"A convenient system of classification for the Lepidoptera is based on the structure of the antennae. By it we get two great sections: 1st, Butterflies (RHOPALOCERA); 2d, Moths (HETEROCERA), which latter may again be divided into Crepuscular and Nocturnal Moths. Butterflies are at once distinguished from moths by their antennae being straight, stiff and _knobbed_, and by being day-fliers or diurnal; while moths have the antennae tapering to a point, and are, for the most part, night-flyers or nocturnal. The crepuscular moths, composed mostly of the Sphinges or Hawk-moths, hover over flowers at eve, and connect the two sections not only in habit, but in the character of the antennae which first thicken toward the end, and then suddenly terminate in a point or hook. [Illustration: FIG. 17.--A Clothes-moth (_Tinea pellionella_)--enlarged. _a_, adult; _b_, larva; _c_, larva in case.] "Order HEMIPTERA ([Greek: hemi], half; [Greek: pteron], wing), Bugs. The insects of this order are naturally separated into two great sections; 1st, Half-winged Bugs, or HETEROPTERA ([Greek: heteros], different; [Greek: pteron], wing) having the basal half of the front wings (called _hemelytra_) coriaceous or leathery, while the apical part is membranous. The wings cross flatly over the back when at rest; 2d, Whole-winged Bugs, or HOMOPTERA ([Greek: homos], equal; [Greek: pteron], wing), having all four wings of a uniform membranous nature and folding straight down the back when at rest. The latter, if separated, may be looked upon as a Suborder. [Illustration: FIG. 18.--A Plant-bug (_Euschistus punctipes_).] "Transformations incomplete; _i. e._, the larvae and pupae have more or less the image of the perfect insect, and differ little from it except in lacking wings. [Illustration: FIG. 19.--A Soldier-bug (_Milyas cinctus_). _b_, beak enlarged.] "The genuine or half-winged Bugs (Figs. 18 and 19) are usually flattened in form, when mature; though more rounded in the adolescent stages. They may be divided into Land Bugs (_Aurocorisa_) and Water Bugs (_Hydrocorisa_). The species of the first division very generally possess the power of emitting, when disturbed or alarmed, a nauseous, bed-buggy odor, which comes from a fluid secreted from two pores, situated on the under side of the metathorax. Such well-known insects as the Bed-bug and Chinch-bug belong here. The habits of the species are varied, and while some are beneficial, others are quite injurious to man. [Illustration: FIG. 20.--A Tree-hopper (_Ceresa bubalus_). _a_, side; _b_, top view.]