THE CLUSTER FLY 
237 
ing vessels, especially in the cooler season of the year, 
since it apparently hibernates in the adult condition and 
seeks the shelter of cracks and crevices. It is men¬ 
tioned by Loew in 1864 as one of the flies common to 
Europe and America. Attention was first particularly 
called to it and to its house habits by Dr. W. H. Dali, 
of the Smithsonian Institution. In an article published 
in the Proceedings of the U. S. National Museum for 
1882 (Vol. V, pp. 635-636) Doctor Dali related that 
for several years he had heard of a fly which was a 
great nuisance in country houses near Geneva, N. Y. 
He secured specimens of the fly, which were turned 
over to professor Riley for identification. 
One of his relatives in Geneva wrote him that it was 
probably thirty years since the fly had first appeared 
in that neighborhood. They were at once a terror to 
good housekeepers and a constant surprise, since they 
were found in beds, in pillow slips, under table covers, 
behind pictures, in wardrobes, and in all sorts of places. 
In clean, dark bedchambers seldom used, they would 
form in large clusters about the ceilings. They seemed 
oily, and if crushed left a great grease spot on the floor. 
The correspondent stated that about the first of April 
they came out of the grass and flew up to the sunny 
side of houses, which they entered. They remained in 
evidence until some time in May, and then disappeared 
and were not seen again until September, when they 
came and remained all winter. They were stated to be 
very sluggish—to crawl rather than to fly away when 
disturbed. They were said to be often found in incred- 
