1920] Richmond, Studies on the Biology of the Aquatic Hydrophiliclce 37 



segment ; latter still more slender, a little stouter than the second and with several 

 distal seta? in addition to a small, two-segmented, finger-like appendage. 1 



Mandibles asymmetrical, prominent, elongate, sharply pointed at their tips, 

 each mandible with two- inner toothed areas; the distal inner tooth on each well 

 developed, bifid, their anterior margin minutely serrate, and their inner surface 

 with a groove, which extends to the base of the mandibles; this latter groove sep- 

 arates the proximal inner tooth of each mandible into two, equal, flat teeth; those 

 on the left mandible are much larger than those on the right and with a curved edge, 

 which crosses the groove, slightly proximal to them. 



Maxillae with joint-like palpifer; cardo 3 small; stipes slender, swollen at the base, 

 slightly constricted in the middle, longer than the palpifer and palpus together and 

 its inner surface with a row of five setse; palpifer only slightly narrower than stipes 

 but less than one-fourth its length; a chitinous finger-like appendage at its interno- 

 distal angle bearing a long seta and a microscopic lobe or sense-cone apically; palpus 

 tapering and curving in slightly; the first segment small; the second about as long 

 as the palpifer; the third a little longer than the latter and with terminal sense-cones. 



Labium prominent, the palpus nearly attaining the distal end of the stipes, its 

 first segment short, the second of the same width but much longer and with terminal 

 sense-cones and setse; ligula well developed, more than twice as long as the first palpal 

 segment, cylindrical, only slightly tapering; palpiger a little longer than wide, 

 slightly swollen; mentum subcordiform, anterior angles pronounced and sharply 

 pointed; dorsal surface with numerous minute spines at its basal half; submentum 

 extremely transverse and joint-like. 



Prothorax nearly as wide as the head, angles slightly rounded; pronotum 

 entirely chitinized except at the anterior and posterior margin and possessing a few 

 scattered setse besides a transverse row of six setse in front and a transverse row of 

 four in back; a large ventral sclerite present in front of the prothoracic legs. Sagittal 

 line continuous throughout the thorax. Pro-mesotergal sclerites are present and are 

 small, elongate and horizontal. 



Mesothorax much shorter than the prothorax, about the same width and with a 

 pair of fairly large, irregular, sclerites, each with a prominent seta caudally. Spira- 

 cular area with three small tubercles. A rudimentary bifore spiracle present in each 

 externo-frontal angle. 



Metathorax similar but slightly narrower and shorter and its sclerites more 

 irregular caudally. A small pleural appendage present. 



Legs more than twice as long as the width of the thorax; segments beginning 

 with coxae bear the relation of 16, 7, 16, 12, and 9; tarsi well developed, claw-like 

 and each with two inner setse, one proximal to the other and smaller. 



Abdomen with eight distinct segments narrowed posteriorly, ninth and tenth 

 rudimentary. The first seven tergites similar, each with two very much reduced, 

 oval, chitinized patches on the prseseutum, the first pair larger than the others, and 

 four small but conspicuous tubercles in a transverse row across the posterior fold of 

 the scutum, each bearing a long, colorless seta. Each tergite consists of three trans- 



'Wickham, 1893, considers this appendage as one-segmented but remarks that it appears to be 

 two-segmented. 



2 Duges, 1883, des iribes T. lateralis as possessing only one inner tooth. The terminal segment of 

 the maxillary palpus i- also small and eone-shaped. 



Wir-kharn, 1 893, said that he r-ould not find the basal segment in his specimen although Duges had 

 apparently observed it in T. lateralis. 



