188 Journal New York Entomological Society. f^'o'- xx. 



This stage lasts from five to seven days before the larvae begin 

 entering the soil to pupate. In my aquaria the second molt occurred 

 on June 15 and the larvae began entering the soil on June 20. Un- 

 fortunately none of these larvae had pupated when I had to give up 

 the study for other work which called me away. 



The Larval Mouth Parts. — The mouth parts of P. cdcntuliis and 

 P. muticus are practically identical. I shall describe the mouth parts 

 of P. cdentuhis. 



The mandibles are rather powerful chitinized structures. Each ends 

 in a sharp hollow projection (Fig. 20). On the inner face just below 

 the projection is a prominent tooth-like elevation. Each mandible is 

 pierced by a hollow, cylindrical tube opening into the mouth at the 

 base and at its tip in the hollow projection. The tube gradually 

 widens towards its proximal end. In Figs. 20, 21, the hollow tubes 

 are shown in dotted lines. Powerful muscles are attached to the 

 inner face of each mandible. Each mandible bears five long setae on 

 its outer edge. 



The maxillae are rather complicated structures (Fig. 23). Each 

 consists of a basal segment and a large distal one bearing a two- 

 jointed palpus and a chitinous projection on its inner face. This 

 projection bears many small setae. Setae are found scattered over the 

 maxillae. The labium consists of a submentum and a mentum bear- 

 ing a single jointed palpus (Fig. 23). 



The mouth parts of H. riificollis are well figured and described by 

 Schiodte in his De Metamorphosi Eleutheratorum, Vol. I, p. 72, Plate 

 VIII, Figs. 5, 6, and 7. 



The Larval Legs. — The larval legs with the exception of the first 

 pair, are practically identical in the two genera studied. The first 

 pair are fitted for grasping and are held forward and closely applied 

 to the lower surface of the head. The other two pairs are long and 

 slender, well fitted for walking over filamentous algae. Each leg con- 

 sists of five segments and a single claw (Fig. 27). The claw bears a 

 short basal spine. The prothoracic legs are remarkably adapted for 

 grasping. In H. ruficollis the penultimate segment is prolonged on its 

 inner side and bears two large lateral and apical spines (Fig. 24). 

 Against this prolongation fits the last segment while the claw falls 

 between the last pair of spines. In P. cdentuhis and P. muticus the 

 prolongation bears, besides the spines, a series of sharp serrations 



