BUGS. 267 



tracted anteriorly into a neck, the antenna: are mere threads, and the upper surface 

 is often spinous. These are strongly suggestive of certain tropical forms of Reduvids, 

 which they also resemble in the thickened fore-thighs and pattern of coloration. 



Leaving these tenants of the damp soils, we are at once brought into the presence 

 of several families of the Heteroptera, whose habits agree in many particulars, but 

 whose forms are as diverse as their representatives in the perfectly terrestrial groups. 

 These all coincide in living upon the surface of the water, yet, not submerged beneath 

 it, as in the aquatic insects previously considered. 



The first family, HYDROBATID^E, includes insects built upon an elongated pattern, 

 with prominent round eyes, the head inserted in the thorax up to the base of the 

 eyes, and curving forward, from which the stout rostrum bends back to pass between 

 the fore-limbs. Long antennae, of four joints, arise from the prominences, placed 

 some distance in front of the eyes, and the back part of the vertex is depressed. No 

 ocelli are conspicuous, if indeed they are present. The thorax usually widens back- 

 wards, and its thickness is increased by the prominent middle and posterior coxae, 

 which project beyond the sides. No scutellum is apparent, but in its place the end 

 of the dorsal plate of the mesothorax is scale-like, narrowed, rounded, and depressed 

 around the tip. Behind this the abdomen tapers more or less towards the last seg- 

 ment, which is usually armed each side with a tooth-like process. The under side of 

 the body is generally minutely pubescent and sericeous like satin, and this is some- 

 times continued 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 neces- 

 sarily coexist. 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, but with these organs as nicely differentiated into soriimi and membrane as 

 the most completely developed. 



The old name, Gerris, by which many of these insects were formerly known, has 

 become obsolete, by reason of its having been used for various insects not generic-ally 

 connected, so that recently Dr. Stal has been obliged to 

 remodel the family, construct several genera, and place the 

 assemblages of species in newly defined relations. Thus 

 our most common species, G. remit/is, has been taken from 

 Gerris and is now placed in the genus Hygrotrechus. It 

 is a rather large, dark brown, moderately stout species, 

 with the crown of the head, prothorax, and callosities at 

 its end blackish ; the antennae are black, and about as long 

 as the distance from in front of the eyes to the tip of the 

 dorsal piece of the mesothorax ; the first is longer than 

 the next two conjoined; the second and third are short, FlQ . m ._ff ygrotre * chusremigis . 

 of nearly equal length, and the fourth is longer than the 



third. An ochreous line, ending in a hollow space behind, runs along the middle 

 of the prothorax ; the dorsal segment behind this is a little sinuated each side, has a 

 feebly raised, uneven line along the middle, slightly raised lateral edges, and a callous, 

 waved, black seam immediately outside of its lateral margin and running diagonally 



