THE SMALLER WATER STRIDERS. 995 



"It is a very attractive object when seen upon the surface of a quiet 

 brook, where it runs over the water film with astonishing rapidity, not 

 with the rowing impulses of a Gerris, but standing well up and moving 

 all the legs in steady succession. In the Middle States they hibernate in 

 colonies beneath the overhanging banks of the smaller streams. Only in 

 warm sheltered situations do they pass to the full completion of the 

 winged adult stage, and in the colder parts of the country, as in Maine 

 and lower Canada, they seem to be always unwinged." 



Bueno (1923, 420) states that: "The young, after five molts, 

 reach the adult stage in some six weeks. As breeding begins 

 about April, there may be as many as four or five broods before 

 the end of October. It seems to prefer the sloping banks of 

 sluggish streams or ponds, or to perch on partly submerged 

 sticks, or on the sides of springs or water holes in the outgrow- 

 ing mosses. It is pre-eminently predaceous and will attack in 

 force any insects struggling in the water." 



II. Rhagovelia Mayr., 1865, 445. 



Robust species of medium size for the family, readily dis- 

 tinguished by the 1-jointed front tarsi and the long, deeply 

 cleft terminal joint of the second pair. In this cleft there is a 

 row of long ciliated hairs arising from a common base. When 

 the insect moves on the surface of the water these are extended 

 fan-like, but in repose are folded back within the fissure. They 

 have the head short, blunt, wider across eyes than front margin 

 of pronotum ; antennae rather stout, the basal joints with erect 

 bristly hairs, joint 1 longest, slightly curved, about two-thirds 

 longer than 2 ; 2 and 3 subequal, 4 usually slightly shorter than 

 3. Pronotum variable as to species; elytra usually wanting; 

 basal joint of middle tarsi very short or wanting. Male of 

 wingless form with hind margin of pronotum broadly rounded 

 or subangulate; abdomen apically much narrowed, the con- 

 nexivum strongly subvertically reflexed. Female of wingless 

 form with hind margin of pronotum either subtruncate or pro- 

 longed as a blunt spine ; connexiva usually reflexed against part 

 of the dorsal surface of abdomen. 



Of the function of the tuft of hairs in the slit of middle 

 tarsus Bueno (1907a, 63) states: "The middle tarsus is in con- 

 tact with the water along its entire length, with the slit ver- 

 tical to the surface. When in this position the spread tuft of 

 hairs projects beneath into the water and is a powerful 

 auxiliary in swimming." Five species are known from the 



