sf fae 
In Osten Sacken’s Catalogue of the Diptera, five species are reported 
as occurring in this country north of Mexico, as follows: S. decorum 
Walk., S. invenustum Walk., S. piscicidium Riley, S. venustum Say and 
S. vittatum Zett. 
Since the date of that publication descriptions of five supposed new 
species have been published, as follows: 
Simulium pictipes Hagen, Proc. Boston Soc. Nat. Hist., Vol. XX, p. 305; 1881. 
pecuarum Riley, Annual Rept. U.S. Dept. Agric. for 1886, p.512; 1887. 
meridionale Riley, l. ¢., p.5138. 
occidentale Townsend, Psyche for July, 1891, p. 107. 
argus Williston, N. Amer, Fauna, p. 253; May, 1893. 
The type specimens of the three species described by Professor Riley 
are now the property of the National Museum. ‘Two of these species 
are synonyms, viz: piscicidium Riley equals venustum Say, and pecu- 
arum Riley is the same as invenustum Walk. 8. occidentale Towns. is 
the early part of May or at the beginning of the first continuous warm weather in 
spring. The eggs are deposited on rocks over which the water is flowing. The flies 
hover in little swarms a foot or two above the rock, flying rapidly back and forth 
and occasionally darting down and depositing their eggs beneath the water on the 
flat surface of the rock. The patch of eggs becomes at least a foot or more in 
diameter, and is distinctly observable at some distance on account of the light yellow 
color. When the water is very shailow and its velocity slight, the flies sometimes 
crawl over the surface of the rock and deposit eggs without flying. Only a small 
proportion of the eggs produce larve. The larvie hatch about eight days after the 
eggs are laid, and in this stage the insect may be found at any season of the year, 
through the hottest weather in summer as well as the coldest weather in winter. It 
is in this stage that it hibernates. Rapid motion of the water is essential to the life 
of the larve, which die within three or four hours if placed in quiet water. Fas- 
tened to the rock by the anal end of the body, they assume an erect position and 
move the head around occasionally with a cireling motion. 
They may release themselves, and as they grow larger they sometimes allow them- 
selves to be washed into deeper water, holding by a thread which they spin as they 
go. The thread is spun from the mouth, but is attached along the side of the body 
to the different segments. Sometimes a large cluster of larvie will cling to the same 
thread, which they can ascend in much the same manner as do spiders. In the winter 
the larval fans are usually kept vlosed, and not much food is taken. During the 
summer the length of the larval life is about four weeks, varying somewhat with 
the temperature and the velocity of the water. At full growth the larva spins its 
cocoon, firmly attaching it to the rock and also to adjacent cocoons. The length of 
the pupal stage is about three weeks. Over-wintering larvie transform to pupx 
about the 12th of April, the first flies appearing on the 2d of May, The newly bred 
fly, surrounded by a bubble of air, quickly rises to the surface of the water and flies 
away instantly. The first brood having appeared in early May, successive genera- 
- tions are produced from this time on during the summer and part of the autumn, 
All of the flies captured from the first brood were females, but toward autumn the 
males began to appear in greater numbers, and toward the last of August nearly all 
the specimens taken were males. [On September 2, 1888, the present writer cap- 
tured fifty specimens of this tly at Ithaca, and all were males with the exception of 
one.] Adults were observed on the wing as late as the 10th of October. Many points 
not here touched upon were brought out in the thesis, which should be published in 
full.—L. O. H. 
