1320] Richmond, Studies on the Biology of the Aquatic Hydrophilidos # 49 



The case proper measures 1.6 mm. high, 1.2 mm. wide, and 0.323 mm. long. The fila- 

 ment averages about 4.5 mm. long, its width of 0.13 mm. is usually constant and its 

 sides are parallel. 



Xewlt Hatched Larva. — Length, 1.9 mm.; width at its thorax, 0.32 mm. 

 Whitish, with chitinized areas very slightly light yelloAvish. Integument dotted with 

 minute setae. 



Head ovate, elevated; fronto-clypeal suture very indistinct; labro-clypeal 

 suture fairly well indicated; frontal sutures gradually converging as far as the 

 posterior third and then slightly diverging, not uniting to form an epicranial suture; 

 gula reduced, polygonal, posteriorly somewhat rounded ; gular sutures contiguous for 

 a long distance; labium and maxilla inserted at the anterior margin of the head but 

 the signs of the groove are still present and the hypostomal margin distinctly marked 

 off; cervical sclerites present. 



Labro-clypeus small, projecting forward rather prominently, arched, with seven 

 small teeth and four equidistant setae. Lateral expansions of epistoma differ greatly; 

 the right rounded, reduced and not exceeding the labro-clypeus; the left prominent, 

 exceeding the latter, rounded and bearing a row of seta? on its anterior margin. 



Ocular areas in groups of six and closely aggregated, oval, arranged somewhat in 

 a circle, each area equidistant from the other except the sixth area which is about 

 twice the distance from the first area than it is from the fifth. 



Antennae short, not exceeding the mandibles, with their points of insertion widely 

 separated but inside those of the mandibles; first segment a little longer than the 

 second, constricted at its basal half and with a small finger-like appendage, provided 

 with colorless apical setae, at its interno-frontal angle; second segment swollen, only 

 slightly narrowed distally and bearing a small, colorless, finger-like antennal appen- 

 dage, which is nearly as long as the third segment; the latter small, a little longer 

 than wide, and with terminal setae and sense-cones. 



Mandibles asymmetrical, prominent, sickle-shaped, sharply pointed at their tips, 

 and toothed on the inner side; right 1 mandible with two inner teeth, the distal tooth 

 much larger than the proximal one, and the vestige of a third more proximal tooth 

 apparently represented by a minute spine; left mandible slightly notched on the 

 inside towards the tip and with a complicated set of inner teeth, the distal one the 

 largest and triangular; molar area with a small distal, spine-like projection. 



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

 longer than the palpifer and palpus together and its inner surface provided with a row 

 of five, stout, equidistant setae; two slender setae near the externo-distal angle; pal- 

 pifer short, much wider than long, bearing an inner rudimentary lobe, provided with a 

 long seta and a sense-cone, below which is a stout seta; palpus tapering; the first 

 segment only about one-half the palpifer in length; the second much longer and with 

 an externo-distal seta; terminal segment two-sevenths shorter than the latter and 

 with distal sense-cones, in addition to an inner seta. 



Labium small, with only the palpi exceeding the labro-clypeus; submentum 

 small and transverse; mentum transverse with its anterior angles rounded; palpiger 

 rather quadrate, narrower than latter and about the same length, slightly divided 

 anteriorly in the middle and each half bears the two-segmented palpus ; first segment 

 of latter short, the second segment nearly three times as long and with terminal setae; 

 ligula absent. 



>.B. spinosus has a similar right mandible. 



