408 NEW YORK STATE MUSEUM 



Plate 15 shows the forms which I found together in this little rapids by 

 the railroad. Simulium is vastly more numerous, in individuals than all 

 the other species put together and also more restricted in its habitat. 

 The next in numerical importance would probably be the pygmy May 

 fly, Baetis pygmaea Hagen, though a larger Mayfly, Hepta- 

 genia pulchella Walsh, and a caddis fly, Hydropsyche sp.? 

 (see p. 566 ) seemed almost as numerous. These three species are 

 probably predatory, feeding on the members of the Simulium colony. 

 The other members of this Kttle society are much fewer. They are i) a 

 hitherto unknown fly of the family Empididae, Roederiodes juncta 

 Coq., (described post at p. 536 ) whose larvae crawl about among the 

 Simulium pupa cases, and pupate within empty cases, and 2) the stone 

 fly, Leuctra ten ell a. 



It must be another, earlier species of black fly which makes all the 

 trouble in the Adirondacks with its bites ; for this one is quite peaceably 

 disposed. Guides have a saying, that, when the black flies put on their 

 white stockings in June, the trouble is about over. This species has the 

 " white stockings." 



I was interested in watching the females of this species ovipositing, and 

 saw the operation very frequently. The place selected is always at the 

 edge of a little waterfall, on a surface that is intermittently washed by the 

 swaying current, and so kept wet {seepL 15). Here the females flock, 

 and pile up great white masses of eggs, which with a little age turn 

 yellowish. Waves dash over them while ovipositing, and often sweep 

 them away, but they at once return to their task. 



I do not know what Simulium larvae feed on ; but their tentacles seem 

 weU adapted for straining plankton from the water that dashes over them. 



The life of the hatchery pipes and troughs. The life of the 

 pipes is essentially that of the rapids.^ What is living in the pipes is 

 learned by observing what comes out of them, into the hatchery troughs 

 and into the windows. Simulium, Hydropsyche, Hepta- 

 genia and Baetis, were in the hatchery windows throughout the 

 session, often in enormous numbers. Their periods of greatest abund- 

 ance do not coincide however. The windows were fairly darkened with 

 black flies and caddis flies and the larger May flies, Heptagenia, 

 during the earlier part of the session^ while the pygmy May flies did not 

 appear in swarming numbers till the latter part of it. The only member 

 of the Simulium society as portrayed in the plate, which was not observed 



1 It appears that the moUusks which get into city water pipes and sometimes cause trouble are 

 forms that normally live in rapids. 



