Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/162

150 INSECTS ciadic, and Sayriilx) belong to the Eupoda, and include the well- known Asparagus Beetle (Crioccris aspararji), tlie genus Donacia (and allies), which is aquatic in its earlier stages, and the brilliant exotic genus Sagra (remarkable for its enormously thickened hind femora), the larva of which forms galls on the stems of plants and lives therein. Cryptocephalidss (including Clythridie) are remark- able for the habits of the larva}, which form hard cases of excrement (?) in which they live. Chrysomelidse are a group of often beautiful insects, mostly remarkable for their nearly hemispherical form; they include, inter alia, 2 imarcha (the Bloody-nosed Beetle), the well- known genus C/irysomcla,and the Colorado Potato-Beetle (Doryplwra or Longitarsus) ; most of them distil an acrid fluid ; the larva; are short and obese, feeding exposed and the pupae often have the remarkable peculiarity of being suspended by the tail. Ifalticidse are noted for their thickened hind femora and their jumping powers ; though small in size, some of the members (e.g. , the Turnip- Flea) are most destructive. Cassididas (or Tortoise-Beetles) usually have the sides of the elytra expanded ; the larvae have the very singular habit of concealing themselves under a covering formed of their own excre ment, which is sustained by means of a forked appendage at the ex tremity of the body. Other families (such as Hispidse, and Galeru- cidze) must be passed over. The last division of the Tctramera is the Clavipalpi, often placed with the Trimcra, and forming a con necting link therewith. They are a small group, with the last three joints of the antennae forming a compressed club, and the last joint of the maxillary palpi also broadly clavate. The family Erotylidx mainly constitutes the group ; the larva: probably all live upon fungi. In proof of the wide divergence of opinion as to the re lationship of special groups, it may be mentioned that one author places certain genera of this group amongst the Clavicornia of the Pentamerous division. The last of the great divisions of Colcoptcra forms the Trimera. As in the Tetramcra, it was discovered that the term is not strictly applicable, and that a minute joint is concealed between the lobes of the second joint of the tarsi, hence they have been called Pscudo- Trimcra and Crypto- Trimcra. Some authors have made this group a place of refuge for many almost isolated forms, the natural position of which it is difficult to suggest. At present, however, only a small number of more homogeneous materials are usually located here, and these are divided into Aphidiphaga and Fungicola. The Aphidiphaga comprise the familiar Lady- Birds (Coccinclla) and allies; these have the last joint of the maxillary palpi hatchet-shaped, have short-clubbed antennae, and have the body remarkably hemi spherical. They appear to feed chiefly on other small insects in both larval and perfect stages, and aphides are especial articles of diet with them ; but the writer has seen a larva of Coccinella with its head deeply immersed in the juicy body of a recently formed pupa of its own species. Fungicola have the last joint of the maxillary palpi filiform, with longer antennae, and, as a rule, less hemi spherical body. They contain a number of mostly small and little familiar forms, and, as their name indicates, are often found in fungi, on which they no doubt principally subsist. DIPTERA. Only the anterior (mesothoracic) wings pre sent, membranous, usually naked, with varying longitudinal nervures and but few transverse nervules. Posterior wings replaced by knobbed filaments termed "halteres." Mouth consisting of a rostrum formed chiefly by the extended labium, forming a canal in which the other usual organs, modified into lancet-shaped pieces, are contained, the whole forming a sucker ; only the maxillary palpi developed. Thorax consisting almost entirely of the greatly enlarged mesothorax, the two other divisions very small, and scarcely separable from the mesothorax. Tarsi 5-jointed ; the end joint with a pair of more or less disciform pulvilli. Meta morphosis complete. Although it is the generally received opinion that the halteres are the representatives of the posterior wings, there have been those who regard them rather as connected with respiration or hearing, and by some they have even been considered as belonging to the base of the abdomen rather than to the thorax ; this latter idea results from the diffi culty of defining the true limits of the metathorax. At the base of each anterior wing is a small membranous portion termed an " alulet," not absolutely connected with the wing itself, but which must be considered an adjunct, and certainly not representing a posterior wing. Diptera form one of the most extensive orders. The Genuina are commonly divided into two great groups, according to the structure of the antennae, and termed Nemocera and Brachycera respectively ; but it has long been seen that these divisions are not natural, especially with regard to metamorphoses, and Jkaucr proposed division according to whether the larval skin at the last moult opens by a slit down the back or in a curvilinear manner, a proposal he has since extended by demonstrating that those two divisions Orthorhapha and Cyclnrhapha are rendered the more natural by the pupal condition being correlated with differences in the larva and perfect insect, and eventually it is probable his views will be generally adopted. Another basis for division is according to whether the pupa is free (sometimes active, but not taking nutriment) or enclosed within the hardened skin of the larva ("obtected" or " coarctate "). The division into Nemocera and Brachycera is here followed. In the Nemocera the antennae are long and slendcr,and composed of a considerable number of small joints, which are often verticillato or plumose. They include the families Culicidse, Chironomidfc, Psychodidx, Cecidomyiidas, Mycctophilidaz, Tipulidie, and Bilio- nidse, but some authors make a more minute subdivision. All these, and a multitude of others, fall into Brauer s suborder OrthorhapJm,o.i(. the pupa is obtected. Here come some of the most familiar and bloodthirsty members of the order, such as Gnats (or Mos- quitos), Midges, Gall-Midges, "Daddy Long Legs," &c. , and some of them cause incalculable mischief to the agriculturist. In those species in which the earlier stages are aquatic, the pupa is active. The Brachycera have the antenna} short and thick, not more than three-jointed, but the terminal joint has a bristle (arista) which is sometimes articulate. These again have been divided into llcxa- chastiB, Tctraclixtaz, and Dichietie, according to the number of seta} concealed in the mouth. They are "cyclorhaphous," and the pupa is coarctate. It is not possible to enumerate here all the families, nor to allude to the extreme diversity of habit and structure that exists. House-Flies, Blow-Flies, Flesh-Flies, Bot-Flies, and Gad-Flies, the beautiful Syrphidse (many of which devour aphides in the larval state), the parasitic Tachinas, the plant-eating Fhytomyzw, &c., all belong to this division. The Pupipara are a small group distinguished especially by the fact that the larvae and pupa? are developed in the body of the mother, and the head is sunk in the thorax ; they have even been considered a distinct order termed Homaloptera. All are parasitic. They include Omithomyia (Bird-Flies), Mclopliagus (the Sheep- Tk k), the extraordinary wingless genus Nycteribia, parasitic upon bats, and the perhaps still more extraordinary genus firaula, a minute creature known as the Bee-Louse. Brauer terms them C yclorhapha pupipara. With the Diptera (as a distinct section) it is now the all but universal practice to include the Aphaniptera or Fleas, at one time considered as forming a distinct order. They differ from true Diptera in their laterally compressed form, well-defined thoracic divisions, absence of wings (which are represented only by scales), aborted antennae, developed labial palpi, &c. The month of the imago is (as is too well known) formed for suction, and its parts can be homologizecl with those of the true Diptera. The larva is slender and worm-like, and is mandibulatc, in all probability feeding on the scaly debris or scurf from the skins of the animals attacked; it is not found on the animals themselves, but in their beds or other resting-places. The pupa is inactive. For all practical purposes the Aplwniptera include only two genera Pulex and Sarcopsylla, the Flea and the Chigoe or Jigger. Many mammals and some birds have each its own peculiar species of ilea, or more than one, and the size of the tormentor is often in an inverse proportion to that of the tormented, the ilea of the mouse being of gigantic pro portions. The chigoe is notorious in tropical America for its habit of penetrating the skin of man, especially on the feet, the abdomen of the insect swelling and causing troublesome ulcers. Formerly it was believed that the eggs were deposited in the ulcers and that the larva? fed therein, but more recent observations tend to prove that the habits are much those of ordinary fleas. LEPIDOPTERA. Four membranous wings (frequently rudimentary, or sometimes wanting, in the female) clothed with flattened striated scales ; neuration open ; transverse nervules few ; at the base of the anterior margin of the posterior pair is frequently a bristle used for connecting the two pairs in flight. Mouth haustellate, the maxilla) being much elongated and very slender, forming two closely- applied pieces, which together make the suctorial apparatus by means of which the nectar of flowers is pumped up for food ; in some groups this apparatus if? rudimentary. Labinl palpi strongly developed, the maxillary ordinarily rudimentary (but more developed than the other pair in a