Chapter VIII: Hemiptera, or Bugs—anoplura 532 (10)

The larvae of the aquatic division of the family have been to a certain extent studied by Schiödte and others; those of the Sphaeridiides—the terrestrial group of the family—are but little known. All the larvae seem to be predaceous and carnivorous, even when the imago is of vegetable-feeding habits; and Duméril states that in _Hydrous caraboides_ the alimentary canal undergoes a great change at the period of metamorphosis, becoming very elongate in the adult, though in the larva it was short. The legs are never so well developed as they are in the Adephaga, the tarsi being merely claw-like or altogether wanting; the mandibles are never suctorial. The respiratory arrangements show much diversity. In most of the Hydrophilides the process is carried on by a pair of terminal spiracles on the eighth abdominal segment, as in Dytiscidae, and these are either exposed or placed in a respiratory chamber. In _Berosus_ the terminal stigmata are obsolete, and the sides of the body bear long branchial filaments. Cussac says that in _Spercheus_ (Fig. 101) there are seven pairs of abdominal spiracles, and that the larva breathes by presenting these to the air;[98] but Schiödte states that in this form there are neither thoracic nor abdominal spiracles, except a pair placed in a respiratory chamber on the eighth segment of the abdomen, after the manner described by Miall as existing in _Hydrobius_. No doubt Cussac was wrong in supposing the peculiar lateral abdominal processes to be {219}stigmatiferous. In _Berosus_ there are patches of aëriferous, minute pubescence on the body. The pupae of Hydrophilides repose on the dorsal surface, which is protected by spinous processes on the pronotum, and on the sides of the abdomen.

We have already remarked that this is one of the most neglected of the families of Coleoptera, and its classification is not satisfactory. It is usually divided into Hydrophilides and Sphaeridiides. The Sphaeridiides are in large part terrestrial, but their separation from the purely aquatic Hydrophilides cannot be maintained on any grounds yet pointed out. Altogether about 1000 species of Hydrophilidae are known, but this probably is not a tenth part of those existing. In Britain we have nearly ninety species. Some taxonomists treat the family as a series with the name Palpicornia. The series Philhydrida of older authors included these Insects and the Parnidae and Heteroceridae.

FAM. 13. PLATYPSYLLIDAE.—This consists of a single species. It will be readily recognised from Fig. 102, attention being given to the peculiar antennae, and to the fact that the mentum is trilobed behind. This curious species has been found only on the beaver. It was first found by Ritsema on American beavers (_Castor canadensis_) in the Zoological Gardens at Amsterdam, but it has since been found on wild beavers in the Rhone in France; in America it appears to be commonly distributed on these animals from Alaska to Texas. It is very remarkable that a wingless parasite of this kind should be found in both hemispheres. The Insect was considered by Westwood to be a separate Order called Achreioptera, but there can be no doubt that it is a beetle. It is also admitted that it shows some points of resemblance with Mallophaga, the habits of which are similar. Its Coleopterous nature is confirmed by the larva, which has been described by both Horn and Riley.[99] Little is known as to the food and life-history. Horn states that the eggs are placed on {220}the skin of the beaver amongst the densest hair; the larvae move with a sinuous motion, like those of Staphylinidae. It has been suggested that the Insect feeds on an Acarid, _Schizocarpus mingaudi_; others have supposed that it eats scales of epithelium or hairs of the beaver.

FAM. 14. LEPTINIDAE.—_Antennae rather long, eleven-jointed, without club, but a little thicker at the extremity. Eyes absent or imperfect. Tarsi five-jointed. Elytra quite covering abdomen. Mentum with the posterior angles spinously prolonged._ A family of only two genera and two species. Their natural history is obscure, but is apparently of an anomalous nature; the inference that may be drawn from the little that is known being that they are parasitic on mammals. There is little or nothing in their structure to indicate this, except the condition of blindness; and until recently the Insects were classified amongst Silphidae. _Leptinus testaceus_ (Fig. 103) is a British Insect, and besides occurring in Europe is well known in North America. In Europe it has been found {221}in curious places, including the nests of mice and bumble-bees. In America it has been found on the mice themselves by Dr. Ryder, and by Riley in the nests of a common field-mouse, together with its larva, which, however, has not been described. The allied genus _Leptinillus_ is said by Riley to live on the beaver, in company with _Platypsyllus_.[100] It has been suggested that the natural home of the _Leptinus_ is the bee's nest, and that perhaps the beetle merely makes use of the mouse as a means of getting from one nest of a bumble-bee to another.

FAM. 15. SILPHIDAE.—_The mentum is usually a transverse plate, having in front a membranous hypoglottis, which bears the exposed labial palpi, and immediately behind them the so-called bilobed ligula. The anterior coxae are conical and contiguous: prothoracic epimera and episterna not distinct. Visible abdominal segments usually five, but sometimes only four, or as many as seven. Tarsi frequently five-jointed, but often with one joint less. Elytra usually covering the body and free at the tips, but occasionally shorter than the body, and even truncate behind so as to expose from one to four of the dorsal plates; but there are at least three dorsal plates in a membranous condition at the base of the abdomen._ These beetles are extremely diverse in size and form, some being very minute, others upwards of an inch long, and there is also considerable range of structure. In this family are included the burying-beetles (_Necrophorus_), so well known from their habit of making excavations under the corpses of small Vertebrates, so as to bury them. Besides these and _Silpha_, the roving carrion-beetles, the family includes many other very different forms, amongst them being the larger part of the cave-beetles of Europe and North America. These belong mostly to the genera _Bathyscia_ in Europe, and _Adelops_ in North America; but of late years quite a crowd of these eyeless cave-beetles of the group Leptoderini have been discovered, so that the European catalogue now includes about 20 genera and 150 species. The species of the genus _Catopomorphus_ are found in the nests of ants of the genus _Aphaenogaster_ in the Mediterranean region. Scarcely anything is known as to the lives of either the cave-Silphidae or the myrmecophilous forms.

The larvae of several of the larger forms of Silphidae are well known, but very little has been ascertained as to the smaller forms. {222}Those of the burying-beetles have spiny plates on the back of the body, and do not resemble the other known forms of the family. The rule is that the three thoracic segments are well developed, and that ten abdominal segments are also distinct; the ninth abdominal segment bears a pair of cerci, which are sometimes elongate. Often the dorsal plates are harder and better developed than is usual in Coleopterous larvae. This is especially the case with some that are endowed with great powers of locomotion, such as _S. obscura_ (Fig. 104). The food of the larvae is as a rule decomposing animal or vegetable matter, but some are predaceous, and attack living objects. The larger _Silpha_ larvae live, like the _Necrophorus_, on decomposing animal matter, but run about to seek it; hence many specimens of some of these large larvae may sometimes be found amongst the bones of a very small dead bird. We have found the larva and imago of _S. thoracica_ in birds' nests containing dead nestlings. _S. atrata_ and _S. laevigata_ make war on snails. _S. lapponica_ enters the houses in Lapland and ravages the stores of animal provisions. _S. opaca_ departs in a very decided manner from the habits of its congeners, as it attacks beetroot and other similar crops in the growing state; it is sometimes the cause of serious loss to the growers of beet. The larvae of the group Anisotomides are believed to be chiefly subterranean in habits; that of _A. cinnamomea_ feeds on the truffle, and the beetle is known as the truffle-beetle.

The number of species of Silphidae known must be at present nearer 900 than 800. Of these an unusually large proportion belong to the European and North American regions; Silphidae being apparently far from numerous in the tropics. Rather more than 100 species are natives of Britain. The family reappears in considerable force in New Zealand, and is probably well represented {223}in South Australia and Tasmania. The most remarkable form known is perhaps the Australian genus _Ptomaphila_ (Fig. 104, B). The classification of the family is due to Dr. Horn.[101] The only change of importance that has since been suggested is the removal of _Sphaerites_ from this family to Synteliidae. Anisotomidae and Clambidae have been considered distinct families, but are now included in Silphidae.

FAM. 16. SCYDMAENIDAE.—_Minute Insects allied to Silphidae, but with the hind coxae separated, and the facets of the eyes coarser; the tarsi are five-jointed; the number of visible abdominal segments is six._ These small beetles are widely spread over the earth's surface, and about 700 species are now known, of which we have about a score in Britain; many live in ants' nests, but probably usually rather as intruders than as guests that have friendly relations with their hosts. Nothing is known as to their life-histories, but the food of the imago, so far as is known, consists of Acari. _Mastigus_ is a very aberrant form, found in moss and dead leaves in Southern Europe. By means of _Brathinus_ the family is brought very near to Silphidae; Casey, however, considers _Brathinus_ to belong to Staphylinidae rather than to Scydmaenidae. The South European _Leptomastax_ is remarkable on account of the slender, long, sickle-shaped mandibles. The Oriental genus _Clidicus_ is the largest and most remarkable form of the family; it has a very slender neck to its broad head, and is more than a quarter of an inch long.

FAM. 17. GNOSTIDAE.—_Minute Insects with three-jointed antennae, five-jointed tarsi, and three apparent ventral segments, the first of which, however, is elongate, and consists of three united plates. Elytra entirely covering the after-body._ The family consists of two species which have been found in the nests of ants, of the genus _Cremastogaster_, in Brazil.[102]

FAM. 18. PSELAPHIDAE.—_Very small Insects; the elytra much abbreviated, usually leaving as much as half the abdomen uncovered; the maxillary palpi usually greatly developed, and of a variety of remarkable forms; the segments of the abdomen not more than seven in number, with little or no power of movement. Tarsi with not more than three joints._ These small Coleoptera mostly live in the nests of ants, and present a great diversity of extraordinary {224}shapes, and very peculiar structures of the antennae and maxillary palpi. Owing to the consolidation of some of its segments, the abdomen frequently appears to have less than the usual number. In the curious sub-family Clavigerides, the antennae may have the joints reduced to two or even, to all appearance, to one; the tarsi suffer a similar reduction. There are about 2500 species of Pselaphidae known; many of them have never been found outside the ants' nests; very little, however, is known as to their natural history. It is certain that some of them excrete, from little tufts of peculiar pubescence, a substance that the ants are fond of. The secretory patches are found on very different parts of the body and appendages. _Claviger testaceus_ is fed by the ants in the same way as these social Insects feed one another; the _Claviger_ has also been seen to eat the larvae of the ants. They ride about on the backs of the ants when so inclined. The family is allied to Staphylinidae, but is easily distinguished by the rigid abdomen. Only one larva—that of _Chennium bituberculatum_—is known. It appears to be very similar to the larvae of Staphylinidae. The best account of classification and structure is that given by M. Achille Raffray,[103] who has himself discovered and described a large part of the known species.

FAM. 19. STAPHYLINIDAE.—_Elytra very short, leaving always some of the abdominal segments exposed, and covering usually only two of the segments. Abdomen usually elongate, with ten dorsal, and seven or eight ventral segments; of the latter six or seven are usually exposed; the dorsal plates as hard as the ventral, except sometimes in the case of the first two segments; the segments very mobile, so that the abdomen can be curled upwards. The number of tarsal joints very variable, often five, but frequently as few as three, and not always the same on all the feet._ Staphylinidae (formerly called Brachelytra or Microptera) is one of the most extensive of even the great families of Coleoptera; notwithstanding their diversity, they may in nearly all cases be recognised by the more than usually mobile and uncovered abdomen, combined with the fact that the parts of the mouth are of the kind we have mentioned in Silphidae. The present state of the classification of this family has been recently discussed by Ganglbauer.[104]

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At present about 9000 species are known, some of which are minute, while scarcely any attain a size of more than an inch in length, our common British black cock-tail, or "devil's coach-horse beetle," _Ocypus olens_, being amongst the largest. Though the elytra are short, the wings in many forms are as large as those of the majority of beetles; indeed many Staphylinidae are more apt at taking flight than is usual with Coleoptera; the wings when not in use are packed away under the short elytra, being transversely folded, and otherwise crumpled, in a complicated but orderly manner. It is thought that the power of curling up the abdomen is connected with the packing away of the wings after flight; but this is not the case: for though the Insect sometimes experiences a difficulty in folding the wings under the elytra after they have been expanded, yet it overcomes this difficulty by slight movements of the base of the abdomen, rather than by touching the wings with the tip. What the value of this exceptional condition of short elytra and corneous dorsal abdominal segments to the Insect may be is at present quite mysterious. The habits of the members of the family are very varied; many run with great activity; the food is very often small Insects, living or dead; a great many are found in fungi of various kinds, and perhaps eat them. It is in this family that we meet with some of the most remarkable cases of symbiosis, i.e. lives of two kinds of creatures mutually accommodated with good will. The relations between the Staphylinidae of the genera _Atemeles_ and _Lomechusa_, and certain ants, in the habitations of which they dwell, are very interesting. The beetles are never found out of the ants' nests, or at any rate not very far from them. The most friendly relations exist between them and the ants: they have patches of yellow hairs, and these {226}apparently secrete some substance with a flavour agreeable to the ants, which lick the beetles from time to time. On the other hand, the ants feed the beetles; this they do by regurgitating food, at the request of the beetle, on to their lower lip, from which it is then taken by the beetle (Fig. 82). The beetles in many of their movements exactly resemble the ants, and their mode of requesting food, by stroking the ants in certain ways, is quite ant-like. So reciprocal is the friendship that if an ant is in want of food, the _Lomechusa_ will in its turn disgorge for the benefit of its host. The young of the beetles are reared in the nests by the ants, who attend to them as carefully as they do to their own young. The beetles have a great fondness for the ants, and prefer to sit amongst a crowd thereof; they are fond of the ants' larvae as food, and indeed eat them to a very large extent, even when their own young are receiving food from the ants. The larva of _Lomechusa_, as described by Wasmann (to whom we are indebted for most of our knowledge of this subject),[105] when not fully grown, is very similar to the larvae of the ants; although it possesses legs it scarcely uses them: its development takes place with extraordinary rapidity, two days, at most, being occupied in the egg, and the larva completing its growth in fourteen days. Wasmann seems to be of opinion that the ants scarcely distinguish between the beetle-larvae and their own young; one unfortunate result for the beetle follows from this, viz. that in the pupal state the treatment that is suitable for the ant-larvae does not agree with the beetle-larvae: the ants are in the habit of digging up their own kind and lifting them out and cleaning them during their metamorphosis; they also do this with the beetle-larvae, with fatal results; so that only those that have the good fortune to be forgotten by the ants complete their development. Thus from thirty _Lomechusa_ larvae Wasmann obtained a single imago, and from fifty _Atemeles_ larvae not even one.

Many other Staphylinidae are exclusively attached to ants' nests, but most of them are either robbers, at warfare with the ants—as is the case with many species of _Myrmedonia_ that lurk about the outskirts of the nests—or are merely tolerated by the ants, not receiving any direct support from them. The most {227}remarkable Staphylinidae yet discovered are some viviparous species, forming the genera _Corotoca_ and _Spirachtha_, that have very swollen abdomens, and live in the nests of Termites in Brazil:[106] very little is, however, known about them. A very large and powerful Staphylinid, _Velleius dilatatus_, lives only in the nests of hornets and wasps. It has been supposed to be a defender of the Hymenoptera, but the recent observations of Janet and Wasmann make it clear that this is not the case: the _Velleius_ has the power of making itself disagreeable to the hornets by some odour, and they do not seriously attack it. The _Velleius_ finds its nutriment in larvae or pupae of the wasps that have fallen from their cells, or in other organic refuse.

The larvae of Staphylinidae are very similar to those of Carabidae, but their legs are less perfect, and are terminated only by a single claw; there is no distinct labrum. The pupae of some are obtected, _i.e._ covered by a secondary exudation that glues all the appendages together, and forms a hard coat, as in Lepidoptera. We have about 800 species of Staphylinidae in Britain, and it is probable that the family will prove one of the most extensive of the Order. It is probable that one hundred thousand species or even more are at present in existence.

FAM. 20. SPHAERIIDAE.—_Very minute. Antennae eleven-jointed, clubbed. Tarsi three-jointed. Abdomen with only three visible ventral segments_. This family includes only three or four species of Insects about 1/50 of an inch long. They are very convex, and be found walking on mud. _S. acaroides_ occurs in our fens. Mr. Matthews considers that they are most nearly allied to Hydrophilidae.[107]

FAM. 21. TRICHOPTERYGIDAE.—_Extremely minute: antennae {228}clavicorn (basal and apical joints thicker than middle joints); tarsi three-jointed; elytra sometimes covering abdomen, in other cases leaving a variable number of segments exposed; wings fringed._ This family comprises the smallest Insects; _Nanosella fungi_ being only 1/100 of an inch long, while the largest Trichopterygid is only 1/12 of an inch. The small size is not accompanied by any degeneration of structure, the minute, almost invisible forms, having as much anatomical complexity as the largest Insects. Very little is known as to the natural history. Probably these Insects exist in all parts of the world, for we have about eighty species in England, and Trichopterygidae are apparently numerous in the tropics.[108]

FAM. 22. HYDROSCAPHIDAE.—_Extremely minute aquatic Insects, with elongate abdomen. Antennae eight-jointed._ The other characters are much the same as those we have mentioned for Trichopterygidae. The family is not likely to come before the student, as only three or four species from Southern Europe and North America are known.[109]

FAM. 23. CORYLOPHIDAE.—_Minute beetles. Tarsi four-jointed, but appearing only three-jointed, owing to the hind joint being concealed by the emarginate (or notched) second joint. Six free ventral segments. Maxillae with only one lobe. Antennae of peculiar form._ There are about 200 species of these little Insects, but the family is apparently represented all over the world, and will probably prove to be much more extensive. The peculiar larva of _Orthoperus brunnipes_ was found abundantly by Perris in thatch in France. Mr. Matthews proposes to separate the genus _Aphanocephalus_ as a distinct family, Pseudocorylophidae.[110] In Corylophidae the wings are fringed with long hairs, as is the case in so many small Insects: the species of _Aphanocephalus_ are rather larger Insects, and the wings are not fringed; the tarsi are only three-jointed.

{229}FAM. 24. SCAPHIDIIDAE.—_Front coxae small, conical; prothorax very closely applied to the after-body; hind coxae transverse, widely separated: abdomen with six or seven visible ventral plates; antennae at the extremity with about five joints that become gradually broader. Tarsi five-jointed._ This family consists of a few beetles that live in fungi, and run with extreme rapidity; they are all small, and usually rare in collections. Some of the exotic forms are remarkable for the extreme tenuity and fragility of the long antennae, which bear fine hairs. The number of described species does not at present reach 200, but the family is very widely distributed. We have three or four species in Britain. All we know of the larvae is a description of that of _Scaphisoma agaricinum_ by Perris;[111] it is like the larva of Staphylinidae, there are nine abdominal segments in addition to a very short, broad pseudopod, and very short cerci. This larva feeds on agarics; it goes through its development in about three weeks; unlike the adult it is not very active.

FAM. 25. SYNTELIIDAE.—_Antennae clavicorn, with very large club: labium, with hypoglottis and the parts beyond it, exposed. Front coxae transverse. Abdomen with five visible ventral segments, and eight or nine dorsal, the basal four of which are semi-corneous._ This family includes only five species; its classification has given rise to much difference of opinion. We have, after consideration of all its characters, established it as a distinct family[112] allied to Silphidae. The perfect Insects live on the sap running from trees: but nothing else is known of their natural history. Like so many others of the very small families of aberrant Coleoptera, it has a very wide distribution; _Syntelia_ being found in Eastern Asia and Mexico, while the sub-family Sphaeritides occurs, as a single species, in Europe and North America. The earlier instars are unknown.

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FAM. 26. HISTERIDAE.—_Very compact beetles, with very hard integument, short, bent antennae, with a very compact club: no hypoglottis. Elytra closely applied to body, but straight behind, leaving two segments exposed. Abdomen with five visible ventral segments; with seven dorsal segments, all hard. Front coxae strongly transverse, hind coxae widely separated._ The extremely compact form, and hard integument, combined with the peculiar antennae—consisting of a long basal joint, six or seven small joints, and then a very solid club of three joints covered with minute pubescence—render these Insects unmistakable. The colour is usually shining black, but there are numerous departures from this. The way in which these Insects are put together so as to leave no chink in their hard exterior armour when in repose, is very remarkable. The mouth-parts are rather highly developed, and the family is entitled to a high rank; it consists at present of about 2000 species;[113] in Britain we have about 40. The larvae are without ocelli or labrum, but have well-developed mandibles, the second and third thoracic segments being short, the ninth segment of the abdomen terminal, with two distinctly jointed cerci.[114] Histeridae are common in dung, in carcases, decaying fungi, etc., and some live under bark—these being, in the case of the genus _Hololepta_, very flat. Some are small cylinders, elaborately constructed, for entering the burrows of Insects in wood (_Trypanaeus_); a certain number are peculiar to ants' nests. Formerly it was supposed that the Insects were nourished on the decaying substances, but it is now believed, with good reason, that they are eminently predaceous, in both larval and imaginal {231}instars, and devour the larvae of Diptera, etc. The relations of the ants'-nest forms to the ants is not made out, but it is highly probable that they eat the ants' larvae, and furnish the ants with some dainty relish. A few species live in company with Termites.

FAM. 27. PHALACRIDAE.—_Body very compact; elytra entirely covering it; apical joints of antennae rather broader, usually long; front coxae globular; posterior coxae contiguous; abdomen with five visible ventral segments; tarsi five-jointed, fourth joint usually small and obscure._ This family consists entirely of small Insects: the tarsal structure is very aberrant, and is also diverse, so that the student may without careful observation pass the Insects over as having only four-jointed tarsi; their structure, so far as the front two pairs are concerned, being very nearly that of many Phytophaga. The larvae live in the heads of flowers, especially of the flowers of Compositae. Having bored their way down the stems, they pupate in earthen cocoons. Heeger[115] says that he has observed in favourable seasons six generations; but the larvae die readily in unfavourable seasons, and are destroyed in vast numbers when the meadows are mowed. Seven years ago very little was known as to the family, and the list of their species scarcely amounted to 100, but now probably 300 are described. They occur in all parts of the world; we have fourteen in Britain.

FAM. 28. NITIDULIDAE.—_Antennae with a three-jointed club; all the coxae separated, and each with an external prolongation; tarsi five-jointed, the fourth joint smaller than any of the others; abdomen with five visible plates._ These Insects are numerous, about 1600 species being at present known; in many of them the elytra nearly or quite cover the hind body, but in many others they are more or less abbreviated; in this case the Insects may be distinguished from Staphylinidae by the form of their antennae, and the smaller number of visible ventral segments. The habits are very varied, a great many are found on flowers, others are attracted by the sap of trees; some live in carcases. We have about 90 species in Britain; several forms of {232}the genera _Meligethes_ and _Epuraea_ are among the most abundant of our beetles. Most of what is known as to the larvae is due to Perris; several have been found living in flowers; that of _Pria_ haunts the flower of _Solanum dulcamara_ at the junction of the stamens with the corolla; the larva of _Meligethes aeneus_ sometimes occasions much loss by preventing the formation of seed in cultivated Cruciferae, such as Rape. These floricolous larvae grow with great rapidity, and then leave the flowers to pupate in the ground. The larva of _Nitidula_ lives in carcases, though it is not very different from that of _Pria_. The larva of _Soronia_ lives in fermenting sap, and has four hooks curving upwards at the extremity of the body. The curious genus _Cybocephalus_ consists of some very small, extremely convex Insects that live in flowers in Southern Europe; they have only four joints to the tarsi. The perfect Insects of the group Ipides are remarkable from having a stridulating organ on the front of the head. The classification of the well-known genus _Rhizophagus_ has given rise to much discussion; although now usually placed in Nitidulidae, we think it undoubtedly belongs to Cucujidae.

FAM. 29. TROGOSITIDAE.—_Differs from Nitidulidae in the structure of the tarsi; these appear to be four-jointed, with the third joint similar in size and form to the preceding; they are, however, really five-jointed, an extremely short basal joint being present. Hind coxae contiguous. The club of each antenna is bilaterally asymmetric, and the sensitive surface is confined to certain parts of the joints._ There are some 400 or 500 species of Trogositidae, but nearly all of them are exotic. The larvae (Fig. 113, A), are predaceous, destroying other larvae in large numbers, and it is probable that the imagos do the same. The larva of _Tenebroides_ (better known as _Trogosita_) _mauritanica_ is found in corn and flour, and is said to have sometimes been very {233}injurious by eating the embryo of the corn, but it is ascertained that it also devours certain other larvae that live on the corn. This beetle has been carried about by commerce, and is now nearly cosmopolitan. Our three British species of Trogositidae represent the three chief divisions of the family, viz. Nemosomides, Temnochilides, Peltides; they are very dissimilar in form, the Peltides being oval, with retracted head. It is doubtful whether the members of the latter group are carnivorous in any of their stages; it is more probable that they live on the fungi they frequent. Peltidae stand as a distinct family in many works.[116]

FAM. 30. COLYDIIDAE.—_Antennae with a terminal club, tarsi four-jointed, none of the joints broad; front and middle coxae small, globose, embedded; hind coxae transverse, either contiguous or separated; five visible ventral segments, several of which have no movement._ This is a family of interest, owing to the great diversity of form, to the extraordinary sculpture and clothing exhibited by many of its members, and to the fact that most of its members are attached to the primitive forests, and disappear entirely when these are destroyed. We have fifteen species in Britain, but about half of them are of the greatest rarity. There are about 600 species known at present; New Zealand has produced the greatest variety of forms; the forests of Teneriffe are rich in the genus _Tarphius_. The sedentary lives of many of these beetles are very remarkable; the creatures concealing themselves in the crannies of fungus-covered wood, and scarcely ever leaving their retreats, so that it is the rarest circumstance to find them at any distance from their homes. _Langelandia anophthalma_ lives entirely underground and is quite blind, the optic lobes being absent. Some Colydiidae are more active, and enter the burrows of wood-boring Insects to destroy the larvae (_Colydium_). Few of the larvae are known; but all appear to have the body terminated by peculiar hard corneous processes, as is the case with a great variety of Coleopterous larvae that live in wood.[117]

{234}FAM. 31. RHYSODIDAE.—_Tarsi four-jointed; mouth-parts covered by the large mentum; front tibiae notched on the inner edge._ This family consists only of a few species, but is found nearly all over the world in the warm and temperate regions. In many of their characters they resemble the Adephaga, but are very different in appearance and in the mouth. The larvae are not known. Some authorities think these Insects should be placed in the series Adephaga,[118] but it is more probable that they will prove to be amongst the numerous aberrant forms of Coleoptera that approach the various large natural series, without really belonging to them. The three families, Colydiidae, Cucujidae, and Rhysodidae, exhibit relations not only with other families of the Coleoptera Polymorpha, but also with most of the great series; Adephaga, Rhynchophora, Phytophaga, and Heteromera, being each closely approached.

FAM. 32. CUCUJIDAE.—_Tarsi five- or four-jointed, the first joint often short: antennae sometimes clubbed, but more often quite thin at the tip; front and middle coxae deeply embedded, globular, but with an angular prolongation externally; abdomen with five visible ventral segments, all movable._ This family and the Cryptophagidae are amongst the most difficult families to define; indeed it is in this portion of the Clavicorns that an extended and thorough study is most urgently required. The Cucujidae include a great diversity of forms; they are mostly found under the bark of trees, and many of them are very flat. Many of the larvae are also very flat, but Ferris says there is great diversity in their structure: they are probably chiefly carnivorous. There are about 400 species described; we have nearly a score in Britain.

The family Cupesidae of certain taxonomists must be at present associated with Cucujidae, though the first joint of the tarsus is elongate.

{235}FAM. 33. CRYPTOPHAGIDAE.—_Front and middle coxae very small and deeply embedded; antennae with enlarged terminal joints; tarsi five-jointed, the posterior sometimes in the male only four-jointed; abdomen with five visible ventral segments, capable of movement, the first much longer than any of the others._ A small family composed of obscure forms of minute size, which apparently have mould-eating habits, though very little is known on this point and several of the genera (_Antherophagus_, _Telmatophilus_) are found chiefly on growing plants, especially in flowers. Although the imago of _Antherophagus_ lives in flowers, yet the larva has only been found in the nests of bumble-bees; there is reason for believing that the imago makes use of the bee to transport it from the flowers it haunts to the nests in which it is to breed;[119] this it does by catching hold of the bee with its mandibles when the bee visits the flower in which the beetle is concealed. It is strange the beetle should adopt such a mode of getting to its future home, for it has ample wings. We must presume that its senses and instinct permit it to recognise the bee, but do not suffice to enable it to find the bee's nest. Some of the larvae of the genus _Cryptophagus_ are found abundantly in the nests of various wasps, where they are probably useful as scavengers, others occur in the nests of social caterpillars, and they are sometimes common in loose straw; this being the habitat in which Perris found the one we figure.

FAM. 34. HELOTIDAE.—_Front and middle coxal cavities round, with scarcely any angular prolongation externally; all the coxae widely separated; five visible ventral segments, all mobile._ The Insects of this family are closely allied to Trogositidae and Nitidulidae, and have the tarsal structure of the former family; but the Helotidae are different in appearance from any members of either of these two families, and are readily distinguished by the coxal character. They are frequently classified with the Erotylidae, from which they differ by the differently shaped feet, especially by the diminished basal joint. {236}There is but one genus, and for a long time only two or three species were known, and were great rarities in collections; in the last few years the number has been raised to nearly forty.[120] They are remarkable beetles with oblong form, and a somewhat metallic upper surface, which is much sculptured, and possesses four yellow, smooth spots on the elytra. According to Mr. George Lewis they are found feeding at the running sap of trees, but the larvae are not known. Helotidae are peculiar to the Indo-Malayan region (including Japan) with one species in Eastern Africa.

FAM. 35. THORICTIDAE.—_Tarsi five-jointed, none of the joints broad; front coxae small, rather prominent, but not at all transverse; five visible ventral plates, all mobile; metasternum very short; antennae short, with a solid club._ This little family, consisting of the genus _Thorictus_, appears to be a distinct one, though the structure has only been very imperfectly studied. It is peculiar to the Mediterranean region, where the species live in ants' nests. They appear to be on terms of great intimacy with the ants; a favourite position of the beetle is on the scape of the antenna of an ant; here it hooks itself on firmly, and is carried about by the ant. Like so many other ants'-nest beetles, Thorictidae possess tufts of golden hair, which secrete some substance, the flavour of which is appreciated by the ants; these tufts in Thorictidae are situated either at the hind angles of the pronotum, or on the under surface of the body on each side of the breast; Wasmann thinks that when the beetles are riding about, as above described, the ants have then an opportunity of getting at the patches on the under surface.

FAM. 36. EROTYLIDAE.—_Tarsi five-jointed, but with the fourth usually very small, the first three more or less broad and pubescent beneath. Antennae strongly clubbed. Front and middle coxal acetabula round, without angular prolongation externally; five visible ventral segments._ This is now a large and important family of about 1800 species, but it is chiefly exotic and tropical, its members haunting the fungoid growths {237}in forests. We have only six species in Britain, and the whole of Europe has only about two dozen, most of them insignificant (and in the case of the Dacnides aberrant, approaching the Cryptophagidae very closely). The sub-family Languriides (quite wanting in Europe) consists of more elongate Insects, with front acetabula open behind; they have different habits from Erotylides proper; some are known to live as larvae in the stems of herbaceous plants. They possess a highly developed stridulating organ on the front of the head. The Clavicorn Polymorpha are very closely connected with the Phytophaga by Languriides.

FAM. 37. MYCETOPHAGIDAE.—_Tarsi four-jointed, slender, the front feet of the male only three-jointed; coxae oval, not deeply embedded; abdomen with five ventral segments, all movable._ A small family, of interest chiefly because of the anomaly in the feet of the two sexes, for which it is impossible to assign any reason. The species are small, uninteresting Insects that live chiefly on Cryptogams of various kinds, especially in connection with timber; the larvae being also found there. There are about a dozen species in Britain, and scarcely 100 are described from all the world. The Diphyllides, placed by Leconte and Horn in this family, seem to go better in Cryptophagidae.

FAM. 38. COCCINELLIDAE (_Lady-birds_).—_Tarsi apparently three-jointed; the first two joints pubescent beneath; the third joint consisting really of two joints, the small true third joint being inserted near the base of the second joint, the upper surface of which is grooved to receive it. Head much concealed by the thorax. Antennae feebly clubbed._ The lady-birds number fully 2000 species. The structure of their feet distinguishes them from nearly all other Coleoptera except Endomychidae, which are much less rotund in form, and have larger antennae. One genus of Endomychids—_Panomoea_—bears, however, a singular resemblance to lady-birds, both in form and style of coloration. Several species of Coccinellidae are remarkable on account of the numerous variations in colour they present. Coccinellidae frequently multiply to an enormous extent, and are of great value, as they destroy wholesale the plant-lice, scale-Insects, {238}and Acari that are so injurious to cultivated plants. They also eat various other soft-bodied Insects that attack plants. As they are excessively voracious, and are themselves singularly free from enemies and multiply with great rapidity, all these features of their economy render them of inestimable value to the agriculturist and horticulturist. The species of the sub-family Epilachnides feed on plants, and one or two are occasionally injurious. The body-fluid of Coccinellidae has an unpleasant odour and taste. Many lady-birds have the power of exuding, when disturbed, small quantities of a yellow fluid. Lutz has shown that this is not a special secretion, but an exudation of the fluid of the body that takes place through a small orifice at the tip of the tibia, from pressure caused by contraction of the body and limb.[121]

The larvae are much more active than beetle-larvae usually are, and many of them are very conspicuous when running about on plants to hunt their prey. They usually cast their skins three times, and sometimes concomitantly change a good deal in colour and form; the larval life does not usually exceed four or five weeks; at the end of which time the larva suspends itself by the posterior extremity, which is glued by a secretion to some object; the larval skin is pushed back to the anal extremity, disclosing the pupa; this differs in several respects from the usual pupa of beetles; it is harder, and is coloured, frequently conspicuously spotted, and dehisces to allow the escape of the beetle, so that the metamorphosis is altogether more like that of Lepidoptera than that of Coleoptera. There is much variety in the larvae; some of them bear large, complexly-spined, projections; those of the group Scymnites have small depressions on the surface, from which it has been ascertained that waxy secretions exude; but in _Scymnus minimus_ no such excretions are formed. Certain species, when pupating, do not shuffle the skin to the extremity of the body, but retain it as a covering for the pupa. The larvae that feed on plants are much less active than the predaceous forms. We are well supplied with Coccinellidae in Britain, forty species being known here.

The systematic position of Coccinellidae amongst the Coleoptera has been for long a moot point. Formerly they were associated with various other beetles having three-jointed, or apparently three-jointed, feet, as a series with the name Trimera, or {239}Pseudotrimera. But they are generally placed in the Clavicorn series, near Endomychidae. Verhoeff has recently made considerable morphological studies on the male genital organs of Coleoptera, and as the result, he concludes that Coccinellidae differ radically from all other Coleoptera as regards these structures, and he therefore treats them as a distinct series or sub-order, termed Siphonophora. The genus _Lithophilus_ has been considered doubtfully a member of Coccinellidae, as the tarsi possess only in a slight degree the shape characteristic of the family: Verhoeff finds that they are truly Coccinellidae, forming a distinct division, Lithophilini; and our little species of _Coccidula_, which have somewhat the same appearance as Lithophilini, he treats as another separate group, Coccidulini.

FAM. 39. ENDOMYCHIDAE.[122]—_Tarsi apparently three-jointed, the first two joints broad, the terminal joint elongate; at the base of the terminal joint there is, however, a very small joint, so that the tarsi are pseudotetramerous; antennae rather large, with a large club; labium not at all retracted behind the mentum; front and middle coxae globose; abdomen with five movable ventral segments, and a sixth more or less visible at the tip._ This family includes a considerable diversity of elegant Insects that frequent fungoid growths on wood. It comprises at present fully 500 species, but nearly the whole of them are exotic, and inhabit the tropical forests. We have only two British species, both of which are now rarities, but apparently were much commoner at the beginning of the century. The larvae are broader than is usual in Coleoptera; very few, however, are known.

FAM. 40. MYCETAEIDAE.—_Tarsi four-jointed, the first two joints not very different from the third, usually slender; abdomen with five visible ventral segments, which are movable; front and middle coxae globular._ The little Insects composing this family are by many placed as a division of Endomychidae, and Verhoeff is of opinion that the group is an altogether artificial one; but we think, with Duval, it makes matters simpler to separate them. There are only {240}some forty or fifty species, found chiefly in Europe and North America. We have three in Britain; one of these, _Mycetaca hirta_ is very common, and may be found in abundance in cellars in the heart of London, as well as elsewhere; it is said to have injured the corks of wine-bottles, and to have caused leakage of the wine, but we think that it perhaps only increases some previous deficiency in the corkage, for its natural food is fungoid matters. The larva is remarkable on account of the clubbed hairs at the sides of the body.

FAM. 41. LATRIDIIDAE.—_Tarsi three-jointed; anterior coxal cavities round, not prolonged externally; abdomen with five visible and mobile ventral segments._ Very small Insects, species of which are numerous in most parts of the world, the individuals being sometimes very abundant. The larvae (Fig. 120, A) are said by Perris to have the mandibles replaced by fleshy appendages. The pupa of _Latridius_ is remarkable, on account of the numerous long hairs with heads instead of points; the larva of _Corticaria_ is very like that of _Latridius_, but some of the hairs are replaced by obconical projections. The sub-family Monotomides is by many treated as a distinct family; they have the elytra truncate behind, exposing the pygidium, and the coxae are very small and very deeply embedded. Most of the Latridiidae are believed to live on fungoid matters; species of _Monotoma_ live in ants' nests, but probably have no relations with the ants. A few species of Latridiides proper also maintain a similar life; _Coluocera formicaria_ is said to be fond of the stores laid up by _Aphaenogaster structor_ in its nests. About 700 species are now known; scarcely any of the individuals are more than one-tenth of an inch long. We have about 40 species in Britain. The North American genus _Stephostethus_ has the prosternum constructed behind the coxae, somewhat in the same manner as it is in the Rhynchophorous series of Coleoptera.

FAM. 42. ADIMERIDAE.—_Tarsi appearing only two-jointed, a broad basal joint and an elongate claw-bearing joint, but between the two there are two very small joints._ This family consists only of the American genus _Adimerus_; nothing is known of {241}the life-history of these small Insects. They are of some interest, as this structure of the foot is not found in any other beetles.

FAM. 43. DERMESTIDAE.—_Tarsi five-jointed; antennae usually short, with the club frequently very large in proportion, and with the under side of the thorax bearing a hollow for its reception. Front coxae rather long, oblique: hind coxa formed to receive the femur when in repose._ A family of 300 or 400 species of small or moderate-sized beetles; the surface, usually covered with fine hair, forming a pattern, or with scales. _Byturus_, the position of which has long been disputed, has now been placed in this family; it has a more imperfectly formed prosternum, and the third and fourth joints of the tarsi are prolonged as membranous lobes beneath; the hind coxae leave the femora quite free. Dermestidae in the larval state nearly all live on dried animal matter, and are sometimes very destructive; some of them totally destroy zoological collections. They are very remarkable on account of the complex clothing of hairs they bear; they have good powers of locomotion, and many of them have a peculiar gait, running for a short distance, then stopping and vibrating some of their hairs with extreme rapidity. They exhibit great variety of form. Many of them are capable of supporting life for long periods on little or no food, and in such cases moult an increased number of times: pupation takes place in the larval skin. _Anthrenus fasciatus_ has been reared in large numbers on a diet of dried horse-hair in furniture. The young larva of this species observed by the writer did not possess the remarkable, complex arrangement of hairs that appeared when it was further grown. The most curious of Dermestid larvae is that of _Tiresias serra_, which lives amongst cobwebs in {242}old wood, and probably feeds on the remains of Insects therein, perhaps not disdaining the cobwebs themselves. Attention has been frequently called to the hairs of the larvae of these Insects, but they have never been adequately discussed, and their function is quite unknown.

FAM. 44. BYRRHIDAE (_Pill-beetles_).—_Oval or round, convex beetles; tarsi five-jointed, front coxae not exserted, transverse; hind coxa shielding the retracted femur. The whole of the appendages capable of a complete apposition to the body._ Although a small family of only 200 or 300 species, Byrrhidae are so heterogeneous that no characteristic definition that will apply to all the sub-families can be framed. Very little is known as to their life-histories. _Byrrhus pilula_ is one of our commonest beetles, and may be found crawling on paths in early spring even in towns; it moves very slowly, and when disturbed, at once contracts the limbs so completely that it looks like an inanimate object. The larva is cylindrical, soft; the prothoracic and last two abdominal segments are larger than the others, the last bearing two pseudopods; its habits are unknown, and no good figure exists of it.

The chief groups of Byrrhidae are Nosodendrides, Byrrhides (including Amphicyrtides), Limnichides, and Chelonariides. The first consists of species frequenting the exuding sap of trees; they have an unusually large mentum, abruptly clubbed antennae, and the head cannot be retracted and concealed. The genus _Nosodendron_ seems to be distributed over a large part of the world. The Byrrhides have the antennae gradually thicker towards the tip, the mentum small, and the head and thorax so formed that the former can be perfectly retracted. The species are rather numerous, and are found in the northern and antipodeal regions, being nearly completely absent from the tropics. The Limnichides are minute Insects living in very moist places; they have small delicate antennae, which are imperfectly clubbed. The group is very widely distributed.

The Chelonariides are a very peculiar form of Coleoptera: oval Insects of small size with the prothorax so formed that the head can be withdrawn under (rather than into) it, and then abruptly inflexed, so that the face then forms part of the under surface: the antennae have the basal three joints thicker than the others; these being not in the least clubbed, but having the {243}joints so delicately connected that the organs are rarely unmutilated. The modifications of the head and prothorax are quite unlike those of other Byrrhidae, and if the Chelonariides do not form a distinct family, they should be associated with Dascillidae. Nothing is known as to the earlier stages. They are chiefly tropical Insects, though one species is found in North America.

FAM. 45. CYATHOCERIDAE.—_Minute Insects of broad form; parts of the mouth concealed; antennae four-jointed; tarsi not divided into joints; prosternum small._ The only species of this aberrant family, _Cyathocerus horni_, has been found in Central America. Nothing is known as to its life-history.

FAM. 46. GEORYSSIDAE.—_Antennae short, clubbed; tarsi four-jointed; prosternum very small; front coxae exserted, but not contiguous._ There are about two dozen species of these small beetles known. Our British _Georyssus pygmaeus_ lives in extremely wet places, and covers itself with a coating of mud or fine sand so that it can only be detected when in movement. Nothing further is known as to its life-history or habits. Members of the genus have been detected in widely-separated parts of the globe.

FAM. 47. HETEROCERIDAE.—_Labrum and mandibles projecting forwards; antennae short, the terminal seven joints broad and short, forming a sort of broad serrate club; legs armed with stout spines; tarsi four-jointed._ The Heteroceridae are small beetles covered with very dense but minute pubescence; they live in burrows among mud or sand in wet places, and are found in many parts of the world. They possess a stridulating organ in the form of a slightly elevated curved line on each side of the base of the abdomen, rubbed by the posterior femur. The larvae live in the same places as the beetles; they have well-developed thoracic legs, the mandibles are porrect, the three thoracic segments rather large, and the body behind these becomes gradually narrower; they are believed to eat the mud amongst which they burrow. We have seven British species of Heteroceridae.