HEMIPTERA. 193 



the mesothorax is scale-like, narrowed, rounded, and depressed 

 around the tip. Behind this, the abdomen tapers more or less to- 

 wards the last segment, which is usually armed each side with a 

 tooth-like process. The under side of the body is generally min- 

 utely pubescent and sericeous like satin, and this is sometimes con- 

 tinued along the sides of the thorax. There are commonly two 

 forms of the adult belonging to the same species, the winged and 

 unwinged. These do not necessarily co-exist. During some years, 

 only the winged forms appear ; while in others, and especially if the 

 spring and summer are cool, the individuals will all be unwinged. 

 Often in sunny, protected places, where the food is abundant, all 

 will be winged, while, in exposed localities, the same species will be 

 found unwinged, with, perchance, a single, more vigorous specimen 

 winged. In some parts of the Southern States three forms occur, 

 those before cited and another which has the wing-covers of scarcely 

 half length." (Uhler.) 



The water-striders prefer quiet waters, upon which they rest, or 

 over which they skim rapidly. They jump from the water to capture 

 flies or other insects for food. Fig. 164 represents a species of Hy- 

 grotrechus. " These insects stow 

 themselves away under the banks 

 of streams, in the mud beneath 

 leaves or rubbish, or at the bottom 

 of water under stones and roots of 

 trees when the autumn begins to 

 be cold ; and from thence they 

 reappear upon the surface of the 

 water as soon as the warm weather 

 of spring returns. Soon after this, 



the eggs are attached by a sort of glue to the leaves and stems 

 of aquatic plants. They are whitish translucent, long, cylindrical, 

 more blunt at the end from which the young emerge than at the 

 somewhat tapering, but round, opposite extremity. If the weather 

 continues to grow warmer, these eggs mature in about two weeks." 

 (Uhler.) 



Five genera occur in our fauna; these can be separate 



following table : * 



A. Body oval, less than three times as long as broad ; pronotum not longer 

 than broad. 



* This table was prepared by Professor H. E. Summers. 



