HOMOPTERA

this sub-order includes the cicads, lantern-flies, frog-hoppers, aphids and scale-insects. the face has such a marked backward slope (see fig. 1) as to bring the beak into close contact with the haunches of the fore-legs. the feelers have one or more thickened basal segments, while the remaining segments are slender and thread-like. the fore-wings are sometimes membranous like the hind-wings, usually they are firmer in texture, but they never show the distinct areas that characterize the wings of heteroptera. when at rest the wings of homoptera slope roofwise across the back of the insect. in their life-history the homoptera are more specialized than the heteroptera; the young insect often differs markedly from its parent and does not live in the same situations; while in some families there is a passive stage before the last moult. [illustration: after weed, riley and howard, _insect life_, vol iii. fig. 11.--cabbage aphid (_aphisbrassicae_). a, male; c, female (wingless). magnified. b and d, head and feelers of male and female, more highly magnified.] [illustration: after howard, _year book u.s. dept. agr._, 1894. fig. 12.--apple scale insect (_mytilaspis pomorum_). a, male; e, female; c, larva magnified--; b, foot of male; d, feeler of larva, more highly magnified.] the _cicadidae_ are for the most part large insects with ample wings; they are distinguished from other homoptera by the front thighs being thickened and toothed beneath. the broad head carries, in addition to the prominent compound eyes, three simple eyes (ocelli) on the crown, while the feeler consists of a stout basal segment, followed by five slender segments. the female, by means of her serrated ovipositor, lays her eggs in slits cut in the twigs of plants. the young have simple feelers and stout fore-legs (fig. 10) adapted for digging; they live underground and feed on the roots of plants. in the case of a north american species it is known that this larval life lasts for seventeen years. the "song" of the male cicads is notorious and the structures by which it is produced have already been described (see also cicada). there are about 900 known species, but the family is mostly confined to warm countries; only a single cicad is found in england, and that is restricted to the south. the _fulgoridae_ and _membracidae_ are two allied families most of whose members are also natives of hot regions. the _fulgoridae_ have the head with two ocelli and three-segmented feelers; frequently as in the tropical "lantern-flies" (q.v.) the head is prolonged into a conspicuous bladder, or trunk-like process. the _membracidae_ are remarkable on account of the backward prolongation of the pronotum into a process or hood-like structure which may extend far behind the tail-end of the abdomen. two other allied families, the _cercopidae_ and _jassidae_, are more numerously represented in our islands. the young of many of these insects are green and soft-skinned, protecting themselves by the well-known frothy secretion that is called "cuckoo-spit." [illustration: after howard, _year book u.s. dept. agr._, 1894. fig. 13.--apple scale insect (_mytilaspis pomorum_). a, scale from beneath showing female and eggs; b, from above, magnified--; c and e, female and male scales on twigs, natural size; d, male scale magnified.] [illustration: from osborn (after denny), _bull._ 5 (n.s.), _div. ent. u.s. dept. agr._ fig. 14.--louse (_pediculus vestimenti_). magnified.] [illustration: from osborn (after schiodte), _bull._ 5; (n.s.), _div. ent. u.s. dept. agr._ fig. 15.--proboscis of pediculus. highly magnified.] in all the above-mentioned families of homoptera there are three segments in each foot. the remaining four families have feet with only two segments. they are of very great zoological interest on account of the peculiarities of their life-history--parthenogenesis being of normal occurrence among most of them. the families _psyllidae_ (or "jumpers") with eight or ten segments in the feeler and the _aleyrodidae_ (or "snowy-flies") distinguished by their white mealy wings, are of comparatively slight importance. the two families to which special attention has been paid are the _aphidae_ or plant-lice ("green fly") and the _coccidae_ or scale-insects. the aphids (fig. 11) have feelers with seven or fewer distinct segments, and the fifth abdominal segment usually carries a pair of tubular processes through which a waxy secretion is discharged. the sweet "honey-dew," often sought as a food by ants, is secreted from the intestines of aphids. the peculiar life-cycle in which successive generations are produced through the summer months by virgin females--the egg developing within the body of the mother--is described at length in the articles aphides and phylloxera. the _coccidae_ have only a single claw to the foot; the males (fig. 12 _a_) have the fore-wings developed and the hind-wings greatly reduced, while in the female wings are totally absent and the body undergoes marked degradation (figs. 12, _e_, 13, _a_, _b_). in the coccids the formation of a protective waxy secretion--present in many genera of homoptera--reaches its most extreme development. in some coccids--the "mealy-bugs" (_dactylopius_, &c.) for example--the secretion forms a white thread-like or plate-like covering which the insect carries about. but in most members of the family, the secretion, united with cast cuticles and excrement, forms a firm "scale," closely attached by its edges to the surface of the plant on which the insect lives, and serving as a shield beneath which the female coccid, with her eggs (fig. 13 _a_) and brood, finds shelter. the male coccid passes through a passive stage (fig. 4) before attaining the perfect condition. many scale-insects are among the most serious of pests, but various species have been utilized by man for the production of wax (lac) and red dye (cochineal). see economic entomology, scale-insect.