310 Forty- SIXTH Report on the State Museum 



have been one of these, it would account for the absence of any early 

 notice of its peculiar habits in hibernation that would naturally have 

 attracted observation to it. 



What the Fly Is. 

 The fly has been sent to me on several occasions during late years, 

 with inquiry if it was the common house-fly, and telling of its abund- 

 ance or strange conduct that di'ew attention to it. 



While belonging to the same family with Musca domestica^ viz., the 



Muscidce, and to the ordinary observer 

 bearing a general resemblance to it ia size 

 and appearance, a com23arison of the two 

 would show marked diiferences between 

 them. P. rudls may be recognized by its 

 sluggish movements when on or about the 

 "^ " windows, as if partiall}^ stupefied; a some-. 



Fig. 7. — The cluster fly, PoLLENiA i^i • xi"i^7 ^• 



RUDis. corigiaai) wiiat larger Size than Jz. doniestica; its 



black thorax (in fresh examples) covered with rather closely appressed 

 tawny-colored hairs, sometimes inclining to a green shade; its grayish 

 abdomen marked above with two black quadrate spots on each segment, 

 and a black edging to the segment; and its black legs. See fig. 7. 



So little was known of the insects of our country fifty years ago 

 that it is not surprising that among the manuscript material left by Dr. 

 Harris, there should be found descriptions of the two above-named 

 species, under the names of Musca liarpyia and Musca familiaris, — 

 the former since recosrnized as the common house-flv, and the latter the 

 cluster fl}^ 



When with progress in entomology it was found necessary to sub- 

 divide the old genera of Linnaeus, Fabricius, etc., the genus of PoUenia 

 (suggested by the pollen of flowers) was founded b}^ R. Desvoidy in 

 1830 for those Muscids having, among other features, the thorax cov- 

 ered with a down-like clothing, classing them as "Miiscida^ tomeJitosmy 

 P. iiidis was named as the type of the genus, which included about 

 twenty European species. Of North American species, Osten Sacken 

 (1878) has named but one other PoUenia, P. vesj^illo, occurring in 



Nova Scotia. 



Its Common Nam.e. 



The popular nanie of the " cluster fly " has been given to this insect 

 in consideration of its habit of leaving the flowers, fruits, branches or 

 trees, walls, etc., upon which it is often to be seen during the summer 

 months, and entering dwelling-houses in the autumn, for hibernation, 

 where it gathers at times in large clusters on the walls and ceilings, 

 and especially in the corners that they form. 



