250 NATURAL HISTORY OF ARTHROPODS. 



always a free, large segment, bearing the same relations to the other segments as we 

 see in the Coleoptera, and, like them, having a distinctly segmented scutellum. There 

 are usually two ocelli, never three, situated on the vertex, but these are absent from a 

 few genera, and also from the young stages of all. A marked difference in the depth 

 of the body is to be observed in the various groups. Some, such as the Scutelleridas, 

 have the greatest convexity of the surface above ; others, like the Coreidae, are most 

 convex beneath. Numerous intermediate modifications of these surfaces occur, carry- 

 ing with them others which affect the parts of the segments, and of the organs con- 

 nected with them. Examples of each of these will be brought to view as the genera 

 are taken up, and some of the more remarkable forms will be described. 



The group at large is divided into two great sections, based upon modifications of 

 the antenna? dependent upon the habits and kind of element in which the creatures 

 live. Lowest and first of these appear the aquatic kinds, composing the section 

 CRYPTOCERATA, so called from the nearly concealed position of the antenna?, 

 which are short, and placed underneath the head in a cavity near the eyes. 



The family CORISID^E is the most aberrant of the order, being composed of insects 

 whose mouth is flattened out, shortened, directed obliquely backward beneath, and the 

 rostral setae are thrust through a little hole above the actual end of the clypeus, and 

 not as usual at the tip. Instead of being let into the end of the prothorax, the head 

 overlaps and fits intimately against it, and the fore-tarsi, called palae, are flattened 

 like the blade of a pen-knife, are set with bristles on the inner thin edge, similar to a 

 comb, and end in a slender nail at the tip. A most striking feature also appears in 

 the males of Corisa, where the serial parallelism of the ventral segments is disturbed, 

 and on one side broken into pieces as if by explosion. 



This very comprehensive genus includes the greater part of the family, and is com- 

 posed of insects having a long elliptical form, with the front end widest and bluntly 

 rounded. The sides are generally parallel, not much curved, and the membrane is 

 almost of the same texture as the corium ; the head covers the whole fore end of the 

 prothorax like a broad crescentic mask, and the face is carried downward in a wide, 

 nearly flat, blunt triangle, the clypeal part of which is crossed by sutures, marking off 

 the transverse rostral joints. On the under side only one suture is conspicuous in the 

 clypeal region, which gives the apical segment a valvate form, like the labium of a 

 mandibulate insect. Nevertheless, the gular middle line is swollen, and, by close 

 examination is seen to be composed of four joints. The prothorax extends back and hides 

 the scutellum. The antennas are moderately long, tapering towards the tip, and com- 

 posed of four joints, of which the third is longest, more or less thickened at the outer 

 end, while the fourth is almost setaceous, and terminated by bristly hairs. A marked 

 contrast exists between the middle and front legs in the length of 

 the joints. In the former the femora and tibiae are long and slender, 

 the femora longer than the tibiae and tarsus united, while the pos- 

 terior legs are made about equally long by the lengthening of the 

 tarsus, which is a flat paddle composed of two joints, closely re- 

 sembling the same organ of a crab. Our largest North American 

 FIG. 314^- Corisa species is Corisa interrupta. It is one of the moderately broad 

 rupta. forms, dark brown above, tile yellow beneath and on the face and 



legs. The prothorax is polished, minutely engraved punctate, crossed by nine 

 or ten yellow narrow lines, blunt behind, and margined with yellow. The clavus 



