1920] Richmond, Studies 012 the Biology of the Aquatic Hydrophilidoe 25 



As with Ochthebius, only one egg is deposited at a time. Eggs 

 were laid in an aquarium during the middle and latter part of April. 1 

 They were placed on a leaf which rested on a stone, some in the water 

 and some out but always in a damp situation. Each egg was kept in 

 position by a blanket-like covering of closely applied silk which exceeded 

 the egg on all sides and showed its form. The eggs hatch in six to eight 

 days, emerging through a narrow, longitudinal slit in the upper side of 

 the egg-case. The larva? are very rapid walkers and closely resemble 

 those of Ochthebius, almost seeming to glide over the surface of the stones 

 when stimulated. The}' are clearly non-aquatic in their movements, 

 becoming quite helpless when below the surface film. 



Egg. — Length, 0.591 mm.; width, 0.242 mm. The flare-like margin exceeds the 

 egg itself about 0.09415 mm. all around and is entire, being only slightly irregular. 



Xewly Hatched Larva. — Length, 1.29 mm.; width, 0.242 mm. Whitish 

 except chitinized regions which soon become brown; integument with many incon- 

 spicuous setulse as well as regularly arranged setae which are fairly long, stiff and 

 brownish. 



Head strongly rounded, globular ; f ronto-clypeal suture weakly indicated, except 

 at the sides; frontal sutures, converging, unite behind the middle of the head to 

 form the epicranial suture, the whole presenting a Y-shaped appearance; gula small, 

 constricted laterally, and its posterior angles extend to form long, lateral arms; 

 cervical sclerites, if present, not noticeable. 



Clypeus fairly distinct, transverse, slightly arched, wider than the labrum and 

 with a transverse row of sLx equidistant seta? on the posterior half. 



Labrum somewhat semicircular with four setse on each side, the anterior one 

 prominently branched (almost pectinate) while the third pair are strongly bent in- 

 ward and tapering; anterior margin slightly emarginate with a short, finger-like 

 appendage on each side, with a seta just behind but a little lateral; four other setse 

 on the upper side of the labrum; two near the middle and two on the posterior half 

 but more widely separated. The lateral expansions of the epistoma are not prominent. 



Epipharynx apparently not spinous. 



Ocular areas round, five on .each side, not aggregated; the first and second close 

 together and placed one above the other just behind the gena 2 and below the base of 

 the antenna; the third and fourth closely approximated, widely separated from the 

 latter, and more dorsal; the fifth near the lateral margin of the head and distant 

 from the fifth. 



Antenna? fairly long, barely exceeding the mandibles; first segment about as 

 wide as long and two-fifths the second segment in length; latter more slender with 

 two swellings on the inner side, one at the middle, bearing a long seta and one near 

 the distal end bearing a finger-like appendage besides a long seta; two seta just below 

 the externo-frontal angle; third segment slender, longer than the finger-like appen- 

 dage and more than one-half as long as the second with a seta arising from an inner 

 tubercle near the middle and several terminal setae mounted on tubercles. 



'Many adults were taken in copulo out of doors at this season. 



2 The solerite called the gena may open some question but it evidently corresponds in position to it. 



