AQUATIC INSECTS IX NEW YORK STATE 431 



fingerlike lobes, each with a marginal fringe composed of a 

 single row of stout setae; and lying between these is a third, 

 cyliudric, nearly black in color, provided apically with three 

 pairs of long black setae, and a short, pale yellow terminal joint 

 [flg.T]. The middle lobe does not extend quite so far caudad as 

 do the lateral lobes, differing in this respect from the described 

 (European) species. It is a little more than, twice as long as 

 wide. Of the four small respiratory gills figured by Meiuert in 

 De euccpJuile Mi/ggelarver nothing is to be seen in the specimen 

 from which the drawing was made, though they are present 

 in specimens discovered later. Caudad of the spiracles and 

 lying on the dorsal surface is a triangular chitinized plate, 

 the rounded vertex pointing cephalad, the basal angles each 

 provided with a single short seta [fig.T/)]. On the ventral sur- 

 face, at the base of each of the long lateral lobes, is a short, 

 semicircular lobe with a. marginal row of short, black spines 

 [fig.oo]. On each side of the middle line and, caudad of the small 

 lobes is a black ridge or keel with two black setae, the longer 

 one projecting caudad, the shorter one projecting laterad; and 

 extending transversely between the bases of these setae is a mat- 

 ted fringe of fine, pale yellow caudad projecting hairs. 



Pupa. The pupa [fig. 4] is pale fuscous. The single observed 

 fspecimen assumed a nearly circular position, its caudal end 

 nearly touching its head, and remaining motionless on the side 

 of the glass above the water film. Normally a Dixa pupa rests 

 on its side, and according to Meinert it may thrive either in or 

 out of water. The length of pupal life is about three days. No 

 setae were observed on any portion of its body. The breathing 

 trumpets are short, with widely flaring conical mouths. There 

 are eight abdominal segments besides the anal one. The anal 

 segment has two long, pointed lobes with very finely serrate 

 margin and a few short, terminal hairs. 



The larva on which this description is based, was found in 

 Ithaca N. Y. in a slow flowing stream Ap. 11, 1902; it pupated 

 Ap. 18, and emerged three days later. A number of specimens 

 were found in October. 



KEY TO SPECIES OP DIXA 



In order to facilitate identification, the following key is 

 offered, which must however be used with caution, as it is in part 

 compiled from descriptions. 



1 Species having botla tlie proboscis and the scutellum yellow (2) 



Having either proboscis or scutellum black (4) 



