Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/163

INSECTS 151 few small groups). Protliorax very narrow, with a pair of lateral organs termed jmtagia. Legs slender; tibiae spurred. Metamorphosis complete, all the appendages of the pupa enclosed in common covering with the body, but leaving the parts visible (occasionally, in some of the lower groups, the extremities of the appendages are free). Larva (termed a caterpillar) with six thoracic legs, and with a varying number (never more than 4 pairs) of fleshy abdominal and two anal prolegs (rarely the larva is apodal). With few exceptions, they are phytophagous. These insects are familiarly known as Butterflies and Moths, and the order contains the most beautiful insects that exist, and forms the most popular and attractive of all for collectors. The scales of the wings (and other parts of the insect) are really modified hairs. Each is a flattened sac, striated on OTIC side, containing variously coloured pigments, the arrangement of scales of different colours causing the beautiful markings and patterns so universal ; but metallic colours are due also to interference caused by minute inequalities of the surface, combined with the contained pigment. The classification of Lepidoptera is still in a state of much uncertainty. By collectors they arc fancifully divided into Macro- and Micro- Lepidoptera, A more familiar division is into Butterflies and Moths, the former being termed Rlwpalocera (or Diurni}, the latter Hetero- cera (or Nocturni). The Rhopalocera are especially distinguished by their clubbed antemiic. Tho following great groups are tolerably well marked (but each has been much subdivided) : viz., Papilionidaz, Nym- phalidse, Erycinidae., Lycosnidic, and Ilesperiidse. Some split the division into two, according as the pupa is suspended by the tail only, or has a thread round the body as well (these groups are termed Suspcnsi and Succincti respectively) ; the NymphcdidiK are especially characteristic of the first of these. In the Nymplialidte the anterior legs arc not fully developed in either sex ; in the Erycinidse, and Lycsenidie this occurs only in the males. The Jfcsperiidie have the club of the antenna; terminated by a hook, and the position of the wings in repose dilFers ordinarily from that in the other groups; the pupa is enclosed in a rudimentary cocoon, and may even be subterranean. The Heterocera are subdivided roughly into Spliincjidse, Bomly- cidae, Noctuidce, Gcomctridte, Pyralidse, Tortricidw, Tincidx, and Ptcrophoridce ; but much more minute subdivision is adopted by specialists. In these the form of the antennae is very variable (as the name implies), and the bristle on the posterior wings is usually (not always) present. The Sphinqidie (which comprise some of the largest and most robust moths) usually have the antenna; fusiform towards the tips. JBombycidai generally have the antenna; of the male strongly pectinate, and those of the female simple or nearly so ; the larva? with four pairs of abdominal prolegs (and the anal pair); but this is a group of extremely heterogeneous materials, if taken in its widest sense ; it includes the Silk- Worm Moths as familiar examples, and many extraordinary forms, amongst which may be mentioned the curious PsycltidtK, in which the larva; manu facture portable cases wherein they live, and in which the females are apterous. Perhaps allied to this group, or intermediate between it and the Sphingidie, is the curious and abnormal collection of pretty insects termed Castniada ,, at one time considered to be butterflies, and even yet included with them by some authors. The haustellum is rudimentary in the true Uombyddie. The Noduidx are stout-bodied moths, mostly (but by no means always) of nocturnal habits ; the antenna; greatly varying, but not thickened ; the bristle on the posterior wings present ; the hau stellum present (in one genus, Opliidcrcs, it is strong enough to pierce the skin of oranges). Theyare mostly divided into two groups accord ing to the number of the prolegs in the larvae (four, or only three, abdominal pairs), and the neuration of the posterior wings. The larvae are iisually nearly smooth (those groups with hairy larva; are by some transferred to the Bombycidae), and the pupa; subter ranean. Geometridse are especially distinguished by the presence of usually only one pair of abdominal prolegs, occasioning a peculiar form of locomotion, termed " looping" ; antenna; varying ; bristle of posterior wings present ; the wings usually expanded when at rest. With apparent relations to these is the small group Uraniidse, consisting of beautiful papilioniform insects, still by some placed with the butterflies. Pyralidse form a special group of varying, and for the most part rather small, insects, with simple (or nearly simple) antenna; ; long slender legs ; the bristle of the posterior wings present ; long palpi ; lai v;c with three to five pairs of abdominal prolegs, and mostly smooth and glossy in appearance. Torlriddas are small insects of nocturniform mien when at rest (the wings being horizontal and not expanded) ; antenna; simple ; bristle of posterior wings absent ; haustellum short ; palpi short ; larva; with four pairs of abdominal prolegs. Many of the species of this group do immense damage to trees and garden plants. The Tineidae is an immense group of mostly small (often very minute) insects, with extremely varying structure and habits. They may always be distinguished from the Tortricidx, by the long palpi (the maxillary pair being sometimes strongly developed and exceeding the labial) ; the fringes of the wings are usually very long. Some of these minute forms are excessively beautiful. The group as a whole is made up of very incongruous materials. Ptcrophoridse are a small group at once distinguished by the wings being split up into linear divisions, hence they have been termed "plumes." By some they are not considered distinct from the Pyralidic, with which there is considerable structural affinity. NEUROPTEKA. Four membranous and for the most part densely reticulate wings, more or less clothed with hairs, but without true scales ; very frequently the hairs are on the neuration only. Mouth mandibulate. Metamor phosis complete, but the pupa has its members free. In the outline of classification (at p. 147) proposed to be adopted in this article, it is stated that the Neuroptera. as there indicated are considered as forming a single order, more as a matter of convenience than from any conviction of the homogeneity of the two divisions. The Trichoptera (or Caddis-Flies) form a very natural and sharply defined group distinguished by their rudimentary mouth-parts, with the exception of the two pairs of palpi, which are strongly developed, the maxillary pair being the longer, and with often the greater number of joints ; the antenna; setaceous; wings with com paratively simple neuration and but few transverse nervules, ordi narily covered with hair (which sometimes simulates scales) ; larva; (known as Caddis- Worms) with well-developed thoracic legs, and anal crotchets, but without prolegs, living in tubes covered with extraneous materials ; pupa lying free in the case, or occasionally in a special cocoon, only active just before its metamorphosis ; habits (with one or two exceptions) aquatic. It is considered by the writer that there is direct relationship of the Trichoptera with the Lepidoptera, and this idea acts as the key to the scheme of classification adopted. They are divided into seven families, viz., Phryganeidos, Limnopliilidse, Scricostomatidw, LcptoccridiK, Ilydropsycliidae,, Rhyacophilidas, and Hydroptilidx,, chiefly according to the structure of the maxillary palpi. In the PJiyacopliilidx and Hydropsychidse the larva; inhabit fixed cases, in the others the cases are free, and caried about by the inmates ; in the llliyacopliilidie, the pupa is enveloped in a special cocoon. The neuration shows strongly-marked homology with that of Lepidoptera. The Planipennia (or true Neuroptcra according to modern ideas) have strongly-developed mandibulate mouths ; for the most part moniliform or filiform (often clavate) antennae; the wings ordinarily densely reticulate, with very numerous transverse nervules, the membrane hairless or nearly so. The larva is more divergent from the Lepidoptcrous type. The pupa is ordinarily in a cocoon ; it is active just before its transformation. A convenient subdivision is into Panorpulee,, SiaUdse, and Mc(jaloptcra. The PanorpidiB (Scorpion -Flies, &c.) arc remarkable for the mandibles, &c., being situated at the end of a long beak, formed by the much-elongated clypeus above and the lower lip beneath. The wings have open reticulation, and the larva is more vermiform than in the succeeding groups, so that the relationship to the Tricho ptera is close. They are carnivorous both in imago and larva, and the latter is subterranean. Paiwrpa is remarkable for the cheliform termination of the abdomen, Bittacus for its tipuliform aspect, Jjorcus for its nearly apterous condition. The Sialidse form a heterogeneous group of small subdivisions with setaceous antenna; (which are sometimes pectinate) ; strongly developed prothorax; the third or fourth joints of the tarsi cordate. They are again divided into two sections (or families), of which PJiapMdia and Sialis may be taken as the types. The former (Snake-Flies) are especially remarkable for the enormously elon gated prothorax (the anterior legs at its posterior extremity) ; the larva; sub-cortical. The latter comprise mostly large insects with strong (but not greatly elongated) prothorax and ample wings, the larvae of which are aquatic, and provided with lateral branchial plates ; the genus Corydalis is remarkable for the enormously elongated mandibles of the male (but not in all species). Mcgaloptcra contain many groups of insects, with mostly monili form (or clavate) antenna;; densely reticulate broad wings; varying prothorax ; tarsal joints not dilated. The number of subfamilies is large. The most prominent forms are the ifantispidee, with their long prothorax (the anterior legs at its anterior end), the larva: of