578 NEW YORK STATE MUSEUM 



from the District of Columbia, from Cambridge Mass. and from Nor- 

 way Me. It was quite common at Saranac Inn in Little Clear creek, in 

 places where the creek flows through beds of bur reed, Sparganium, 

 intermixed below the surface of the water with river weed, Potamoge- 

 t o n, and algae. 



The flies sit on the erect burred leaves, with wings laid flat on their 

 backs, their long hind legs folded together, the tip of the abdomen slop- 

 ing down and nearly touching the leaf and the head lifted up high above 

 it, in quite a froglike attitude. They fly but little — that little rather 

 poorly — sweeping betimes, from one resting place to another near by. 

 They rest on the leaves head downward more often than otherwise; I 

 have frequently seen them sitting thus, close to the surface of the water, 

 and apparently feeding on the stuff which collects about the bases of the 

 leaves just above the water line. 



Nothing has been written concerning the life histories of any of our 

 few American species. When, in the course of a quantitative study of a 

 little section of the creek border, I first noticed the singular pupae, after 

 handling them for half an hour and throwing a number aside, having mis- 

 taken them for floating seeds (see pi. 14, fig. 4 and 6), and when I found 

 also the larvae, likewise floating, exhibiting a muscid anterior and a tipu- 

 loid posterior end, and hook-bearing, dorsal prolegs for crawling beneath 

 the surface film, I was sure I had found something of which I had read 

 no account, and something it would be worth while to raise, if possible. So 

 I stocked several of my floating cages (fig. i) with larvae and pupae. 



When imagos had emerged and had been determined, I found in 

 Brauer's list of the described transformations of Diptera' that immature 

 stages were known for two European species of the genus: S. sphegius 

 and S. s p i n ip e s ; but I have not been able to find the paper in which 

 these are described ' . 



Larva. (PI. 14, fig. 1,2.) Length full grown 11-12 mm; greatest 

 diameter 2 mm. 



Color yellowish or greenish brown of varying depth in different spec- 

 imens, with tracheae showing through the thin integument more or less 

 distinctly. 



Body cylindric, strongly tapering anteriorly from the second abdominal 

 segment, slightly tapering on the upturned posterior end behind the sev- 

 enth abdominal segment ; skin granular ; head segment minute, blackish, 

 retractile within the prothorax ; the thoracic segments strongly retractile 

 and protrusible, almost telescopic; mesothoracic twice as long, and meta- 



1 Brauer, F. (Syst. studien Dipt, larv.) Denkschr. math-nat classe k. acad. wiss. Wien. 1883. 

 47 : 1-100, 5 plates. 

 - Gerke. Vehr. d. nat. unterhalt. Hamburg 1876. 3: 145, pi. 3. 



