BUGS. 275 







discoidal areoles, but when rubbed these only remain in vestiges, or entirely disappear. 

 It is a very small insect, measuring at most not more than one-tenth of an inch 

 in length, but is a very attractive object when seen upon the surface of a quiet brook, 

 where it runs over the surface with astonishing rapidity, not with the rowing impulses 

 of a LimnotrechuS) but standing well up and moving all the legs in steady succession. 

 The unwinged ones are also rendered conspicuous by spots of white powder, which 

 contrast strongly with the dark brown of the upper side of the abdomen. They 

 hibernate in colonies beneath the overhanging banks of the little streams, in the 

 Middle States, and by the latter part of June have undergone the last change of skin 

 and become fully winged. A large proportion of them, however, do not enter the 

 winged state, but pass through all their changes without gaining even a vestige of 

 the organs of flight. Only in warm, sheltered situations do they pass to the full 

 completion of the adult state, and in the colder parts of the country, as in Maine and 

 Lower Canada, they seem to be always unwinged. Two species also inhabit Europe, 

 and two or three others are natives of the West Indies and Mexico. A genus which 

 might easily be confused with the preceding is Microvelia, which is known in many 

 of the books as Hydroessa. It is composed of very small insects much like the 

 preceding, but the antennae are thicker in the direction of the apex, have six joints, 

 the third and fifth being very minute, and inserted between the longer ones, and there 

 are no ocelli ; the eyes 'are hemispherical, placed next to the pronotum ; the rostrum 

 reaches behind the fore-coxae ; the hemelytra are as long as the abdomen and have six 

 consecutive areoles, of which the basal are smaller than the others, while the apical 

 ones emit two nerves. All the legs are short and rather stout, unarmed, the fore-tarsi 

 are two-jointed, the basal joint very short, the two hind pairs are three-jointed, with 

 the third joint longest and thickest. The nails are situated a little way back of the tip 

 on all the feet. Their general form is short, broad, and deep, with the margin of 

 the connexivum prominently raised. M. pygmcva is a common form in many parts 

 of Europe, and there are undescribed species in the United States and West Indies. 



A strong contrast with the foregoing is seen in the family HYDROMETKID^E. It is 

 composed of dull brown insects of remarkably elongated, almost linear, form, with 

 long legs fitted for walking on the surface of the water. The species inhabit places 

 where weeds and grasses grow in quiet waters, and there they delight to remain at 

 rest, with perhaps a single claw hooked to some projecting object. When disturbed 

 they move very slowly, and seem disposed to save themselves rather by concealment 

 among rubbish or tangled growths than by active movements. The young forms are 

 so very slender that they can only be detected with great difficulty in the places to 

 which they resort. In the adult the head is long, horizontal, almost cylindrical, but 

 with the middle a little narroAved, the tip widened, the basal tubercles of the antennae 

 projecting, and the round eyes placed about midway between the base and tip. The 

 antennae are mere filaments, with the tip of the basal joint enlarged, the second joint 

 longer than the first, the third nearly three times as long as the second, and the fourth 

 about one-half as long as the third. A short, very slender rostrum reaches to beyond 

 the eyes, and has the base placed in a short channel. The thorax is almost cylindrical, 

 a little wider than the tip of the head, but much shorter than the latter. No ocelli 

 are present, and the legs are long, exceedingly slender, and with three-jointed tarsi, 

 at the end of which the minute nails are placed. The wing-covers are narrow, gradu- 

 ally widening behind, generally shorter than the abdomen, bluntly rounded at tip, 

 and furnished with two long nerves, which are connected behind the middle by an 



