PHRYGANEID^. 



619 



it. The body of the larva is curved, though not spirally, and 

 when out of the case it is cylindrical, thickest on the basal 

 ring of the abdomen, and is pale greenish, while the head, 

 thorax and legs are brownish ; it is .25 of an inch in length- 

 The head is hairy and is smaller than usual, a little narrower 

 than the thorax, with black, acute unidentate mandibles. 

 The tlioracic rings are horny above, somewhat hairy, and 

 the legs are slender and hairy. The abdomen ^s^ 

 ends rather abruptly, with two short tubercles ^^^^j^k\ 

 ending in a hook, both sides being alike, the ^^^^^ 

 body throughout as symmetrical as other larvie Fig. 613. 

 of this family, though living in a helicoid case. On each side 

 of the basal segment of the abdomen is a lunate, corneous, 

 hair}' spot, by which the larva probablj'^ retains its hold in the 

 case when the head and thorax are protruded. The case is 

 usually very regularly helix-like in form, though tlie umbilicus 

 varies in size. It is composed of fine grains of sand so 

 arranged that the outer a 



surface is smooth. It is 

 closed during the pupa 

 state by a dense, silken 

 concave, sub orbicular 

 operculum, with concen- 

 tric lines, rounded on the 

 side, and but slightly con- 

 vex on the other, with a 

 slightl}' curved slit for the 

 passage of water situated 

 on the less convex side, 

 each side of the slit be- 

 ing provided with slender 

 straight teeth which near- 

 ly touch each other, thus 

 forming an i m p e r f e c t 

 grate. Tlie larva does 

 not spin a cocoon. Fig. 

 613 represents the case of //. arenifera Lea, from Indiana. 

 Mr. J. A. McXiel has brought from Pulvon, west coast of 

 Nicaragua, similar larva', belonging to a species very closely 



Fig. C14. 



