1920] Richmond, Studies on the Biology of the Aquatic Hydrophilidoe 75 



Egg-case. — Eggs are covered only with loosely applied silk and each measures 

 0.54 mm. in length and 0.027 mm. in width. 



Xewly Hatched Larva. — Length, 1.13 mm.; width, 0.288 mm. Whitish, 

 except chitinized portions which are brownish; integument, including thoracic 

 sclerites, dotted with minute setae. 



Head quadrangular, very slightly elevated; fronto-clypeal suture weakly in- 

 dicated, more prominent at the sides; frontal sutures converging strongly caudally 

 as far as the middle of the head, then slightly diverging to the posterior margin of the 

 head; and united by a transverse suture which runs along the hind margin of the 

 head so close that it is hardly noticeable; epicranial suture absent and the postfronto- 

 vertical-sclerites widely separated; gula reduced, pentagonal, with its sides concave, 

 especially the latero-anterior ones; the anterior angles acute; gula sutures prominent 

 and confluent; two, small, oval, cervical sclerites present. 



Labro-clypeus tridentate, the outer two teeth bifid, with a row of four seta?, 

 each of which is located between the five teeth. Left frontal angle slightly less promi- 

 nent and less advanced than the right, which is nearly in line with the anterior margin 

 of the labro-clypeus. Both angles rounded and bearing a few short setae. Epipharynx 

 spinous. * 



Ocular areas roundish ; in groups of six and indistinct ; arranged somewhat in a 

 circle. 



Antennae fairly short, barely exceeding the distal inner tooth of the mandible; 

 first segment a little wider and longer than the second and slightly indented on the 

 inner side; second segment swollen and bearing a colorless, finger-like appendage, in 

 addition to the sense-cones at the latter 's base; third segment about the same length 

 as the appendage of the second segment, two-thirds as long and half as wide as the 

 second segment, and bearing several sense-cones and a prominent terminal seta. 



Mandibles symmetrical, prominent, sharply pointed at their tips and with two 

 strong inner teeth; serrations on the inner surface of the tip as well as on the inner 

 surfaces of the inner two teeth but indistinct, those on the left mandible more promi- 

 nent; molar areas smooth. 



Maxillae with joint-like palpifer; stipes large, swollen, very slightly narrowed 

 towards the apex, much shorter than the palpifer and palpus together, with a stout 

 inner disto-lateral seta (there may be a row but it was not observed) and a number of 

 small, stout dorsal setae mounted on tubercles; palpifer large, a little wider than long, 

 bearing a single, stout, inner lateral seta near its base and a rudimentary lobe, pos- 

 sessing several short, apical setae, besides a single longer seta ; palpus slightly narrowed 

 towards the apex, all segments about the same length; first segment nearly three 

 times the length of the rudimentary lobe of the palpifer; the terminal segment with a 

 group of sense-cones at its extremity; articulating maxillary piece well developed. 



Labium slightly exceeding the distal inner tooth of the mandible; submentum 

 very small; mentum subcordiform, narrower and shorter than the palpiger, which is 

 broadened distally and bears a seta on each side of the median line near the anterior 

 margin; palpus with second segment more slender, one and a half times as long as 

 the first segment and possessing sense-cones at its extremity; ligula nearly as long as 

 the palpus, apparently two-segmented, the first segment nearly as long as the first 

 segment of the palpus 



