, the _universal Cicindelæ_ are aided by _Manticora_; in North America, the _Silphidæ_ by a new group, the type of which is _Silpha Americana_ (_Necrophila_, K.MS.); in South America, _Copris_ by _Phanæus_. Again: _Colliuris_ and _Drypta_ of the _old_ world, in the _new_ give place to _Ctenostoma_ and _Agra_. The honey and wax of Europe, Asia, and Africa, is prepared by _bees_ congenerous with our common hive-bee (_Apis_); while in America this genus is not found as a native, but is replaced by _Melipona_ and _Trigona_[1516]; and in New Holland by a still different but undescribed type. The _Melolonthidæ_ and _Rutelidæ_ of the old and new world appear to have their work done in that country by the brilliant and numerous _Anoplognathidæ_. The _Rhipicera_ of Brazil is of a different type from that of New Holland. The singular genus _Cremastocheilus_ of North America has its representative in Africa in _Genuchus_[1517]. The _Lucani_ of the rest of the world give place in New Holland to _Lamprima_ and _Ryssonotus_.--I could produce a much greater number of examples, but these are sufficient to explain my meaning.

* * * * *

Having thus given you some, though an imperfect account, of the _geographical_ distribution of insects, I am next to say something concerning their _local_ distribution in any district, or their favourite _haunts_; a knowledge of which, with respect to those of our own country, is indispensable to the collector.

The surface of a country consists either of mountains, hills and valleys, or of plains. It is diversified by forest, wood, or copse; and watered by rivers, rivulets, lakes, and pools. Those parts that are not clothed with wood are either open or inclosed, forming grassy downs, heaths, pastures, meadows, morasses, and arable land. The soil also is equally various:--we find clay, loam, marl, chalk, vegetable mould, moor, sand, &c. The mountains and hills are either covered with a stratum of soil, or are rocky and bare; the arable lands are divided by living or dead fences, the latter formed of various materials,--or else they are open, and the property only marked out by grassy balks, &c. All these places abound in shrubs and plants; some local, and some generally distributed. But besides the _land_ and its _fresh_ waters, we must look also to the _sea_, and its sandy, pebbly, or rocky shores, and the sea-wrack that is cast up upon them; the _estuaries_ that receive its tides; the brackish waters and saline marshes in its vicinity. All the above places, when opportunity serves, the Entomologist should explore, for in almost all he will find peculiar kinds of insects.

As _mountains_ and _hills_ have usually their own Flora, the insects appropriated to alpine plants can only be met with where the pabulum is found. Here also those northern insects that are impatient of a warmer climate will take their station, if they migrate to the southward[1518]. The predaceous beetles likewise sometimes frequent a mountainous district. _Carabus glabratus_ was first taken by Professor Hooker on Ingleborough; and probably, if the Welsh and Scotch mountains were duly investigated by an Entomologist, many novelties would reward his toils. The _valleys_ and _plains_, especially those of a sunny exposition, abound in insects. When the heat of the atmosphere indisposes you for motion, you will find it no unprofitable or unpleasant employment, lying on the grass, to search for minute beetles, which you will there find coursing about amongst the tufts and roots of the herbage. Thus you may procure many of the _Pselaphidæ_, which you would not otherwise meet with. Even when the grass is grown up, insects are fond of alighting upon its spikes, and thence drop or run to the ground. Should circumstances ever carry you abroad to the steppes or grassy plains of Tartary, or to Hungary, you would find there two or three species of the singular genus _Lethrus_, which burrows in the soil. Every hole is inhabited by a male and female;--from it they issue to attack the plants or vines; and having cut out the heart of a plant, go backwards like a crab with the prize to their burrow. At the time of pairing, sometimes violent battles, encouraged by the female, take place between the male and a stranger of that sex desirous of admission, which cease only with the death or flight of the stranger[1519]. The vicinity and borders of _woods_ generally abound in insects of every Order; and if you proceed, as hereafter directed, will furnish you with numerous prizes, especially of _Lepidoptera_. Here alone you can meet with the purple emperor butterfly (_Apatura Iris_); and if properly equipped you may readily secure him.

The _waters_ you will find nearly as prolific in insects as the land. In them, amongst the beetles, you may expect to meet with _Dytiscus_, _Haliplus_, _Pælobius_, _Hyphydrus_, _Hydroporus_, _Noterus_, _Colymbetes_, and other _Dytiscidæ_; the _Gyrini_, _Hydrophili_, _Hydrænæ_, _Elophori_, &c.: under stones, the _Elmis_; and in the mud, the _Parni_ and _Heteroceri_. Some _Sphæridiadæ_ are also aquatic: I have taken more than once _Cercyon hæmorrhoidale_ from the under side of a piece of wood immersed in a canal[1520]. Even a few of the weevil tribes are to be met with in water. _Lixus paraplecticus_, _Tanysphyrus Lemnæ_, _Bagous atrirostris_, are of this description. A species of _Ceutorhynchus_ of Germar's _third_ family (_C. Natator_ K.) _swims_ well. On aquatic plants you must look for _Helodes_ and the splendid _Donaciæ_, which, living on submerged shoots and roots of these plants in their larva state, continue to attend them when perfect. Amongst the _Eutrech_in_a_[1521],--_Elaphrus_, _Notiophilus_, and _Bembidium_ frequent humid places, as the banks of rivers and ponds; and in such a station, under the roots of _Potentilla anserina_, _Polygonum_, &c. if you should be fortunate enough to find _Omophron limbatum_, which connects the _Eutrech_in_a_ with the _Eunech_in_a_, you will make a valuable addition to the list of British insects. In the waters also you will meet with many Heteropterous _Hemiptera_; as _Gerris_, _Hydrometra_, and _Velia_, and all the _Hydrocorisæ_ or water-bugs. On aquatic plants the larvæ of some _Lepidoptera_ feed, as _Hydrocampa stratiotata_, _potamogata_, &c. Those also of the _Trichoptera_ must be sought for in the water: and if you should feel inclined to see an interesting collection of their very curious _cases_, Mr. Sheppard of Wrabness can gratify your curiosity. Though few or no _Hymenoptera_ frequent this element, vast numbers of _Diptera_ are there alone to be met with in their preparatory state, particularly the gnats. We learn from Humboldt a curious fact with respect to those of South America, or the _Zancudos_; that, with some exceptions, these pests do not frequent those rivers called by the natives _black waters_, but only those which they name _white waters_[1522]. Of the _Aptera_, the genera _Hydrachna_, _Eylaïs_ and _Limnochares_ are purely aquatic. Several spiders will walk over the water; and one species (_Argyroneta aquatica_) inhabits it[1523]. The _stagnant_ waters in your vicinity will produce different species from _running_ ones. Thus _Haliplus elevatus_, &c. inhabits only the _latter_, while the majority of the _Dytiscidæ_ abound most in the _former_: the more minute ones may be sought for with success amongst the duckweed that covers a pool. I do not recollect finding any insect in waters absolutely _salt_[1524]; but _brackish_ waters produce peculiar species: in these only, _Hydræna marina_ occurs; and many of those large-eyed _Cimicidæ_ (_Acanthia_), as _A. saltatoria_, _littoralis_, and _Zosteræ_ occur in places where salt water has been. Latreille observes, that the genus _Pimelia_ is to be met with only where the soil is impregnated with saline particles, or where the species of the genus _Salsola_ abound[1525].

_Heaths_, though they do not afford numerous insects, have their rarities. _Cicindela sylvatica_, _Carabus nitens_ and _arvensis_, frequent them, and are not elsewhere to be seen. _Curculio nebulosus_ is also to be found on them, in places where the turf has been peeled; and some scarce _Lepidoptera_. In their vicinity, in sunny sandy banks, some of the rarer _Ammophilæ_ and _Pompili_ may be taken; and it is here only that I have ever met with _Panurgus_[1526]. _Meadows_ and _pastures_ are not to be neglected. Early in the year, when they are yellow with the blossoms of _Ranunculus bulbosus_, _Leontodon Taraxacum_, &c., many minute beetles, and not a few _Hymenoptera_ and _Diptera_, frequent them. _Morasses_ also have their peculiar insects. In these you will meet with some of the scarcer _Eutrech_in_a_; as _Chlænia holosericea_ and _nigricornis_, _Blethisa multipunctata_, various _Bembidia_, &c. In this kind of district in the Isle of Ely _Aphodius plagiatus_ has been taken, and that scarce and beautiful butterfly _Lycæna Virgaureæ_. Where land is _cultivated_ the Entomologist as well as the farmer may expect a _harvest_. Insects in general are fond of perching on the summit of a blade of grass or corn; and many minute ones may be taken coursing about in the ears of the latter: some to devour the _fungilli_ that infest the grain, as _Phalacrus corruscus_ in _Reticularia Segetum_; others to attack the grain itself, as _Cecidomyia Tritici_; others to destroy these destroyers, as three little parasites belonging to the _Chalcidites_[1527]. But I have already mentioned most of those insects that are to be expected in such situations[1528]: I shall therefore only further observe, that upon _barley_ particularly you will meet with the species of Latreille's genus _Cephus_.

With respect to _soils_, those that are _light_ appear to be most prolific in insects. Warm _sandy_ banks are frequented by _Cicindela campestris_, _Opatrum sabulosum_, _Helops quisquilius_, &c.: in them (when of a southern aspect) _Ammophilæ_, _Pompili_, and numerous _Hymenoptera_ nidificate. _Chalk_ also attracts various insects. Latreille observes, that the _Licini_, _Papilio Cleopatra_, several species of _Dasytes_, and some _Lamiæ_, delight in this kind of soil[1529]:--in my own neighbourhood I have observed _Polyommatus Corydon_ principally in chalk-pits. One of these pits, under a wood in an adjoining parish, has produced me several valuable insects. Here I took _Apion ebeninum_, _Orobitis globosus_, a new species of _Evæsthetus_, several of the rarer _Pselaphidæ_ and _Cholevæ_, and _Chætophorus cretifer_ before noticed[1530]. I do not mean, however, that all these are properly _chalk_ insects; but they fall into these pits, where they are readily discerned, from the contrast of their colours with the whiteness of the chalk. By watching attentively the bottom of one, vast numbers in a warm day may be taken when they fall or are climbing upwards. Of all soils _clay_ offers the fewest inducements to the Entomologist, who will lose both his time and labour in a clay-pit; while in one of sand, chalk, or marl, they will usually not be mispent. _Vegetable earth_ also affords a harbour to various larvæ, and the pupæ of many nightfliers amongst the _Lepidoptera_, by digging in it, especially under trees, may be obtained. Even the bare _rocks_ have their insect frequenters that take shelter in their fissures; and in the early part of your career especially you should always turn over large stones, as beneath them many of the _Harpalidæ_ and other _Eutrech_in_a_ frequently lie hid: and in this situation, both in Suffolk and Sussex, _Lomechusa emarginata_, one of our scarcest _Brachyptera_, has been taken. Old trees also, and planks that have laid long without being moved, often afford a shelter to many of the minute _Coleoptera_; as _Pselaphidæ_, _Aleocharidæ_, _Cryptophagidæ_, _Scymnidæ_, &c. _Live_ fences, especially when the hawthorn is in blossom, and where trees are also intermixed, are attended by innumerable insects of almost every description; and even the black-thorn will present you with one of our most splendid weevils (_Rhynchites Bacchus_). _Dead_ fences are almost as fertile in insects as living ones. In _gates_, _posts_, _rails_, and other _timber_ when felled, the timber-devouring tribes take their station:--between the bark and the wood are the _Bostrichidæ_; in the wood itself, the _Anobidæ_ and the Capricorn beetles. Here also you may meet with many _Hymenoptera_, which either devour timber or nidificate in it,--as the _Siricidæ_, _Chelostoma_, _Trypoxylon_, _Sapyga_, and several _Diptera_. In the decaying hedgestakes and sticks, where the _Sphæria decorticans_ has turned off the bark, you may meet with _Anthribus brevirostris_; with _A. latirostris_, and other beetles, in _S. fraxinea_; and _A. albinus_, which I have more than once captured as it was emerging from the fissure of a gate-post, probably feeds on some internal fungus. The grassy _balks_ that separate open fields usually abound in umbelliferous plants, which are attended by numerous _Hymenoptera_ and _Diptera_, particularly by the various species of the splendid tribe of _Chrysidæ_: and the grassy banks of fences, where the aspect is sunny, are generally bored by a variety of insects of the former Order, to prepare a nest for their young. _Andrenidæ_ and _Nomadidæ_ particularly select this situation, the latter probably depositing their eggs in the burrows of the former[1531]. By watching these places in the spring, you may perhaps have the good fortune to meet with a _Stylops_. It is singular, that some insects choose, for their own residence or that of their young, the hardest and most trodden pathways. Thus, some ants will build their subterranean apartments under gravel walks; and so do many species of the genus _Halictus_[1532], the habits and economy of which have been so ably detailed by M. Walckenaër[1533]: _Cerceris_ also, and other _Hymenoptera_, will choose such places, however public, for the site of their nests or burrows. The ground is so consolidated by the constant foot, that they, probably find such situations spare them a world of labour, and therefore in their choice balance one inconvenience by another.

Though the _sea_ itself, I believe, produces no true _insects_, yet there are many that constantly or occasionally haunt its shores. On the sand-hills of the Norfolk coast I found _Ægialia globosa_ and _Cicindela hybrida_. _Ceutorhynchus horridus_ inhabits thistles that grow near the sea. Under the _Zostera_ and _Fuci_, (cast up both on its beach and the shores of estuaries,) many peculiar species of _Cercyon_, several _Aphodii_, and numerous _Brachyptera_, may often be found. In this situation the rare and singular _Bledius armatus_ has been taken. At certain seasons of the year the beach and environs of the sea are covered by many species of _Coccinella_, which seem to bend their course thither from the inland country, as if they were about to emigrate[1534]. When the weather is fine and the tide begins to retire, at the line of its highest rise I have taken on the eastern coast a variety of insects, and amongst the rest _Anomala Frischii_. The inundations of rivers, except in the depth of winter, always bring a number of these little creatures, which float on the surface on bits of stick, weeds, &c.; and where they deposit these articles when the water begins to subside, you may generally reap a plentiful harvest of various kinds.

You see, now, how varied is the scenery to which the diversion of the Entomologist introduces him; that he is never out of his way: whether on hill or in valley; on upland or plain; on the heath or in the forest; on the land or on the water; in the heart of a country or on its shores;--still his game is within his reach. But in order to enable him to pursue it with greater prospect of success, he must recollect that not only is every face of the country to be explored, but both the _plants_ and the _animals_ that it produces; and that he must not turn with disgust from even the _carcase_ or the _excrement_ of the latter. As numerous species of herbivorous insects feed only on _one_ kind of plant, the Entomologist, when he discovers a scarce one, should examine it with the hope of finding upon it a scarce insect. Sometimes it happens that only a single opportunity occurs in a man's life of seeing certain plants growing wild: such opportunities should never be neglected. Some insects also inhabit a plant in one district or season, and not in another. Thus the most beautiful of the Apions, _A. Limonii_[1535], though the plant it feeds upon usually abounds near the sea, I have discovered only on the northern coast of Norfolk; and another scarcely less beautiful, but more minute (_A. Astragali_[1536]), though I have sought for it year after year, _Astragalus glyciphyllus_ being abundant near me, I never found but once. The blossoms of plants as well as the leaves must be inspected. In those of the rose, the _Cetonia aurata_ is often taken[1537]; and in the bells of the different species of _Campanula_ various bees may be captured enjoying a luxurious repose[1538]. No vegetable productions abound more in insect inhabitants than the _Fungi_. In Agarics several _Diptera_ are to be taken, many _Aleocharæ_, _Oxypori_, &c.; in Boleti, the various species of _Mycetophagus_; in the arboreous ones, and under bark, more than one kind of _Ips_; and in _Auricularia_, as well as _Boletus_, the whole genus _Cis_. Upon _living_ Vertebrate animals you must look for _Pulices_, _Pediculi_, _Nirmi_, _Acari_, and many _Diptera_, as _Œstrus_, _Tabanus_, _Stomoxys_, and the _Pupipara_ of Latreille; and on the garden-snails for that curious genus _Drilus_, and some _Acari_[1539]. The caterpillars and pupæ of _Lepidoptera_, &c. will, as you have heard, furnish you with numerous ichneumons[1540]. On _dead_ animals you will find the various species of _Silphidæ_, _Nitidulidæ_, _Dermestidæ_, _Byrrhidæ_, _Chlolevidæ_, _Staphilinidæ_, _Muscidæ_, &c.; and in excrement, various _Scarabæidæ_, _Histeridæ_, _Aphodiadæ_, _Sphæridiadæ_, the _Brachyptera_ in general, and several _Diptera_[1541]. In putrescent roots and fruits, as the turnip, the cucumber, &c., you may also occasionally meet with rare _Coleoptera_.

* * * * *

I must next say something upon the _seasons_ of insects, and their times of appearance. Those that collect honey and pollen are generally among the first that proclaim the approach of spring; and their appearance may be dated from the blossoming of certain trees and plants of common occurrence. Other plants, accompanied by peculiar insects, blossom later; and so on till we arrive at the autumn. The _earliest_ insect-season commences with the flowering of the _sallow_ (_Salix Caprea_) usually accompanied in the garden by that of the _crocus_ and the _gooseberry_. Then is your time to collect many species of wild bees and _Diptera_ not afterwards to be met with: and various other insects now begin to emerge from their winter-quarters, or are produced from the pupa. _Another_ and later season is marked by the general blossoming of the butter-cup (_Ranunculus bulbosus_), accompanied by the marsh-marygold (_Caltha palustris_) and ladies'-smock (_Cardamine pratensis_); when you may hunt the pastures, meadows, and marshes with success, and take some insects that do not show themselves later. The coprophagous insects are now abundant. Amongst others, _Aphodius testudinarius_, a perfectly _vernal_ species, is now only to be taken, and usually flying. A _third_ insect-season indicated by Flora, and a very prolific one, commences with the blossoming of the _hawthorn_, when you must desert the meads for the inclosures. At this time all nature begins to put on her gayest attire, and all her insect tribes are now on the alert, and fill the air. They are almost universally attracted by the sweet and lovely blossoms of the plant just named: so that by examining them you may entrap some of every Order, and many that during the year will appear no more. Even many of the saprophagous insects will sip nectar from these flowers. The _umbelliferous_ plants proclaim the _fourth_ season of insects, particularly the wild _carrot_ and _parsnip_. You will scarcely ever fail to find, if the weather is genial, _Hymenopterous_ and _Dipterous_ insects of various genera,--especially such as have a _short_ tongue,--engaged in collecting the honey from those plants. Here you may take some of the rarer _Chrysidæ_, _Crabronidæ_, _Cercerides_, &c., and occasionally even _Coleoptera_. The _last_ insect-season may be dated from the general flowering of the _thistle_ tribe. When these are in blossom is the best time of all to collect the _humble-bees_ (_Bombus_[1542]), the leaf-cutter bees (_Megachile_[1543]), and many other _Apiariæ_, which alone by their long tongues can imbibe the honey and collect the pollen of these flowers. The male humble-bees frequent them to the last, and often seem as if they were intoxicated with their sweets.

But perhaps you may prefer considering the whole summer appearance of insects as divided into _three_ principal seasons. This may thus be done. Their _vernal_ season may commence _Florente Caprea_, and end _Florente Oxyacantha_; their _summer_, _Florente Oxyacantha_ and _Florentibus Umbellatis_; their _autumn_, _Florentibus Umbellatis_ and _Florente Carduo_. In the _first_, the number of insects will be daily _increasing_; in the _second_ (which is the harvest of the Entomologist, when his eyes and his hands ought to be every where), they will reach their _utmost complement_; and in the _third_, they will be gradually decreasing in number, till they generally die, or go into winter-quarters. At this time many minute _Diptera_ and Ichneumons take shelter from the weather in the windows of our apartments. These seasons will not always exactly correspond with our usual reckoning, and take place at the same time; since, being regulated by our varying temperature, they will be sometimes sooner and sometimes later, sometimes longer and sometimes shorter. Though I have not named a _brumal_ season, because insects are in winter usually torpid,--yet some, as _Diurnea Novembris_, _Cheimatobia brumata_, and many _Tipulariæ_, even then make their appearance.

If you ask, Whether it be not possible to regulate our Entomological seasons by the appearance of insects themselves? I should answer, that probably this might be done; but that further observations seem wanted to enable us to do it satisfactorily. Perhaps the appearance of _Formica rufa_ beginning the business of the year might form the commencement of one season; the flight of the orange-tip butterfly (_Pontia Cardamines_[1544]), of a second; a third might be indicated by the swarming of _Melolontha vulgaris_; a fourth, by that of _Amphimalla solstitialis_; and the last, by the appearance in numbers of _Aphodius ciliaris_, which in the autumn fills every horse-dropping.

Some insects are so ephemeral, that they are to be found in numbers only for a few days, and then disappear for that season. Of this description are the _Ephemeræ_, much of whose history has been detailed to you. Those of which De Geer has given an account (_E. vulgata_) appeared about the end of May or the beginning of June, and continued about a _fortnight_[1545]; while those which Swammerdam observed did not come forth till the middle of June, and lasted only _three_ days[1546]. The _same_ period distinguished those of which Reaumur has compiled so interesting a history, but they did not show themselves before the middle of August[1547]. My kind friend Mr. Marsham not long before his death copied for me some memoranda he had made with respect to the sudden appearance of _Cercopis bifasciata_. On one occasion the white dress of a lady sitting upon a haycock was covered by these insects; but on the following day the same steps were taken at the same time to procure some, when after the most diligent search not a single one could be found. The same circumstance was observed a few years afterwards by another friend of his. He himself was of opinion that the insects in question were then migrating[1548].

I may here observe, that the London amateurs have particular _seasons_ for collecting _moths_. For the _imago_ they go into the woods in _April_, _May_, _June_, and _October_. For the _larvæ_ they take the beginning of _April_, _June_, the beginning of _July_, and _September_. They dig for _pupæ_ late in _July_, and in _January_ and _February_.

* * * * *

I shall lastly make a few observations upon the _times_ of _action_ and _repose_ of insects, the knowledge of which, as far as it can be obtained, is of essential use to the industrious collector. Entomologists have divided the _Lepidoptera_, with a view to this circumstance, into _diurnal_, _crepuscular_, and _nocturnal_; or butterflies (_Papilio_ L.), hawkmoths (_Sphinx_ L.), and moths (_Phalæna_ L.). These terms may be applied to insects in general.

i. _Diurnal_ insects are abundant. _Butterflies_ in particular fly generally at no other time: they accompany the sun in his course, and before he sets disappear. Some other _Lepidoptera_, though not so named, are _day_ insects:--such are the _Zygænidæ_, &c. amongst the hawkmoths; and amongst the moths, _Plusia Gamma_, the _Phytometræ solares_ of Haworth[1549], and some others. Numberless _Coleoptera_ belong to this section. The _Donaciæ_ fly only when the sun is out and the air is warm; they are then extremely agile and difficult to take. Some _Hopliæ_ swarm in the day before noon, and then disappear[1550]: most of the _tetramerous_ beetles also appear to be diurnal. The _Libellulina_ and many other _Neuroptera_ may also be so termed; and the _Hymenoptera_ almost universally, with the sole exception of the _Formicidæ_[1551]. Amongst the _Diptera_, if we leave out the _Tipulariæ_, the rest will be found for the most part to belong to the present section.

ii. _Crepuscular_ insects, strictly speaking, are those that appear only during the twilight, whether in the morning or evening; but the term may be understood, with some latitude, to signify all those insects that are seen only in the morning and evening, though after sunrise and before sunset. Of these, some come forth only in the _morning_, others only in the _evening_, and others both _morning_ and _evening_. My memory only furnishes me with a single instance of an insect whose principal appearance and flight are in the _morning_. _Catocala nupta_ I have often seen flying at this time, about six or seven o'clock, and never at any other: I am not however prepared to assert that it does not appear in the evening or night, but I have then never met with it. In the _evening_ more particularly you hear the hum of the dung-beetle (_Geotrupes_), which Linné thought the prognostic of a following fine day; and of the swarms of _Melolontha vulgaris_ and _Amphimalla solstitialis_. Then also many other _Coleoptera_ are in the air; especially before a thunderstorm, a state of the atmosphere that particularly excites insects[1552]: _Ptinus imperialis_ and _germanus_ I have never taken except under these circumstances. Then the _Ephemeræ_ sport in the air, and lead their mystic dance. The majority of the hawkmoths are then too on the wing, with their long tongues imbibing the nectar of the flowers while they hover over them, both _morning_ and _evening_.

iii. In the _night_ the main body of the _moths_ take their flight, as well as a vast number of _Coleoptera_ and insects of other orders. At this time the _Blattæ_ and crickets leave their hiding-places and run about: but the other _Grylli_ L., though they sing in the night, fly only in the day. Then also the _Carabi_, like beasts of prey, leave their dark retreats,--in this differing from the _Cicindelæ_, which are diurnal,--and prowl about to entrap other unwary insects. Then, likewise, the female glowworm hangs out her lamp of love, and the male, led by it, wings his way to her: and then the water-beetles (_Dytisci_, _Gyrini_, &c.) forsake the waves and become tenants of the air.

Could we with certainty discover the stations in which insects after their excursions take their _repose_, we might capture many that we now search for in vain. Several of these stations were pointed out in a former part of this letter where I detailed their usual _haunts_. I may here add, that numbers of them, when reposing, conceal themselves from their enemies on the under side of the leaves of trees and plants. Moths, especially the _Noctuidæ_, may often be met with in woods, as before observed[1553], on the _north_ side of the trunks of trees. Mr. Marsham related to me, that once a little before sunset, observing over his head a number of insects on the wing moving on in one direction, he caught some of them, and they proved to be _Labia minor_. Struck with the circumstance, he watched them several evenings; and on one, as he was looking about a melon-pit for insects, he saw these little animals alight on the frame, hastily fold up their wings, and entering under the glasses, run down its sides and bury themselves in the loose earth. This he observed repeatedly. The onward flight of these insects was therefore evidently their return from their diurnal cruise to their nocturnal station.--This happened in September.

I am, &c.

FOOTNOTES:

[1458] Linn. _Philos. Botan._ § 334.

[1459] _Linn. Trans._ x. 20--. &c. _Dict. des Scienc. Nat._ xviii.

[1460] _Selborne_ i. 173.

[1461] _Philos. Entomolog._ ix. § 20.

[1462] _Mém. du Mus._ 1815.

[1463] _Hor. Entomolog._ 42--. 518.

[1464] _Essai Elément. de Géograph. Botan._ 62.

[1465] _Wisdom of God_, &c. 2d edit. 9.

[1466] _Hor. Entomolog._ 469. This calculation includes the _Crustacea_.

[1467] It has lately been discovered that the larva of _Drilus flavescens_, a beetle, feeds upon the common snail. (_Bulletin des Scienc. Nat._ 1824. iii. 297; v. 110; vi. 221.) I have found an _Acarus_ on the same animal.

[1468] See above, p. 219--.

[1469] We employ this term, because the more common one, _herbivorous_, does not properly include devourers of timber, fungi, &c.

[1470] If we consider the number of species of _Acari_, _Nirmi_, _Poduræ_, and _Araneidæ_, this proportion will appear moderate.

[1471] _Hor. Entomolog._ 48.

[1472] _Philos. Entomolog._ ix. § 20.

[1473] _Géograph. Génér. des Ins._ 5.

[1474] _Ibid._

[1475] _Ibid._ 7--.

[1476] _Ibid._ 8, 11.

[1477] _Personal Narrat._ E. T. v. 88. He says also that each stream almost has its peculiar species (_Ibid._ 98), and that they sometimes emigrate to stations they had not infested before. _Ibid._ 106--.

[1478] _Hor. Entomolog._ 519.

[1479] Latr. _ubi supr._ 3.

[1480] _Géographie_, &c. 22--.

[1481] _Ibid._ 27.

[1482] _Géographie_, &c. 20--.

[1483] See above, p. 494.

[1484] As this insect is the type of a distinct genus amongst the _Scutelleridæ_, I have distinguished it by the name Fabricius gave the whole tribe.

[1485] M. Latreille (_Géographie_, &c. 8.) seems to regard these varieties as _distinct_; in which case they would be the _representatives_ of the species named in the text: but the variations are mostly so slight, as not to afford any satisfactory distinctive characters.

[1486] _Géogr. Génér. des Ins._ 2.

[1487] When I described the Melville Island insects for Captain Sabine, I received from him no _Culices_; but I afterwards saw in his possession a genuine one from thence.--K.

[1488] _Linn. Trans._ xii. 380--. n. 6, 7.

[1489] _Ibid._ n. 5.

[1490] Dejean in his catalogue gives only 434 species; while Mr. Stephens, _four_ years ago, had 550, and has since increased the number to above 600.

[1491] _Journal of a Tour in Iceland_, 272.

[1492] VOL. I. p. 115--.

[1493] _Entomogr. Russ._ Coleopt. _t._ xiii. _f._ 1.

[1494] Ahren's _Fn. Europ._ i. 1.

[1495] _Hor. Ent._ 47--.

[1496] _Annulosa Javanica_, 36.

[1497] See the Rev. L. Guilding's admirable _History_ of _Xylocopa Teredo_ and _Horia_ (_Cissites_ Latr.) _maculata_, Linn. Trans, xiv. 313--.

[1498] Out of 51 species described by Bilberg, 28 are African, and 19 of these are from the Cape.

[1499] _Géogr. Génér. des Ins._ 18.

[1500] _Hor. Entomolog._ 45.

[1501] Dr. Leach has described 8 British species (_Linn. Trans._ xi. 37.); Dejean has 7 Spanish ones.

[1502] I have a very splendid species of this genus taken by C. C. Elwes Esq. on the Pyrenees, which is undescribed, and falls under none of the count Dejean's Families, having its elytra perfectly smooth, without striæ, punctures, &c. It is of a brilliant golden green. It stands in my cabinet under the name of _C. lævigatus_. K.

[1503] Fischer _Entomogr. Russ._ 90--. _t._ viii. _f._ 13.

[1504] VOL. III. p. 562.

[1505] Major General Hardwicke gave me one of this description from Nepal.

[1506] Latr. _Géograph._ &c. 18--.

[1507] _Linn. Trans._ xiv. _t._ iii. _f._ 4.

[1508] _Hor. Entom._ 147.

[1509] _Linn. Trans._ ubi supr. _f._ 1.

[1510] _Ibid._ xii. _t._ xxi. _f._ 9.

[1511] _Ibid._ _f._ 14.

[1512] To this genus belong _Melolontha aurulenta_. Ibid. 400; and _M. sericea_. Ibid. 463.

[1513] Latr. _Géograph._ 7.

[1514] _Cetonia atropunctata_ and _Brownii_ of _Linn. Trans._ (xii. 464. _t._ xxiii. _f._ 6.) belong to this genus.

[1515] _Linn. Trans._ xii. _t._ xxii. _f._ 2; _t._ xxiii. _f._ 7.

[1516] Latreille, _Géograph._ &c. 10.

[1517] _Linn. Trans._ xiv. 569.

[1518] See above, p. 496.

[1519] Fischer, _Entomogr. Russ._ i. 135.

[1520] From finding it in water, Fabricius considered this insect as a _Hydrophilus_, but it is a true _Cercyon_.

[1521] See above, p. 401.

[1522] _Personal Narrat._ E. T. v. 91--.

[1523] See VOL. I. p. 470--.

[1524] A species of _Gyrinus_ (_G. Viola aquatica_), described by Modeer (_Linn. Syst. Nat._ Ed. Gmel. i. 1612. n. 9.), is said to inhabit _salt_ water.

[1525] _Géograph._ &c. 6.

[1526] _Apis_ *., a. _Mon. Ap. Angl._ ii. 178--.

[1527] _Linn. Trans._ iv. 30--. v. 96--. _t._ iv.

[1528] VOL. I. LETTER VI.

[1529] _Géograph._ &c. 6.

[1530] VOL. II. p. 255.

[1531] These, as well as _Melecta_, are probably a kind of _Cuckow_-bee. _Mon. Ap. Angl._ i. 150.

[1532] _Melitta_ * *. b. _Mon. Ap. Angl._ i. 138--.

[1533] _Mémoires sur le gènre_ Halicte.

[1534] VOL. II. p. 9.

[1535] _Linn. Trans._ ix. 78--. _t._ i. _f._ 20.

[1536] _Ibid._ 55. _t._ i. _f._ 12.

[1537] This insect does not, I believe, eat the petals of the rose, but _laps_ the nectar it produces. I have seen it employed upon wounded trees lapping the sap.

[1538] _Mon. Ap. Angl._ ii. 172. 257.

[1539] See above, p. 491, note^a.

[1540] _Ibid._ p. 219; and VOL. I. p. 267--.

[1541] _Ibid._ p. 256--.

[1542] _Apis_ * *. e. 2. K.

[1543] _Apis_ * *. c. 2. α. K.

[1544] _Butterfly Collector's Vade Mecum_, 66, note^d.

[1545] De Geer ii. 638--. 641--.

[1546] Swamm. _Bibl. Nat._ i. Conf. 114 with 103.

[1547] Reaum. vi. 480--.

[1548] VOL. II. p. 11.

[1549] _Lepidopt. Britann._ 263--.

[1550] _Linn. Trans._ v. 256.

[1551] VOL. II. p. 95--.

[1552] See above, p. 254--.

[1553] VOL. II. p. 217. See above, p. 200.