436 NEW YORK STATE MUSEUM 
very close together so that they appear as one. The first three 
segments in specimens which are ready to transform are en- 
larged and represent the thorax; the intermediate segments are 
subequal in length and apparently without trace of setae. On 
the ventral surface of the 11th are two pairs of long blood gills 
[fig.7], on the caudal end of the dorsal aspect of the last segment 
are two tufts of five or six long hairs; ventrad of whichisa bunch 
of four very short processes. The anal feet are about as long as 
the 11th segment, each one with a crown of 12 to 15 bifid claws, 
resembling the one shown on plate 50, figure 9, but sharper, 
straighter and more slender, and the inner one comparatively 
shorter, the angle between the two teeth being about 60°. 
The pupa [fig.12] is elongate, its abdomen eight segmented, 
not counting the anal appendage. The usual respiratory fila- 
ments of Chironomus, consist of a pair of much branched tufts. 
On the lateral margins of each of the segments are a few deli- 
cate, transparent filaments [fig.10]; of these there are five pairs 
on the eighth segment, besides a pair of chitinized toothed 
claws. On the margin of the anal segment is a close row of 
hairs, the basal portions of which are stout, but extremely fine 
at the extremity, where they become matted, forming a paddle 
[ fig.10, 12]. , 
Of course no adults were found in the material, but from 
some nearly mature pupae the flies were withdrawn, and these 
possess the following characters. Length, 7 to 8mm. Dorsum 
of thorax brown, with the usual three dark dorsal stripes; 
pectus darker brown; dorsum of abdomen paler brown, the 
incisures whitish; the ventral surface of each segment with a 
large, rectangular brown spot, the rest whitish; legs yellowish 
brown; the tips of all joints blackish. Metatarsus longer than 
the preceding joint; all tarsal claws simple. Male genitalia 
complex, consisting of two pairs of blunt lobes, the outer pair 
the longer; a pair of two jointed claws; and on the dorsal aspect 
is a single large, heavily chitinized, downward curved hook. 
Figure 11 shows a side view, the dorsal surface being turned 
uppermost. The colors given in the above description are doubt- 
less intensified in the living fly. -It is hoped that by means of 
this description the fly may later be recognized. 
THALASSOMYIA Schiner 
Plate 50, fig.1-15 
Verh. Zool. Bot. Ver. 6:216, 1856 
This is the first record of the genus from North America. As 
far as I am aware, but two species have been described, T. 
frauenfeldi Schiner and T.congregata Tomasovary, 
