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HETEROMERA

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Originally appearing in Volume V06, Page 675 of the 1911 Encyclopedia Britannica.
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HETEROMERA .—ThiS tribe is distinguished by the presence of the normal five segments in the feet of the fore and intermediate legs, while only four segments are visible in the See also:

hind-See also:foot. Considerable diversity is to be noticed in details of structure within this See also:group, and for an enumeration of all the various families which have been proposed and their distinguishing characters the reader is referred to one of the monographs mentioned below. Some of the best-known members of the group belong to the Tenebrionidae, a large FIG. 21.-(a) Tenebrio molitor FIG. 22.—Blaps mortisaga (See also:Flour See also:Beetle). See also:Europe. (b) (See also:Churchyard Beetle). Europe. Larva, or mealworm. See also:family containing over Io,000 See also:species and distributed all over the See also:world. The tenebrionid larva is elongate, with well-chitinized cuticle, See also:short legs and two stumpy tail processes, the See also:common See also:meal-See also:worm (fig. 21) being a See also:familiar example.

Several species of this family are found habitually in stores of flour or See also:

grain. The beetles have feelers with eleven segments, whereof the terminal few are thickened so as to See also:form a See also:club. The true " See also:black-beetles " or " churchyard beetles " (Blaps) (fig. 22) belong to this family; like members of several allied genera they are sooty in See also:colour, and some-what resemble ground beetles (Carabi) in See also:general See also:appearance. The most interesting of the Heteromera, and perhaps of all the See also:Coleoptera, are some beetles which pass through two or more larval forms in the course of the See also:life-See also:history (hypermetamorphosis). These belong to the families Rhipidophoridae and Meloidae. The latter are the oil beetles (fig. 23) or See also:blister beetles (fig. 24), See also:insects with rather soft cuticle, the elytra (often abbreviated) not fitting closely to the sides of the See also:abdomen, the See also:head constricted behind the eyes to form (Oil Beetle). Europe. (Blister Beetle). Europe.

' a See also:

neck, and the claws of the feet divided to the See also:base. Several of the Meloidae (such as the " See also:Spanish See also:fly," fig. 24) are of economic importance, as they contain a vesicant substance used for raising medicinal blisters on the human skin. The wonderful transformations of these insects were first investigated by G. See also:Newport in 1851, and have recently been more fully studied by C. V. See also:Riley (1878) and J. H. See also:Fabre. The first larval See also:stage is the " triungulin," a tiny, active, armoured larva with See also:long legs (each foot with three claws) and cercopods. In the See also:European species of Sitaris and Meloe these little larvae have the See also:instinct of clinging to any hairy See also:object. All that do not happen to attach themselves to a See also:bee of the genus Anthophora perish, but those that succeed in reaching the right See also:host are carried to the See also:nest, and as the bee See also:lays an See also:egg in the See also:cell the triungulin slips off her See also:body on to the egg, which floats on the See also:surface of the See also:honey.

After eating the contents of the egg, the larva moults and becomes a fleshy See also:

grub with short legs and with paired spiracles See also:close to the dorsal region, so that, as it floats in and devours the a honey, it obtains a See also:supply of See also:air. After a resting (pseudo-pupal) stage and another larval stage, the pupa is See also:developed. In the See also:American Epicauta vittata the larva is parasitic on the eggs and egg-cases of a See also:locust. The triungulin searches for the eggs, and, after a See also:moult, becomes changed into a soft-skinned tapering larva. This is followed by a resting (pseudo-pupal) stage, and this by two successive larval stages like the grub of a See also:chafer. The Rhipidophoridae are beetles with, short elytra, the feelers pectinate in the malesand serrate in the See also:females. The life-history of Metoecus has been studied by T. A. See also:Chapman, who finds that the eggs are laid in old See also:wood, and that the triungulin seeks to attach itself to a social See also:wasp, who carries it to her nest. There it feeds first as an See also:internal See also:parasite of the wasp-grub, then bores its way out, moults and devours the wasp larva from outside. The wasps are said to leave the larval or pupal Metoecus unmolested, but they are hostile to the developed beetles, which hasten to leave the nest as soon as possible. ST REPSIPTERA.-MUCh difference of See also:opinion has prevailed with regard to the curious, tiny, parasitic insects included in this See also:division, some authorities considering that they should be referred to a distinct See also:order, while others would group them in the family Meloidae just described.

While from the nature of their life-history there is no doubt that they have a rather close relationship to the Weloidae, their structure is so remarkable that it seems advisable fo regard them as at least a distinct tribe of Coleoptera. They may be comprised in a single family, the Stylopidae. The See also:

males are very small, See also:free-flying insects with the prothorax, mesothorax and elytra greatly reduced, the latter appearing as little, See also:twisted strips, while the metathorax is relatively large, with its wings broad and capable of See also:longitudinal folding. The feelers are branched and the jaws vestigial. The See also:female is a segmented, worm-like creature, spending her whole life within the body of the bee, wasp or See also:hug on which she is parasitic. One end of her body protrudes from between two of the abdominal segments of the host; it has been a subject of dispute whether this protruded end is the head or the tail, but there can be little doubt that it is the latter. While thus carried about by the host-See also:insect, the female is fertilized by the free-flying male, and gives See also:birth to a number of tiny triungulin larvae. The See also:chief points in the life-history of Stylops and Xenos, which are parasitic on certain bees (Andrena) and wasps (Polistes), have been investigated by K. T. E. von See also:Siebold (1843) and N. Nassonov (1892). The little triungulins See also:escape on to the body of the bee or wasp; then those that are to survive must leave their host for a non-parasitized insect.

Clinging to her hairs they are carried to the nest, where they See also:

bore into the body of a bee or wasp larva, and after a moult become soft-skinned legless maggots. The growth of the parasitic larva does not stop the development of the host-larva, and when the latter pupates and assumes the winged form, the stylopid, which has completed its transformation, is carried to the See also:outer world. The presence of a Stylops causes derangement in the body of its host, and can he recognized by various See also:external signs. Other genera of the family are parasitic on See also:Hemiptera —bugs and See also:frog-hoppers—but nothing is known as to the details of their life-history. I.AMELLICORNIA.—This is a very well-marked tribe of beetles, characterized by the See also:peculiar See also:elongation and flattening of three or more of the terminal antennal segments, so that the feeler seems to end in a number of See also:leaf-like plates, or small See also:comb-See also:teeth (fig. 26, b, c). The wings are well developed for See also:flight, and there is a tendency in the group, especially among the males, towards an excessive development of the mandibles or the presence of enormous, See also:horn-like processes on the head or pronotum. There are four malpighian tubes. The larvae are furnished with large heads, powerful mandibles and well-developed legs, but the body-segments are feebly chitinized, and the tail-end is swollen. They feed in wood or spend an under-ground life devouring roots or See also:animal excrement. The Lucanidae or See also:stag beeties (See also:figs. 1 and 25) have the terminal antennal segments pectinate, and so arranged that the comb-like See also:part of the feeler cannot be curled up, while the elytra completely See also:cover the abdomen.

There are about 600 species in the family, the males being usually larger than the females, and remarkable for the See also:

size of their mandibles. In the same species, however, See also:great variation occurs in the development of the mandibles, and the breadth of the head varies correspondingly, the smallest type of male being but little different in appearance from the female. The larvae of Lucanidae live within the wood of trees, and may take three or four years to attain their full growth. The Passalidae are a tropical family of beetles generally considered to be intermediate between stag-beetles and chafers, the enlarged segments of the feeler being capable of close approximation. The Scarabaeidae or chafers are an enormous family of about 15,000 species. The See also:plate-like segments of the feeler (fig. 26, b, c) can be brought close together so as to form a club-like termination; usually the hinder abdominal segments are not covered by the elytra. In this family there is often a marked divergence between the sexes; the terminal antennal segments are larger in the male than in the female, and the males may carry large spinous processes on the head or prothorax, or both. These structures were believed by C. See also:Darwin to he explicable by sexual selection. The larvae have the three pairs of legs well developed, and the hinder abdominal segments swollen. Most of the Scarabaeidae are See also:vegetable-feeders, but one See also:section VI.

22of the family—represented in temperate countries by the dorbeetles (Geotrupes) (fig. 28) and Aphodius, and in warmer regions by the " sacred " beetles of the Egyptians (Scarabaeus) (fig. 27), and allied genera—feed both in the adult and larval stages, on dung or decaying animal See also:

matter. The heavy grubs of Geotrupes, their See also:Java. Antenna of male; c, antenna of female. swollen tail-ends black with the contained See also:food-material, are often dug up in See also:numbers in well-manured See also:fields. The habits of Scarabaeus have been described in detail by J. H. Fabre. The female beetle in See also:spring-See also:time 'collects dung, which she forms into a See also:ball by continuous See also:rolling, sometimes assisted by a See also:companion. This ball is buried in a suitable See also:place, and serves the insect as a See also:store of food. During summer the insects See also:rest in their underground retreats, then inautumn Aegyptiorum.

See also:

Africa. burnei. N. See also:America. they reappear to See also:bury another supply of dung, which serves as food for the larvae. Fabre states that the See also:mother-insect carefully arranges the food-supply so that the most nutritious and easily digested portion is nearest the egg, to form the first meal of the See also:young larva. In some species of Copris it is stated that the female S. America. W. Africa. lays only two or three eggs at a time, watching the offspring grow to maturity, andihen rearing another brood. Among the vegetable-feeding chafers we usually find that while the perfect insect devours leaves, the larva lives underground and feeds on roots. Such are the habits of the cockchafer (Melolontha vulgaris) and other species that often cause great injury to See also:farm and II c b a See also:garden crops (see CHAFER).

Many of these insects, such as the species of Phanaeus (fig. 29) and Cetonia (fig. 30), are adorned with metallic or other brilliant See also:

colours. The See also:African " See also:goliath-beetles " (fig. 31) and the American " See also:elephant-beetles " (Dynastes) are the largest of all insects. ANCHIsT0P0DA.—The families of beetles included by See also:Kolbe in this group are distinguished by the See also:possession of six malpighian tubes, and a great reduction in one or two of the tarsal segments, so that there seem to be only four or three segments in each foot; hence the names Tetramera and Trimera formerly applied to them. The larvae have soft-skinned bodies sometimes protected by rows of spiny tubercles, the legs being fairly developed in some families and greatlysegments to the foot, but there are really five, the See also:fourth being greatly reduced. The mandibles are strong, adapted for biting the vegetable substances on which these beetles feed, and the palps of the second maxillae have three segments. Most of the Chrysomelidae are metallic in colour and See also:convex in form; in some the head is concealed beneath the prothorax, and the so-called " See also:tortoise " beetles (Cassidinae) have the elytra raised into a prominent median See also:ridge. The most active form of larva found in this family resembles in shape that of a ladybird, tapering towards the tail end, and having the See also:trunk segments protected by small See also:firm sclerites. Such larvae, and also many with soft cuticle and swollen abdomen—those of the notorious " See also:Colorado beetle," for example—feed openly reduced or absent in others. As might be expected, degeneration in larval structure is correlated with a concealed See also:habit of life.

The Coccinellidae, or ladybirds (fig. 32), are a large family of beetles, well known by their rounded convex bodies, usually shining and hairless. They have eleven segments to the feeler, which is clubbed at the tip, and apparently three segments only in each foot. Ladybirds are often brightly marked with spots and dashes, their coloration being commonly regarded as an See also:

advertisement of in-edibility. The larvae have a somewhat swollen abdomen, which is protected by bristle-bearing tubercles. Like the perfect insects, they are predaceous, feeding on plant-lice (Aphidae) and See also:scale insects (Coccidae). Their role in nature is therefore beneficial to the See also:cultivator. The Endomychidae (fig. 33), an allied family, are mostly fungus-eaters. In the Erotylidae and a few other small related families the feet are evidently four-segmented. The Chrysomelidae, or leaf-beetles (figs. 34, 35), are a very large family, with " tetramerous " tarsi; there seem to be only four on foliage.

Others, with soft, See also:

white, cylindrical bodies, which recall the caterpillars of moths, burrow in the leaves or stems of See also:plants. The larvae of the tortoise-beetles have the curious habit of forming an See also:umbrella-like See also:shield out of their own excrement, held in position by the upturned tail-See also:process. The larvae of the beautiful, elongate, metallic Donaciae live in the roots and stems of aquatic plants, obtaining thence both food and air. The larva pierces the vessels of the plant with See also:sharp processes at the hinder end of its body. In this way it is believed that the sub-aqueous cocoon in which the pupal stage is passed becomes filled with air. The Cerambycidae, or longhorn beetles, are recognizable by their slender, elongate feelers, which are never clubbed and rarely serrate. The foot has apparently four segments, as in the Chrysomelidae. The beetles are usually elongate and elegant in form, often adorned with See also:bright bands of colour, and some of the tropical species attain a very large size (figs. 36, 37). The feelers are usually longer in the male than in the female, exceeding in some cases by many times the length of the body. The larvae have soft, fleshy bodies, with the head and prothorax large and broad, and the legs very much reduced. They live and feed in the wood of trees.

Consequently, beetles of this family are most abundant in See also:

forest regions, and reach their highest development in the dense virgin forests of tropical countries, See also:South America being particularly See also:rich in peculiar genera. The Bruchidae, or See also:seed-beetles, agree with the two preceding families in tarsal structure; the head is largely hidden by the pronotum, and the elytra are short enough to leave the end of the abdomen exposed (fig. 38). The development of the See also:pea and See also:bean-beetles has been carefully studied by C. V. Riley, who finds that the young larva, hatched from the egg laid on the pod, has three pairs of legs, and that these are lost after the moult that occurs when the grub has bored its way into the seed. In Great See also:Britain the beetle, after completing its development, winters in the seed, waiting to emerge and See also:lay its eggs on the blossom in the ensuing spring. (Pea Beetle.) Europe. latirostris. Europe. RHYxcHOPHORA.—The Rhynchophora are a group of beetles easily recognized by the elongation of the head into a See also:beak or snout, which carries the feelers at its sides and the jaws at its tip. The third tarsal segment is broad and bi-lobed, and the fourth is so small that the feet seem to be only four-segmented. There are six malpighian tubes.

The ventral scleriteof the head-See also:

skeleton (See also:gula), well developed in most families of beetles, is absent among the Rhynchophora, while the palps of the maxillae are much reduced. The larvae have soft, white bodies and, with very few exceptions, no legs. Of the four families included in this group, the Anthribidae (fig. 39) have jointed, flexible palps, feelers—often of excessive length—with a short basal segment, and the three terminal segments forminga club, and, in some genera, larvae with legs. There are nearly 1000 known species, most of which live in tropical countries. The Brenthidae are a remarkable family almost confined to the tropics; they are elongate and narrow in form (fig. 40), with a straight, cylindrical snout which in some male beetles of the family is longer than the rest of the body. The Curculionidae, or weevils (q.v.), comprising 23,000 species, are by far the largest family of the group. The maxillary palps are short and rigid, and there is no distinct See also:labrum, while the feelers are usually of an " elbowed " form, the basal segment being very elongate (figs. 41, 42). They are vegetable feeders, both in the perfect and larval stages, and are often highly injurious. The female uses her snout as a See also:boring See also:instrument to prepare a suitable place for egg-laying.

The larvae (fig. 3) of some weevils live in seeds; others devour roots, while the See also:

parent-beetles eat leaves; others, again, are found in wood or under bark. The Scolytidae, or bark-beetles, are a family of some 1500 species, closely allied to the Curculionidae, differing only in the feeble development of the snout. They have clubbed feelers, and their cylindrical bodies (fig. 43) are well adapted for their burrowing habits under the bark of trees. Usually the mother-beetle makes a fairly straight See also:tunnel along which, at short intervals, she lays her eggs. The grubs, when hatched, start galleries nearly at right angles to this, and when fully grown form See also:oval cells in which they pupate; from these the young beetles emerge by making circular holes directly outward through the bark. The wings of Coleoptera (including the elytra) are described and discussed by F. Meinert (Entom. Tijdsk. v., 1880) ; C. Hoffbauer (Zeit. f. wissen. Zool. liv., 1892) ; J.

H. Comstock and J. G. Needham (Amer. Nat. xxxii., 1898) ; and W. L. See also:

Tower (Zool. Jahrb. Anat. xvii., 1903). The See also:morphology of the abdomen, ovipositor and genital See also:armature is dealt with by K. W. Verhoeff (Ent.

Nachtr. xx., 1894, and See also:

Arch. f. Naturg. lxi., lx11., 1895–1896) ; and B. Wandolleck (Zool. Jahrb. Anat. xxii., 1905). Luminous See also:organs are described by H. von Wielowiejski (Zeits. f. wissen. Zool. See also:xxxvii., 1882) ; C. Heinemann (Arch. f. mikr. Anat. See also:xxvii., 1886) ; and R. See also:Dubois (See also:Bull. See also:soc. zeol. See also:France, 1886) ; and stridulating organs by C. J.

Gahan (Trans. Entom. Soc., 1900). See also C. Darwin's Descent of See also:

Man and Selection in Relation to See also:Sex (See also:London, 1871). Many larvae of Coleoptera are described and beautifully figured by J. C. Schiodte (Naturh. Tidsskr. i.-xiii., 1861–1872). Hyper-See also:metamorphosis in the Meloidae is described by G. Newport (Trans. Linn.

Soc. xx., xxi., 1851–1853) ; C. V. Riley (See also:

Rep. U.S. Entom. See also:Comm. i., 1878); J. H. Fabre (See also:Ann. Sci. Nat. (4), ix., xix., 1848–1853) ; H. See also:Beauregard (See also:Les Insectes vesicants, See also:Paris, 189o) ; and A.

Chabaud (Ann. Soc. Ent. France, lx., 1891) ; in the Bruchidae by Riley (Insect Life, iv., v., 1892–1893; and in the Strepsiptera (Stylopidae) by K. T. E. von Siebold (Arch. f. Naturg. ix., 1843) ; N. Nassonov (Bull. Univ. Narsovie, 1892) ; and C. T. Brues (Zool.

Jahrb. Anat. xiii., 1903). For various schemes of See also:

classification of the Coleoptera see E. L. See also:Geoffroy (Insectes qui se trouvent aux environs de Paris, Paris, 1762) ; A. G. See also:Olivier (Coleopteres, Paris, 1789--18o8); W. S. MacLeay (Annulosa Javanica, London, 1825) ; the general See also:works of Westwood and Sharp, mentioned above; M. Gemminger and B. de Harold (Catalogus Coleopterorum, 12 vols., See also:Munich, 1868–1872); T. See also:Lacordaire and F. Chapuis (Genera See also:des Coleopteres, to vols., Paris, 1854–1874) ; J.

L. Leconte and G. H. Horn (Classification of Coleoptera of N. America, See also:

Washington, Smithsonian Inst., 1883); L. Ganglbauer (See also:Die Keifer von Mitteleuropa, See also:Vienna, 1892, &c.) ; A. Lameere (Ann. Soc. Ent. Belg. xliv., xxvii., 1900–1903) ; and H. J. Kolbe (Arch. f.

Naturg. lxvii., 1901). For the See also:

British species, W. W. See also:Fowler (Coleoptera of the British Islands, 5 vols., London, 1887–1891) is the See also:standard See also:work; and W. F. See also:Johnson and J. N. See also:Halbert's " Beetles of See also:Ireland " (Prot. R. Irish Acad., 3, vi., 1902) is valuable faunistically. Among the large number of systematic writers on the order generally, or on See also:special families, may be mentioned D. Sharp, T.

V. See also:

Wollaston, H. W. See also:Bates, G. C. See also:Champion, E. Reitter, G. C. See also:Crotch, H. S. Gorham, M. Jacoby, L.

Fairmaire and C. O. See also:

Waterhouse. (G. H.

End of Article: HETEROMERA

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