AQUATIC INSECTS IN NEW YORK STATE 299 
of three segments, an eighth, ninth, and a minute tenth. When 
the dorsal aspect of the segments in front of this region is 
studied, they are found to be divided transversely into two sub- 
segments, each subsegment bearing a transverse band of setae. 
If we compare this with the region behind the seventh segment, 
we find that there are four indistinctly marked transverse divi- 
sions, each bearing a band of setae, which would seem to indi- 
cate that we have to do with two segments. But, when the 
ventral aspect is studied, we find that the transverse divisions 
separating the segments into subsegments are wanting, and 
that each transverse line marks the suture between two seg- 
ments, and, when the portion beyond the seventh segment is 
examined, there are found two transverse divisions [pl.27, 
figs. 17 and 19], which proves conclusively that this portion is 
made up of three segments, making 10 abdominal segments in 
all. The first transverse division on the dorsal aspect caudad 
of the seventh segment is the suture dividing the eighth seg- 
ment into subsegments; the ninth and 10th segments are not 
divided into subsegments. These conclusions are apparently 
refuted by plate 28, figure 17, where only a single ventral divi- 
sion is shown beyond the suture of the seventh segment, but 
a few sections on either side of the one from which this figure 
was made show two well marked ventral divisions.! 
Each segment bears a number of minute hair-like setae. The 
arrangement of these setae into definite areas and the interre- 
lation of the areas seem to furnish the best characters for sep- 
arating the larvae of the various species. It has been found 
necessary for the sake of exactness and brevity to apply names 
to these areas [pl.30, fig.1] which are as follows: 
_ The tergal setae are the double row of transverse setae on 
the dorsum of each segment, the anterior row being known as 
the anterior tergal setae [fig.lat] and the posterior row as the 
posterior tergal setae [fig.1pt]. 
, The supraspiracular setae are the patches of setae between 
the spiracles and the tergal setae [fig.1ss]. 
The infraspiracular setae are the small patches of setae imme- 
diately beneath the spiracles [fig.lis]. 
The pedal setae are the patches of setae surrounding the 
thoracic legs and on the protuberances where the prolegs would 
be situated if they were present [fig.1ps]. 
1“ The long filiform lateral appendages’”’ referred to by Mr Sanderson 
as figured by Kolliker, A. Observationes de prima insectorum genesi 
adjecta articulatorum evolutionis cum  vyertebratorum comparatione. 
Observationes de prima insectorum genesi. Ann. des Sci. Nat. (2) 1848. 
20:267-99, pl.12, fig.6, are the deciduous setae represented on pl.27, fig.138; 
and I can not see how they can have any bearing on the question of the 
homology of the segments, 
