"The Whole-winged Bugs (Figs. 20 and 21), on the contrary, are all plant-feeders, and with the exception of a few, such as the Cochineal and Lac insects, are injurious. The secretion of a white, or bluish, waxy, or farinose substance from the surface of the body is as characteristic of this section as the nauseous odor is of the first. It forms three natural divisions, arranged according to the number of joints to the tarsi--namely TRIMERA, with three joints; DIMERA, with two joints; and MONOMERA, with one joint to the tarsi." Suborder THYSANOPTERA ([Greek: thysanos], a fringe; [Greek: pteron], wing): This suborder contains the single family _Thripidae_, which comprises minute insects commonly known as Thrips, and of which a common species, _Thrips striatus_, is shown in the accompanying figure. (See Fig. 22.) They bear strong relations to both the Pseudoneuroptera and the Hemiptera and by later writers are generally associated with the latter order. They feed on plants, puncturing and killing the leaves, or on other plant-feeding species of their own class, and are characterized by having narrow wings crossed on the back when at rest, and beautifully fringed, from which latter feature the name of the suborder is derived. [Illustration: FIG. 21.--A Plant-louse (_Schizoneura lanigera_). _a_, infested root; _b_, larva; _c_, winged insect; _d-g_, parts of perfect insect enlarged.] The mouth parts are peculiar in that they are intermediate in form between the sucking beak of Hemiptera and the biting mouth parts of other insects. [Illustration: FIG. 22.--_Thrips striatus_, with wings enlarged at side.] Their eggs resemble those of Hemiptera; the larvae and pupae are active, and in form resemble the adult, except in the absence of wings. Some species, also, are wingless in the adult stage. The pupae are somewhat sluggish and the limbs and wings are enclosed in a thin membrane which is expanded about the feet into bulbous enlargements, giving rise to the name "bladder-footed" (Physopoda) applied to these insects by Burmeister. "Order DIPTERA ([Greek: dis], twice; [Greek: pteron], wing) or Two-winged Flies. The only order having but two wings, the hind pair replaced by a pair of small, slender filaments clubbed at tip, and called halteres, poisers, or balancers. [Illustration: FIG. 23.--A Mosquito (_Culex pipiens_). _a_, adult; _b_, head of same enlarged; _e_, portion of antenna of same; _f_, larva; _g_, pupa. (After Westwood.)] [Illustration: FIG. 24.--A Hawk-fly (_Erax bastardi_). _a_, perfect insect; _b_, pupa; larva shown at side.] [Illustration: FIG. 25.--A Flesh-fly (_Sarcophaga carnaria_, var. _saracenae_). _a_, larva; _b_, puparium; _c_, adult insect with enlarged parts.]