67 
In Osten Sacken'a Catalo«j:ne of tlie Diptciji, fiv(^ species sire reported 
as occuriiii«4 in this eonntry north of Mexico, jis follows: *S'. dccoriini 
Walk., iS. invenustum W'alU., !S. piscicidium Kiley, IS. rcuKstunt Say and 
S. vittatum Zett. 
Since the date of that publication descriptions of hve sn|)posed new 
species have been published, as follows: 
JShnuliuni piclipcn Hjiiioii, Proc. Hostoii Soc. Nat. Hist., V«)l. XX, ]). 305; 1S81. 
pcruantm Riloy, Annual Kopt. U. S. Dept. Aj^iic. lor 188(), p. 512; 1887. 
vieridionale Kiley, I. c, p. 513. 
occidentdlc Towuseud, Psyche for July, 1891, p. 107. 
aryus Williston, N. Amer. Fauna, p. 253; May, 1893. 
The type specimens of the three species described by Professor Kiley 
are now the property of the National Museum. Two of these si)ecies 
are synonyms, viz: piscicidium Eiley equals venustum Say, and i)ecu- 
artim Eiley is the same as invenustum Walk. S. occidentale Towns, is 
the early part of May or at tlie beginning of the first continuous warm weather iu 
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 shallow 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 larvie. The larvie hatcb a])Out 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 w^eather 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 larvae, 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 circling motion. 
They may release themselves, and as they grow larger they sometimes allow them- 
selves to be washed into deeper water, liolding 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 difi'erent segments. Sometimes a large cluster of larv;c Avill 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 *jlosed, and not much food is taken. During the 
summer the length of the larval life is about four w eeks, 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 larvje transform to pupje 
about the 12th of April, the first flies ai)pearing 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 fly 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. 
