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 ob-^ervation 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 abimd- 



ance or strange conduct that drew attention to it. 



While belonging to the same family with Ihcsca domestica, viz., the 



Muscidd', and to the ordinary observer 

 bearing a general resemblance, to it io size 

 and appearance, a comparison of the two 

 would show marked difi^erences between 

 them. P. rudis may be recognized by its 

 sluggish movements when on or about the 

 windows, as if partially stupefied; a some- 



FiG. 7. —The cluster riy, PoLLBNiA i,i • ^\ nr i 



BUDis. (Original) wliat larger size than M. domestica; its 



black thorax (in fresh examples) covered Avitli 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 surj)rising 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 harpyia and Whisca famiUaris, — 

 the former since recognized as the common house-fly, and the latter the 

 cluster fly. 



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

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

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

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

 ered with a down-like clothing, classing them as ^'Miiscidm tomejitostje.'''* 

 P. rudis was named as the type of the genus, Avhich included about 

 twenty European species. Of North American species, Osten Sacken 

 (1878) has named but one other Pollenia, P. vespillo, occurring in 



Nova Scotia. 



Its Common Name. 



The popular name 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 dAvelling-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. 



