AQUATIC INSECTS IN NEW YORK STATE 



283 



placed in a watch glass of water, these flaps will be seen to 



be separated, and there will be protruded between them four 



curved triangular, delicate, whitish, elongate gills, showing in 



their interior both tracheae and blood currents. These are 



■doubtless respiratory appendages of the terminal portion of the 



walls of the rectum. A similar eversible condition of this part, 



with a much less perfect development 



•of the gills themselves, has recently 



been described by Pantel in the 



Bulletin de la SocieU entomologique de 



France, 1901, page 59-61, for a Tach- 



inid larva. The eversible portion of 



the rectum Pantel calls the anal 



vesicle, and to it he very properly 



attributes a respiratory function. 



These four gills in Epiphragma 

 are comparable to the four anal 

 processes of the larva next to be 

 ■described, and shown on plate 10, 

 fig. 4, even to the constriction forming an apparent seg- 

 ment near the tip. They are comparable and homologous 

 •doubtless with the anal processes of other Tipulidae. There, 

 liowever, they are permanently on the outside of the body, 

 being no longer retractile. The end of the rectum has become 

 permanently everted in these more aquatic larvae. The larva 

 of Epiphragma is therefore specially interesting as showing 

 what has been the course of development of this part of the 

 very curious caudal armature of the typical Tipulid larvae.i 



Larva [pl.9, fig.l]. Length 19mm; greatest diameter (base of 

 thorax) 1.5mm. Cylindric, white, or faintly tinged with yellowish, 

 with translucent sides and a brown head capsule. Head large, for 

 the family, with pale antennae and labrum and stout blackish 

 mandibles and labium. On the ventral side of each of the three 

 thoracic segments is a pair of minute brownish points— vestiges 



Fig. IS Anal gills of the larva of 

 Epiphragma fasclpeunis 



lElsewhere {American Naturalist, 3G:1S5) I have pointed out, iu a descrip. 

 tion of the larva of B i b i o f r a t e r n u s , that the segmental tubercles 

 have offered the material out of which have been formed the other fleshy 

 tubercles which surround the caudal respiratory dislj 



