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. Dall, 

 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 Dall 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- 



