Chapter VIII: Hemiptera, or Bugs—anoplura 532 (12)

FAM. 75. CANTHARIDAE OR MELOIDAE (_Blister-beetles_, _Oil-beetles_).-_-Head with an abrupt neck; elytra and sides of the abdomen without any coadaptation; each claw of the feet with a long appendage closely applied beneath it._ This distinct family consists of Heteromera with soft integument, and is remarkable for the fact that many of its members contain a substance that when extracted {270}and applied to the human skin, possesses the power of raising blisters. The life-history is highly remarkable, the most complex forms of hyper-metamorphosis being exhibited. The species now known amount to about 1500; there can be no difficulty in recognising a member of the family by the above characters, except that in a very few cases each claw bears a projecting tooth, instead of an elongate appendage parallel with itself. The penultimate tarsal joint scarcely ever broader than the preceding; the colour and style of markings are extremely varied. There are two very distinct sub-families, Cantharides and Meloides; the former are winged Insects, and are frequently found on flowers or foliage. The Meloides are wingless, and consequently terrestrial; they have a very short metasternum, so that the middle coxae touch the hind; and they also have very peculiar wing-cases, one of the two overlapping the other at the base; in a few Meloids the wing-cases are merely rudiments.

The post-embryonic development of these Insects is amongst the most remarkable of modern entomological discoveries. The first steps were made by Newport in 1851,[140] and the subject has since been greatly advanced by Fabre, Riley, and others. As an example of these peculiar histories, we may cite Riley's account[141] of _Epicauta vittata_ (Fig. 140), a blister-beetle living at the expense of North American locusts of the genus _Caloptenus_. The locust lays its eggs underground, in masses surrounded by an irregular capsule, and the _Epicauta_ deposits its eggs in spots frequented by the locust, but not in special proximity to the eggs thereof. In a few days the eggs of the blister-beetle hatch, giving rise to little larvae of the kind called triungulin (Fig. 140, A), because each leg is terminated by three tarsal spines or claws. In warm, sunny weather these triungulins become very active; they run about on the surface of the ground exploring all its cracks, penetrating various spots and burrowing, till an egg-pod of the locust is met with; into this the triungulin at once eats its way, and commences to devour an egg. Should two or more triungulins enter the same egg-pod, battles occur till only one is left.

{271}

After a few days passed in devouring a couple of eggs, the triungulin sheds its skin and appears as a different larva (Fig. 140, B), with soft skin, short legs, small eyes, and different form and proportions; a second moult takes place after about a week, but is not accompanied by any very great change of form, though the larva is now curved, less active, and in form like a larva of Scarabaeidae; when another moult occurs the fourth instar appears as a still more helpless form of larva (Fig. 140, D), which increases rapidly in size, and when full grown leaves the remains of the egg-pod it has been living on, and forms a small cavity near by; here it lies on one side motionless, but gradually contracting, till the skin separates and is pushed down to the end of the body, disclosing a completely helpless creature that has been variously called a semi-pupa, pseudo-pupa, or coarctate larva (Fig. 140, C); in this state the winter is passed. In spring the skin of the coarctate larva bursts, and there crawls out of it a sixth instar which resembles the fourth (Fig. 140, D), except in the somewhat reduced size and greater whiteness. It is worthy of remark that the skin it has deserted retains its original form almost intact. In this sixth instar the larva is rather active and burrows about, {272}but does not take food, and in the course of a few days again moults and discloses the true pupa (Fig. 140, E). As usual in Coleoptera this instar lasts but a short time, and in five or six days the perfect beetle appears (Fig. 140, F). It is extremely difficult to frame any explanation of this complex development; there are, it will be noticed, no less than five stages interposed between the first larval instar and the pupal instar, and the creature assumes in the penultimate one a quasi-pupal state, to again quit it for a return to a previous state. It is possible to look on the triungulin and the pupal instars as special adaptations to external conditions; but it is not possible to account for the intermediate instars in this way, and we must look on them as necessitated by the physiological processes going on internally. Nothing, however, is known as to these. It may be well to mention that, after describing and figuring (_loc. cit._) this series of instars, Riley changed his views as to their nomenclature.[142] The following summary of the metamorphosis, to which we have added the two nomenclatures of Riley—the original one, when different from the amended one, being given in square brackets—may therefore be useful, viz.—Egg; 1, triungulin-larva—moult; 2, Caraboid larva [second larva, Caraboid stage]—moult; 3, Scarabaeoid larva [second larva, Scarabaeoid stage]—moult; 4, Scarabaeoid larva [second larva, ultimate stage] (large amount of food and much growth)—moult; 5, coarctate larva [pseudo-pupa, or semipupa]; 6, Scolytoid larva [third larva] (active, but little or no food taken)—moult; 7, pupa—moult; 8, perfect Insect.

M. Fabre has succeeded in elucidating the history of _Sitaris humeralis_, a Cantharid that lives at the expense of bees of the genus _Anthophora_.[143] The eggs of the _Sitaris_ are deposited in the earth in close proximity to the entrances to the bees' nests, about August. They are very numerous, a single female producing, it is believed, upwards of 2000 eggs. In about a month—towards the end of September—they hatch, producing a tiny triungulin of black colour; the larvae do not, however, move away, but, without taking any food, hibernate in a heap, remaining in this state till the following April or May, when they become active. Although they are close to the abodes of the bees they do not enter them, but seek to attach themselves {273}to any hairy object that may come near them, and thus a certain number of them get on to the bodies of the _Anthophora_ and are carried to its nest. They attach themselves with equal readiness to any other hairy Insect, and it is probable that very large numbers perish in consequence of attaching themselves to the wrong Insects. The bee in question is a species that nests in the ground and forms cells, in each of which it places honey and lays an egg, finally closing the receptacle. It is worthy of remark that in the case of the _Anthophora_ observed by M. Fabre, the male appears about a month before the female, and it is probable that the vast majority of the predatory larvae attach themselves to the male, but afterwards seize a favourable opportunity, transfer themselves to the female, and so get carried to the cells of the bee. When she deposits an egg on the honey, the triungulin glides from the body of the bee on to the egg, and remains perched thereon as on a raft, floating on the honey, and is then shut in by the bee closing the cell. This remarkable act of slipping on to the egg cannot be actually witnessed, but the experiments and observations of the French naturalist leave little room for doubt as to the matter really happening in the way described. The egg of the bee forms the first nutriment of the tiny triungulin, which spends about eight days in consuming its contents; never quitting it, because contact with the surrounding honey is death to the little creature, which is entirely unfitted for living thereon. After this the triungulin undergoes a moult and appears as a very different creature, being now a sort of vesicle with the spiracles placed near the upper part; so that it is admirably fitted for floating on the honey (Vol. V. Fig. 86, 10). In about forty days, that is, towards the middle of July, the honey is consumed, and the vesicular larva after a few days of repose changes to a pseudo-pupa (11 of the fig. cited) within the larval skin. After remaining in this state for about a month, some of the specimens go through the subsequent changes, and appear as perfect Insects in August or September. The majority delay this subsequent metamorphosis till the following spring, wintering as pseudo-pupae and continuing the series of changes in June of the following year; at that time the pseudo-pupa returns to a larval form (12 of the fig. cited), differing comparatively little from the second instar. The skin, though detached, is again not shed, so that this ultimate larva is enclosed in two {274}dead skins; in this curious envelope it turns round, and in a couple of days, having thus reversed its position, becomes lethargic and changes to the true pupa, and in about a month subsequent to this appears as a perfect Insect, at about the same time of the year as it would have done had only one year, instead of two, been occupied by its metamorphosis. M. Fabre employs the term, third larva, for the instar designated by Riley Scolytoid larva, but this is clearly an inconvenient mode of naming the instar. _Sitaris humeralis_ is now very rare in Britain, but it seems formerly to have been more common, and it is not improbable that its triungulin may have been the "_Pediculus melittae_," that was believed by Kirby to be a sort of bee-louse. Some species of the genus _Meloe_ are still common in Britain, and the Insects may be seen with heavy distended abdomen grazing on herbage in the spring. The females are enormously prolific, a single one producing, it is believed, about 10,000 eggs. _Meloe_ is also dependent on _Anthophora_, and its life-history seems on the whole to be similar to that of _Sitaris_; the eggs are, however, not necessarily deposited in the neighbourhood of the bees' nests, and the triungulins distribute themselves on all sorts of unsuitable Insects, so that it is possible that not more than one in a thousand succeeds in getting access to the _Anthophora_ nest. It would be supposed that it would be a much better course for these bee-frequenting triungulins to act like those of _Epicauta_, and hunt for the prey they are to live on; but it must be remembered that they cannot live on honey; the one tiny egg is their object, and this apparently can only be reached by the method indicated by Fabre. The history of these Insects certainly forms a most remarkably instructive chapter in the department of animal instinct, and it is a matter for surprise that it should not yet have attracted the attention of comparative psychologists. The series of actions, to be performed once and once only in a lifetime by an uninstructed, inexperienced atom, is such that we should _a priori_ have denounced it as an impossible means of existence, were it not shown that it is constantly successful. It is no wonder that the female _Meloe_ produces 5000 times more eggs than are necessary to continue the species without diminution in the number of its individuals, for the first and most important act in the complex series of this life-history is accomplished by an extremely indiscriminating instinct; the {275}newly hatched _Meloe_ has to get on to the body of the female of one species of bee; but it has no discrimination whatever of the kind of object it requires, and as a matter of fact, passes with surprising rapidity on to any hairy object that touches it; hence an enormous majority of the young are wasted by getting on to all sorts of other Insects; these larvae have been found in numbers on hairy Coleoptera as well as on flies and bees of wrong kinds; the writer has ascertained by experiment that a camel's-hair brush is as eagerly seized, and passed on to, by the young _Meloe_ as a living Insect is.

The histories of several other Cantharids have been more or less completely discovered. Fabre has found the larva of _Cerocoma schaefferi_ attacking the stores of provisions laid up by a fossorial wasp of the genus _Tachytes_, and consisting of Orthoptera of the family Mantidae. The student who wishes for further information may refer to M. Beauregard's work on this family.[144]

Some half-dozen species of the genus _Cephaloon_ found in Siberia, Japan, and North America, have, by some authorities, been separated as the family Cephaloidae. Nothing is known as to the metamorphosis of these rare beetles; and at present it is not necessary to distinguish them from Cantharidæ.

FAM. 76. TRICTENOTOMIDAE.—_Large Heteromera, with powerful free projecting mandibles; the antennae long, but with the terminal three joints short, with angular projections on one side._ This family includes only two genera and seven or eight species. They are very remarkable Insects; _Autocrates aenea_ being three inches long. The family is of considerable interest, as it seems to have no affinity with any other Coleoptera. The appearance of the species somewhat reminds one of Lucanidae, or Prionides; but Trictenotomidae have even less relation to those beetles than they have to the members of the Heteromerous series. The Trictenotomidae appear to be found only in the primitive forests of the Indian and Indo-Malayan regions. Nothing is known as to their life-histories.

{276}SERIES V. PHYTOPHAGA.

_Tarsi apparently four-jointed, the three basal joints usually densely
set with cushion-like pubescence beneath; the third joint different in
form, being divided into two lobes, or grooved on its upper surface so as
to allow of the fourth joint being inserted near its base instead of at
its extremity. Head not forming a definite prolonged beak; its labrum
visible, the palpi rarely (and even then not completely) occluded in the
mouth._

This great series of beetles includes something like 35,000 species. It approaches, like all the other series, the Polymorpha, especially the family Erotylidae placed therein, but in the great majority of cases there is no difficulty in recognising its members. The tarsi have never the Heteromerous formula, the head is not constructed like that of Rhynchophora, nor the mouth and feet like those of Adephaga; the antennae are different from those of the Lamellicorns. The tarsi are really five-jointed, for careful inspection shows that the long claw-joint has at its extreme base a small nodule, which is undoubtedly the fourth joint (Fig. 142, B). In speaking of the joints it is, however, customary not to refer to this small and functionally useless joint at all, and to call the claw-joint the fourth; when the little joint is referred to it may be called the true fourth joint.

Nearly the whole of the enormous number of species of this series are directly dependent on the vegetable kingdom for their nutriment; they are therefore well styled Phytophaga. This term is, however, restricted by some systematists to the family we have called Chrysomelidae. Although there is enormous variety in this series, three families only can be at all naturally distinguished, and this with difficulty. Of these the Bruchidae are seed-feeders, the Chrysomelidae, as a rule, leaf-feeders, the Cerambycidae wood and stem-feeders. The number of exceptions to this rule is but small, though certain Cerambycidae and certain Chrysomelidae live on roots.

FAM. 77. BRUCHIDAE.—_Prosternum extremely short; in front perpendicular; behind the coxae, forming merely a transverse lamina with pointed extremity. Hind femora more or less {277}thickened._ This comparatively small family includes about 700 species of small, unattractive beetles. The larvae live in seeds; hence some of the species are liable to be transported by means of commerce; some of them do considerable injury; peas and beans being specially subject to their attacks. They are able to complete their growth with a very small amount of nutriment, some of them consuming only a portion a little larger than themselves of a bean or pea. The larvae are fat maggots without legs, but Riley has discovered that the young larvae of _Bruchus pisi_ and _B. fabae_ have, when first hatched, three pairs of legs which are subsequently lost. They also have peculiar spinous processes on the pronotum. Both of these characteristics may be correlative with the transient differences in the activities of the larva, for the little creature is not at first located in the pea, but mines a gallery in the pod, in which it moves about, subsequently entering the pea and losing its legs. There is a good deal of difference in these respects between the two species—_B. pisi_ and _B. fabae_—examined by Riley, and as but little is known of the life-histories of other Bruchidae it is probable that still greater variety prevails. Heeger has found that _Bruchus lentis_ sometimes requires two seeds to enable it to complete its growth; it is, notwithstanding its legless state when half-grown, able to migrate by dropping to the earth, and dragging itself along by its mandibles till it comes to another pod into which it bites its way.

The family has, until recently, been placed in the {278}Rhynchophorous series, with which it has, however, no direct connection. On the other hand, it is so closely connected with Chrysomelidae that it is not possible to indicate good characters to distinguish the two at present. The Australian genus _Carpophagus_, and the large South American species of _Caryoborus_ appear to be quite indistinguishable as families, though Lacordaire and Chapuis placed one in Bruchidae, the other in Chrysomelidae. The definition we have given applies, therefore, to the majority of the family, but not to the aberrant forms just mentioned. The European genus _Urodon_ appears to belong to Anthribidae, not to Bruchidae. The family Bruchidae is called Mylabridae by some.

FAM. 78. CHRYSOMELIDAE.—_Antennae moderately long; eyes moderately large, usually not at all surrounding the insertion of the antennae; upper surface usually bare, frequently brightly coloured and shining._ This enormous family comprises about 18,000 species of beetles, in which the form and details of structure are very varied. No satisfactory character for distinguishing Chrysomelidae from Cerambycidae has yet been discovered, although the two families are certainly distinct and natural. Most of the Chrysomelidae live on foliage; few of them are more than half an inch long, whereas the Cerambycidae are wood-feeders and usually of more elongate form and larger size. The potato beetle, or Colorado beetle, that occasioned so much destruction in North America some thirty years ago, and the introduction of which into Europe was anticipated with much dread, is a good example of the Chrysomelidae. The turnip flea, a tiny hopping beetle, is among the smallest forms of the family, and is a member of another very extensive subdivision of Chrysomelidae, viz. Halticides. The term Phytophaga is by many naturalists limited to Chrysomelidae, the Cerambycidae being excluded. The classification of the family is but little advanced, but the enormous number of species of Chrysomelidae are placed in four divisions, viz.:—

{279}Prothorax much narrower at the base than the elytra, and usually
without side-margins (raised edges). Sub-fam. 1. Eupoda; with three
divisions, Sagrides, Donaciides, Criocerides.

The basal ventral plates of the abdominal segments are somewhat shorter
in the middle than at the sides, the fourth one being often invisible in
the middle, while the fifth is very large. Sub-fam. 2. Camptosomes; with
six divisions, Megascelides, Megalopides, Clythrides, Cryptocephalides,
Chlamydes, Sphaerocarides.

In the other two groups there is no great disparity between the fourth
and fifth ventral plates.

Prothorax not greatly narrower at the base than the elytra, and usually
with distinct edges at the outsides. Sub-fam. 3. Cyclica; with four
divisions, Lamprosomides, Eumolpides, Chrysomelides, Galerucides.

Front of the head bent downwards or inflexed, so that the mouth is on the
lower aspect. Antennae inserted close together on the most anterior part
of the head, so that they are more forward than the mouth. Sub-fam. 4.
Cryptostomes; with two divisions Hispides, Cassidides.

In the other three divisions the mouth is placed as usual, but the insertion of the antennae varies a good deal.

The larvae of about 100 species of the family are known; they are arranged in accordance with their habits, by Chapuis,[145] in six groups, viz.:

1. Elongate larvae, living under water, and there undergoing their
metamorphosis. (Donaciides.)

2. Larvae mining in leaves, and undergoing their metamorphosis in the
leaf. (Hispides and some Halticides.)

3. Short convex larvae, frequently with leathery and pigmented
integuments, living exposed on plants. (Most of the Cyclica.)

4. Larvae of short form; covering the body with excrementitious matter.
(Some Criocerides.)

5. Peculiar larvae of short form, spiny, and protecting their bodies by
excrementitious matter attached by a special apparatus, the excrement
itself being modified so as to be suitable for retention. (Cassidides.)

6. Elongate, pallid, larvae with curved abdomen; living in shell-like
cases, and undergoing metamorphosis therein. (Most of the Camptosomes,
the habits of which are known.)

Though our knowledge of these larvae extends to only about 100 out of 18,000 species, the above category by no means includes all the kinds of larvae; Captain Xambeu having recently discovered that the larva of _Chrysochus pretiosus_ lives in the earth feeding on roots after the manner of a _Rhizotrogus_ larva, which it resembles. The larva of _Sagra splendida_ lives {280}inside the stems of _Dioscorea batatas_, in swellings; the group Sagrides, to which it belongs, is a very anomalous one.

i. Eupoda. The beetles of the genus _Donacia_ are of special interest. They form, with the genus _Haemonia_, a peculiar group, well represented in Europe, and also in our own country. They are all connected with aquatic plants, the species of _Haemonia_ living entirely under water, while the _Donacia_ live in the imago-state an aërial life, though many of them enter the water with great readiness, and, it is said, are able to take wing from the surface. The larvae live on the roots of aquatic plants, and derive not only nutriment but air therefrom; they pass several months as pupae (or as resting larvae waiting for pupation), under water in cocoons which they construct, and which, incredible as it may seem, are filled with air, not water. Exact details as to the construction of these cocoons are wanting. It was formerly absurdly supposed that the larva swelled itself out to the size of the cocoon it was about to make, and so served as a mould, subsequently contracting. The observations of Schmidt-Schwedt[146] make it, however, more probable that the plant itself furnishes the air which, under pressure of the water (so he supposes), fills the cocoon; the larva wounds the root, piercing to an air-vessel and then constructs the cocoon on this spot, leaving to the last moment an orifice, according to Schmidt, as an exit for the water. The larva uses a similar artifice for obtaining air; it has no gills, but is provided near the extremity of the body with two sharp chitinous processes which it drives into the root of the plant till it penetrates an air-vessel. Schmidt thinks the processes serve as conduits to conduct the air to the tracheae, but Dewitz thinks the air enters the larva in a more normal manner, by means of a stigma placed at the base of the piercing process. A similar larva exists in _Haemonia_; which genus is additionally interesting from the fact that the imago lives entirely submerged. It is not known how it breathes. This genus is the only member of the Chrysomelidae that does not possess the structure of the feet that is characteristic of the Phytophaga. The late Professor Babington about sixty years ago found _H. curtisi_ at Cley on the Norfolk coast on submerged _Potamogeton pectinatus_, but it has not been met with there for a great many years.

The larvae of Criocerides are of two kinds, in one of which the {281}body is peculiarly shaped in conformity with the curious habit of using the excrement as a covering. The larva is less elongate than usual, and has the anus placed on the upper surface, and formed so that the excrement when voided is pushed forward on to the Insect; here it is retained by means of a slimy matter, and a thick coat entirely covering the creature, is ultimately formed. The larva of _Lema melanopa_ is not uncommon about Cambridge, where it feeds on the leaves of growing corn. It is a remarkable fact that even in one genus the species have some of them this habit, but others not. The species of _Crioceris_ living on lilies—_C. merdigera_, _e.g._—are noted for possessing it; while _C. asparagi_ does not protect itself in this way, but emits fluid from its mouth when disturbed. This larva is a serious nuisance in some localities to the cultivators of asparagus. The eggs are deposited on the stems of the plant—as shown in our figure—sometimes in great numbers.

The perfect Insects of many of the Criocerides possess a stridulating organ. Two contiguous areas at the base of the last dorsal segment, where they can be rubbed by the tips of the elytra, are slightly elevated and bear very close and fine straight lines.

ii. The Camptosomes, as we have already noticed, are distinguished by a peculiar structure of the abdomen. This character appears to be connected with a very remarkable habit, viz. the formation of a case to envelop the egg. The tip of the abdomen is somewhat curved downwards, and, in the female, bears a hollow near the extremity; when an egg is extruded the female holds it in this hollow by means of the hind legs, and envelops it with a covering said to be excrementitious. When the larva hatches, it remains within this case, and {282}subsequently enlarges it by additions from its own body. The beautiful Insects of the genus _Cryptocephalus_, which is fairly well represented in Britain, belong to this division. The exotic group Megalopodes is incorrectly placed in Camptosomes; the side pieces of the prothorax meet in it behind the middle coxae, as they do in Rhynchophora. The species of Megalopodes stridulate by means of an area on the base of the meso-scutellum rubbed by a ridge inside the pronotum, as in the Cerambycidæ.

iii. The division Cyclica includes the great majority of Chryomelidae; we have not less than 170 species in Britain. The larvae live, like those of Lepidoptera, at the expense of foliage, and the species frequently multiply to such an extent as to be injurious. Some of them are destroyed in great numbers by Hymenopterous parasites, the Braconid genus _Perilitus_ being one of the best known of these; in some cases the parasite deposits its eggs in either the larva or perfect Insect of the beetle, and the metamorphoses of the parasites in the latter case are sometimes, if not usually, completed, the larvae emerging from the living beetles for pupation.

iv. The Cryptostomes, though comparatively few in number of species, include some very remarkable beetles. There are two groups, Hispides and Cassidides. The former are almost peculiar to the tropics and are not represented by any species in the British fauna. The head in this group is not concealed; but in the Cassidides the margins of the upper surface are more or less expanded, so that the head is usually completely hidden by the expansion of the pronotum. Both the groups are characterised by the antennae being inserted very near together, and by the short claw-joint of the feet. _Hispa_ is one of the most extensive of the numerous genera of Hispides, and is remarkable from the imago being covered on the surface with long, sharp spines. But little is known as to the metamorphosis, beyond the fact already alluded to, that the larvae of several species mine the interior of leaves. The larva of _Hispa testacea_, according to Perris,[147] makes use of the leaves of _Cistus salvifolius_ in Southern Europe; it is broad and flat, and possessed of six short legs. The eggs are not deposited by the parents inside the leaves, but are probably attached to various parts of the plant. After hatching, the young larva enters a leaf, and feeds on the parenchyma without rupturing {283}the epidermis; but when it has consumed about three-fourths of the soft interior of the leaf it ruptures the epidermis of the upper surface, and seeks another leaf; this found, it places itself on the midrib, tears the upper epidermis, and lodges itself in the leaf. In the case of this second leaf it attacks the parenchyma in the neighbourhood of the petiole, and so forms an irregular tube which has an open mouth, the point of entry. In this tube it undergoes its metamorphosis. Each larva, it is said, always makes use of two leaves, and of two opposed leaves. A knowledge of the habits of some of the larger of the exotic Hispides would be of much interest.

The Cassidides, in addition to the curious marginal expansion of their upper surface, have the power of withdrawing the head into the thorax, and hence they are often called shield or tortoise-beetles. They exhibit considerable variety in form and colour, and some of them display a peculiar metallic reflection of great delicacy and beauty; this disappears entirely after death, but it may be restored by thoroughly moistening the dead Insect. The colour, therefore, probably depends on the presence of water in the integument. The larvae of Cassidides are notorious on account of their habit of covering their bodies with dried excrement, for which purpose they are provided with a forked {284}process at the posterior extremity; this serves to place the protecting matter in a proper position and to retain it there. The excrement assumes in various species forms so peculiar that they cannot be considered merely incidental. In several species this covering-matter is like lichen. This is the case with _Dolichotoma palmarum_, the larva of which has, in place of the usual fork, a more complex appendage on the back for the purpose of preparing and retaining its peculiar costume. The pupae, too, sometimes retain the larval skin. An extremely remarkable pupa of a Cassidid—possibly of the genus _Aspidomorpha_—was recently found by Dr. Arthur Willey in New Britain (Fig. 144). The back of the pupa is covered with a complex appendage, so that the creature has no resemblance to an Insect; this appendage is perhaps capable of being moved, or even extended (Fig. 144, A), during life. Whether it may be formed by the retention of portions of the moulted skins of the larva we cannot say with certainty.

The most remarkable of the Cassidid coverings yet discovered are those formed by certain small beetles of the tropical American genus _Porphyraspis_. _P. tristis_ is apparently a common Insect at Bahia, where it lives on a cocoa-palm. The larva is short and broad, and completely covers itself with a very dense coat of fibres, each many times the length of the body, and elaborately curved so as to form a round nest under which the larva lives. On examination it is found that these long threads are all attached to the anal extremity of the Insect, and there seems no alternative to believing that each thread is formed by small pieces of fibre that have passed through the alimentary canal, and are subsequently stuck together, end to end. The process of forming these long fibres, each one from scores of pieces of excrement, and giving them the appropriate curve, is truly remarkable. The fibres nearest to the body of the larva are abruptly curled so as to fit exactly, and make an even surface; but the outside fibres stand out in a somewhat bushy fashion. The construction is much like that of a tiny bird's nest. Señor Lacerda informed the writer that the larva makes a nest as soon as it is hatched. Another _Porphyraspis_—_P. palmarum_—has been recorded as {285}forming similar nests on a species of _Thrinax_ in St. Domingo. Candèze says[148] that when it has completed its growth the larva ejects on to the leaf a quantity of semi-liquid matter, and this, on drying, sticks the nest to the leaf, so that the metamorphosis is effected under shelter.

FAM. 79. CERAMBYCIDAE (_Longicorns_).—_Form usually oblong, not much curved in outline at the sides; surface very frequently rendered dull by a very minute hairiness, which often forms a pattern; antennae usually long, and their insertion much embraced by the eyes._ This great family of beetles includes some 12,000 or 13,000 known species. The elegance and variety of their forms and the charm of their colours have caused them to attract much attention, so that it is probable that a larger proportion of the existing species have been obtained than is the case in any other of the great families of Coleoptera. Still it is not likely that one-half of the living forms are known. It is not possible at present to point out any one character of importance to distinguish Cerambycidae from Chrysomelidae, though the members of the two families have, as a rule, but little resemblance in external appearance. Most of them live on, or in, wood, though many are nourished in the stems of herbaceous plants. The larvae live a life of concealment, and are soft, whitish grubs with powerful mandibles, and usually with a comparatively small head, which is not much exserted from the thorax. Most of them are without legs, but a good many have three pairs of small legs, and there are numerous cases in which the surface of the body is furnished above or below with swellings believed to act as pseudopods (Fig. 84), and help the larvae to move about in their galleries; but this is probably not the sole function of these organs, as their surface is varied in character, and often not of a kind that appears specially adapted to assist in locomotion. There is a slight general resemblance between the larvae of Cerambycidae and those of Buprestidae, and when the thorax of a Longicorn larva is unusually broad, _e.g._ _Astynomus_, this similarity is very pronounced.

{286}The modes of life of Cerambycid larvae exhibit considerable variety, and much perfection of instinct is displayed by the larvae, as well as by the mother beetles. The larvae of _Saperda populnea_, are common in certain woods in the South of England in the stems of aspen; they consume only a small quantity of the interior of the stem, and are probably nourished by an afflux of sap to the spot where they are situated. _Elaphidion villosum_ is called the oak-pruner in North America. The parent beetle lays an egg near the axilla of a leaf-stalk or small stem, and the young larva enters this and feeds on the tender material; as it grows it enters a larger limb, and makes an incision within this in such a manner that the wood falls to the ground with the larva within it, the dead wood serving subsequently as pabulum and as a shelter, within which the metamorphosis is completed. The species of the American genus _Oncideres_ are called girdlers, because the parent beetle, after laying an egg in a small branch, girdles this round with a deep incision, so that the portion containing the larva sooner or later falls to the ground. The growth of a Longicorn larva frequently takes more than a year, and under certain circumstances it may be enormously prolonged. _Monohammus confusus_ has been known to issue from wooden furniture in a dwelling-house when the furniture was fifteen years old. Individuals of another Longicorn have issued from the wood of a table, twenty and even twenty-eight years after the felling of the tree from which the furniture was made. Sereno Watson has related a case from which it appears probable that the life of a Longicorn beetle extended over at least forty-five years.[149] It is generally assumed that the prolongation of life in these cases is due to the beetle resting quiescent for long after it has completed the metamorphosis. Recent knowledge, however, renders it more probable that it is the larval life that is prolonged; the larva continuing to feed, but gaining little or no nutriment from the dry wood in these unnatural conditions. Mr. C. O. Waterhouse had for some years a Longicorn larva under observation, feeding in this way in the wood of a boot-tree;[150] the burrows in the wood contained a great deal of minute dust indicating that the larva passed much matter through the alimentary canal, probably with little result in the way of nutriment.

{287}There are numerous Longicorns that bear a great resemblance in form and colour to Insects to which they are not related. Haensch[151] has noticed that species of the genus _Odontocera_ resemble various Hymenoptera, one species being called _O. braconoides_; he also observed that these Hymenoptera-like Longicorns, instead of withdrawing their underwings under the elytra as beetles generally do, vibrate them rapidly like Hymenoptera. A large number of Longicorns stridulate loudly by rubbing a ridge inside the pronotum on a highly specialised, striate surface at the base of the scutellum, and therefore covered up when the Insect is contracted in repose. A few produce noise by rubbing the hind femora against the edges of the elytra, somewhat after the fashion of grasshoppers. In this case there appears to be comparatively little speciality of structure, the femora bearing, however, more or less distinct small granules. The species of the Hawaiian genus _Plagithmysus_ produce sound in both these manners, the thoracic stridulating organ being beautifully developed, while in some species the margin of the elytra and base of the femora are also well adapted for the purpose of sound-production, and in a few species of the genus there are also highly-developed stridulating surfaces on the hind and middle coxae. This is the only case in which a beetle is known to possess more than one set of sound-organs in the imago state.

Three divisions of this family are distinguished, viz.—

1. Front coxae large and transverse; prothorax with distinct side
margins. Sub-fam. 1. Prionides.

2. Front coxae not greatly extended transversely, thorax not margined;
last joint of maxillary palpus not pointed, usually broader (more or
less) than the preceding joint. Sub-fam. 2. Cerambycides.

3. Front coxae usually round and deeply embedded; last joint of maxillary
palpus pointed; front tibiae with a more or less distinct, slanting
groove on the inner side. Sub-fam. 3. Lamiides.

The Prionides are on the average considerably larger in size than the members of the other divisions, and they include some of the largest of Insects. The Amazonian _Titanus giganteus_ and the Fijian _Macrotoma heros_ are amongst the most gigantic. Some of the Prionides have a great development of the mandibles in the male sex analogous to that we have already noticed in Lucanidae. The larvae of the large Prionides appear in various parts of the world to have been a favourite food with native {288}tribes, and Lumholz states that they are really good eating. In consequence of the destruction of forests that has progressed so largely of late years these gigantic Prionides have become much rarer.

Several aberrant forms are included in Prionides. The genus _Parandra_ has five-jointed tarsi; the third joint being much smaller than usual, so that the fourth joint is not concealed by it. The Brazilian _Hypocephalus armatus_ was for long a subject of dispute as to its natural position, and was placed by different authorities in widely-separated families of Coleoptera. The structure of this aberrant Longicorn seems to be only explicable on the hypothesis of warfare amongst the males.[152] Nothing is, however, known as to the habits and history of the Insect, and only one or two specimens of the female have yet been obtained.

The family Spondylidae has been proposed for some of these aberrant Longicorns, but as it includes but very few, and highly discrepant, species, it is neither natural nor of much use for systematic purposes.

The Lamiides are the most highly specialised division of the Longicorns, and includes the larger number of the species. The front of the head is usually placed at right angles to the vertex, and in some cases (groups Hippopsini, Spalacopsini) it is strongly inflexed, so that the mouth is placed on the under side of the head. The extension of the eyes round the antennae is accompanied by very curious shapes of those organs, and not infrequently each eye is divided into two more or less widely-separated parts, so that the Insect has, on the external surface, four eyes.

SERIES VI. RHYNCHOPHORA.

_Head more or less prolonged in front to form a snout or beak, called
rostrum. Tarsi four-jointed, usually at least the third joint broad and
densely pubescent beneath._

This enormous series includes about 25,000 species, and as may well be imagined shows a great variety of structure amongst its forms. The vast majority may, however, be readily recognised by the two characters mentioned above. There are some cases in which the beak is indistinct, and others in which the tarsi are {289}five-jointed (_Dryophthorus_), and even slender (Platypides). In these cases a close examination shows that the gular region on the middle of the back of the under surface of the head cannot be detected, and that the back of the prosternum is very strongly consolidated by the side-pieces of the thorax meeting together and being very firmly joined behind the coxae. The beak is in the great majority perfectly distinct, though it varies so extremely in form that it can only be briefly described by saying that it is a prolongation of the head in front of the eyes, or that the antennae are inserted on its sides near to, or far from, the tip. It has been ascertained in many cases that the rostrum is used by the female to assist in placing the eggs in suitable places, a hole being bored with it; in some cases it is also used to push the egg far into the hole in which it has previously been placed by the ovipositor; but there are many forms in which it is fairly certain that it is not so used. What purpose it serves in the male is totally unknown. In many members of the series, the rostrum differs in form in the two sexes, and in most, if not in all, these cases it is clear that the distinctions tend in the direction of making the beak of the female more efficient for the mechanical purpose we have mentioned.

It was proposed by Leconte and Horn to separate this series from all the other Coleoptera as a primary division, and they looked on it as of lower or more imperfect structure. Packard has very properly protested against this interpretation; and there seems to be no reason whatever for considering the Rhynchophora as "lower" than other beetles; indeed we should be inclined to place such forms as Calandrides {290}amongst the most perfect of Insects; their external structure (as shown by _Eugnoristus monachus_, Fig. 147) being truly admirable.

Only four families of Rhynchophora can be at present accepted as satisfactory; one of these—Curculionidae—includes an enormous majority of the whole series. Though it is probable that it will ultimately be divided into several families, the attempts to that end that have already been made are not satisfactory.

FAM. 80. ANTHRIBIDAE.—_Palpi usually not covered, but distinct and flexible. Antennae often long, not elbowed, the first joint not very long. Third joint of tarsus small, usually much concealed by being embraced by the second joint. Pygidium exposed; propygidium deeply grooved in the middle._ This family includes 800 or more species, which are mostly tropical; it is very sparsely represented in the faunas of Europe and North America. It is quite distinct from Curculionidae with which it was formerly associated. It contains many graceful Insects having a certain resemblance with Longicorns on account of the large development of the antennae. The habits and metamorphoses are but little known. It seems probable that many species find their nutriment in old wood or boleti The larvae of some genera (_Cratoparis_ and _Araeocerus_) have legs, but in others the legs are wanting, and the larvae are said to completely resemble those of Curculionidae. In the larva of our tiny British species, _Choragus sheppardi_, the legs are replaced by three pairs of thoracic, sac-like pseudopods. This Insect makes burrows in dead branches of hawthorn. The larvae of the genus _Brachytarsus_ have been ascertained to prey on Coccidae.

FAM. 81. CURCULIONIDAE (Weevils).—_The beak of very variable length and thickness; the palpi small, nearly always concealed within the mouth, short, and rigid. Labrum absent. Antennae of the majority elbowed,_ i.e. _with the basal joint longer, and so formed that when it is laterally extended the other joints can be placed in a forward direction._ This enormous family includes {291}about 20,000 known species, and yet a large portion of the species yearly brought from the tropics still prove to be new. The rostrum or beak exhibits excessive variety in form, and is in many cases different in the sexes; in this case it is usually longer and thinner in the female. As the rostrum is one of the chief characters by which a member of the family may be recognised, it is necessary to inform the student that in certain forms (the Australian Amycterides, _e.g._) the organ in question may be so short and thick that it is almost absent. In these cases the Insect may be identified as a Curculionid by the gular area being absent on the under side of the head, and by the concealment of the palpi. The tarsi are usually of the same nature as those of Phytophaga, already described, but the true fourth joint is less visible. In the Brachycerides this joint is not present, and the third joint is not lobed. The palpi are flexible and more or less exserted in a very few species (Rhynchitides); in Rhinomacerides there is also present a minute labrum. The front coxae are deeply embedded, and in many forms the prosternum is peculiar in structure; the side-pieces (epimera) meeting at the back of the prosternum in the middle line. This, however, is not universal in the family, and it occurs in some other beetles (_e.g._, Megalopodides of the Phytophaga). The larvae are without legs. They are vegetarian, the eggs being deposited by the mother-beetle in the midst of the food. These larvae may be distinguished from those of Longicorns by the general form, which is sub-cylindric or rather convex, not flattened, and more particularly by the free, exserted head, the mouth being directed downwards; the attitude is generally a curve, and the anterior part of the body is a little the thicker. No part of plants is exempt from the attacks of the larvae of Curculionidae; buds, twigs, leaves, flowers, fruits, bark, pith, roots and galls may each be the special food of some Curculionid. Certain species of the sub-families Rhynchitides and Attelabides prepare leaves in an elaborate manner to serve as food and dwelling for their young. If young birches, or birch bushes from 5 to 10 feet in height, be looked at in the summer, one may often notice that some of the leaves are rolled so as to form, each one, a little funnel. This is the work of _Rhynchites_ (or _Deporaus_) _betulae_, a little Curculionid beetle (Fig. 149). An inspection of one of these funnels will show that it is very skilfully constructed.

{292}

The whole of a leaf is not used in the formation of a funnel, cuts being made across the leaf in suitable directions. The beetle standing on a leaf, as shown in the figure, proceeds to cut with its mandibles an incision shaped like an erect S, commencing at a certain part of the circumference, and ending at the midrib of the leaf; the beetle then goes to the other side of the midrib, and continues its incision so as to form another S-like curve considerably different from the first; being prostrate and less abrupt. Thus the blade of the leaf is divided into two halves by certain curved incisions, the midrib remaining intact. The little funnel-twister now commences to roll up the leaf to form the funnel; and this part of the work is greatly facilitated by the shape of the incisions. Going back to the spot where it commenced work, by the aid of its legs it rolls one side of the leaf round an ideal axis, somewhat on the same plan as that adopted by a grocer in forming a paper-funnel for sugar. The incisions are found to be just of the right shape to make the overlaps in the rolling, and to retain them rolled-up with the least tendency to spring back. After some other operations destined to facilitate subsequent parts of its task, the beetle enters the rolled-up part of the leaf and brings it more perfectly together; it again comes out and, pursuing a different system, holds on with the legs of one side of the body {293}to the roll, and with the other legs drags to it the portion of the leaf on the other side of the midrib so as to wrap this part (_i.e._ the result of its second incision) round the part of the funnel already constructed. This being done the Insect again enters the funnel, bites three or four small cavities on the inside of the leafy wall and deposits an egg in each. Afterwards it emerges and fits the overlaps together in a more perfect manner so as to somewhat contract the funnel and make it firmer; then proceeding to the tip, this is operated on by another series of engineering processes and made to close the orifice; this part of the operation being analogous to the closing by the grocer of his paper-funnel after the sugar has been put in. The operation of the beetle is, however, much more complex, for it actually makes a sort of second small funnel of the tip of the leaf, bends this in, and retains it by tucking in some little projections. The work, which has probably lasted about an hour, being now completed, the creature takes a longer or shorter rest before commencing another funnel. We have given only a sketch of the chief points of the work, omitting reference to smaller artifices of the craft master; but we may remark that the curved incisions made by the beetle have been examined by mathematicians and duly extolled as being conducted on highly satisfactory mathematical principles. It is impossible at present for us to form any conception as to the beetle's conceptions in carrying out this complex set of operations. Our perplexity is increased if we recollect its life-history, for we then see that neither precept or example can have initiated its proceedings, and that imitation is out of the question. The eggs hatch in their dark place, giving rise to an eyeless maggot, which ultimately leaves the funnel for the earth. The parts of this maggot subsequently undergo complete change to produce the motionless pupa of entirely different form, from which emerges the perfect Insect. Hence the beetle cannot be considered to have ever seen a funnel, and certainly has never witnessed the construction of one, though, when disclosed, it almost immediately sets to work to make funnels on the complex and perfect system we have so imperfectly described. More general considerations only add to the perplexity we must feel when reflecting on this subject. Why does the Insect construct the funnel at all? As a matter of protection it appears to be of little use, for the larvae are known to suffer from the attacks {294}of parasites as other Insects do. We have not the least reason for supposing that this mode of life for a larva is, so far as utility is concerned, better than a more simple and usual one. Indeed, extraordinary as this may appear, it is well known that other species of the same genus adopt a simple mode of life, laying their eggs in young fruits or buds. We think it possible, however, that a knowledge of the mode of feeding of this larva may show that a more perfect nutrition is obtained from a well-constructed cylinder, and if so this would to a slight extent satisfy our longing for explanation, though throwing no light whatever on the physiology or psychology of the artificer, and leaving us hopelessly perplexed as to why a beetle in ages long gone by should or could adopt a mode of life that by long processes of evolution should, after enormous difficulties have been overcome, attain the perfection we admire.[153]