1920] Richmond, Studies on the Biology of the Aquatic Hydrophilidce 45 



stomal margin prominent and there is a furrow in front of it but the labrum and 

 maxilla? are united at the anterior margin; gula reduced; the gular sutures fairly 

 prominent and confluent and its anterior margin with two long seta? on each side of 

 its median line. The cervical sclerites present. 



Labro-clypeus asymmetrical, irregularly toothed in the middle with three teeth 

 and with two, prominent, blunt setse projecting from the ventral side. Lateral 

 expansions of epistoma differing greatly; the right rounded, overlapping the base of 

 the right mandible; the left overlapping the left mandible and rounded but bearing 

 a row of stout seta? which become shorter toward the median line (five or six are very 

 prominent). 



Ocular areas in groups of six but rather indistinct. They are arranged in two 

 parallel rows, the outer one of the posterior row a little out of line and more anterior. 



Antenna? fairly stout ; the first segment about two-thirds as long as the second, 

 slightly constricted in the middle and bearing at least two dorsal sensory pits; second 

 swollen a little and bearing a small, colorless, finger-like antennal appendage in addi- 

 tion to the sense-cones at the latter's base, and a long inner seta, arising from a 

 tubercle, as well as a few less prominent ones; third segment very small, almost as 

 wide as long, a little longer than the appendage of the second segment, and bearing 

 three long seta? and several sense-cones at its extremity. 



Mandibles asymmetrical, fairly prominent and stout, sharply pointed at their 

 tips, and toothed on the inner side; right mandible bears three inner teeth, decreasing 

 in size from the cephalic to caudal one; the left has two toothed areas on the inner 

 side, both of which present a pectinate region dorsally, in addition to a tooth. 



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

 to apex, longer than the palpifer and palpus together and its inner surface provided 

 with short, stiff seta?, and several longer stout seta? at intervals; the more slender 

 setse are present at the externo-distal angle; palpifer small, a little wider than long, 

 bearing an inner rudimentary lobe, possessing a seta and sense-cones, below which is 

 a slender seta; palpus with first segment about one-half the second while the 

 third is a little longer than the first two and more slender and more cylindrical; the 

 terminal segment possesses a group of sense-cones at its tip; articulating piece of 

 maxilla well developed. 



Labium small and with only its palpi exceeding the labro-clypeus; mentum 

 and palpiger very small; both segments of the palpus are cylindrical, the 

 second about three times as long as the first, more slender and with its tip possessing 

 a number of sense-cones; ligula absent; palpiger has two seta? on its anterior border 

 near the median fine ; submentum very indistinct. 



Prothorax very slightly narrowed in front, larger than the head; pronotum 

 entirely chitinized, except the sagittal line, with a transverse row of seta? (about ten) 

 just a little posterior to the cephalic margin, several others on the sides. Meso- and 

 metathorax a little wider and shorter than the prothorax. Mesoscutum and meta- 

 gcutum both represented by two subtriangular and very much reduced sclerites, each 

 having a seta in their caudo-medial angle. The mesonotum has two smaller oval 

 sclerites 1 just lateral of the median line and posterior to the cephalic margin. The 

 spiracle at the tip of a little conical tubercle 2 in each antero-lateral angle of the meso- 

 thorax two-fifths as long as the thorax is wide. 



'Probably homologous with the cervical sclerites. 

 -Trarheo-brancbies of d'Orchvmont. 



