=Hemiptera: the sucking-bugs.=--TECHNICAL NOTE.--Obtain specimens of water-striders (narrow elongate-bodied insects with long spider-like legs which run quickly about on the surface of ponds or quiet pools in streams), water-boatmen (mottled grayish insects about half an inch long which swim and dive about in ponds and stream-pools), back-swimmers (which are usually in company with the water-boatmen, but which swim with back downwards and are marked with purplish-black and creamy white patches), cicadas (the dog-day locusts), and plant-lice (the "green fly" of rose-bushes and other cultivated plants). Compare the external structure of some of these Hemiptera with the other insects already examined; note especially the sucking beak, composed of the elongate tube-like labium in which lie the greatly modified flexible needle-like maxillæ and mandibles, the whole forming an equipment for piercing and sucking. Obtain immature specimens of some of these insects (distinguished by their smaller size and the wing-pads); note that the metamorphosis is incomplete, the young resembling the parents in general appearance. Both immature and adult specimens of water-boatmen (_Corisa_), back-swimmers (_Notonecta_), and water-striders (_Hygrotrechus_) can be easily kept in the laboratory aquaria- and their swimming, breathing, and feeding habits observed. Note especially the carrying of air down beneath the water. [Illustration: FIG. 62.--The female red orange scale insect, _Aspidiotus aurantii_, very injurious to orange-trees. It has no wings, legs, nor eyes, but remains motionless on a leaf, stem, or fruit, holding fast by its long slender beak, through which it sucks up the plant-sap. The male is winged, and has no mouth-parts, taking no food. (Photo-micrograph by Geo. O. Mitchell.)] [Illustration: FIG. 63.--The female rose-scale, _Diaspis rosæ_, a pest of rose-bushes, without eyes, wings, or legs, but with slender sucking proboscis. The male is winged and without mouth-parts. (Photo-micrograph by Geo. O. Mitchell.)]