HABITS OF POLLENIA RUlJiS 207 



thoy came out of the grass and tiew up to the sunny side of 

 houses, which they entered. They remained in evidence until 

 some time in May and then disappeared until September. Large 

 numbers were said to occur often under buildings, between the 

 earth and the floor. An examination of these flies and a com- 

 parison with Miisca doniestica will show their distinct character. 

 Their characteristic sluggish habits have already been mentioned. 

 They are slightly larger in size and darker in colour and the 

 thorax is sparsely covered with yellowish coloured hairs. When 

 at rest the wings are folded more closely together over the back 

 than is the case of the house-fly. 



As in the case of many other common species of Diptera, we 

 have little information in regard to the breeding habits of this 

 species. Robineau-Desvoidy states that the flies of the genus 

 Pollenia deposit their eggs on decomposing animal and vegetable 

 matter ; in this regard they resemble, in general, the other members 

 of the Muscidae. Howard (1910) records the rearing of a single 

 specimen of P. rudis from cow manure in Washington D.C. in 

 December, and quotes J. S. Hine as reporting the rearing of 

 numbers of Cluster flies in the summer of 1910 from cow manure 

 in the pasture. Copeman, Hewlett and Merriman (1911) record 

 the occurrence of three specimens of P. rudis in a collection of 200 

 larvae and pupae obtained from fresh refuse on the Norwich 

 Corporation tip at Postwick. Keilin describes P. rudis as parasitic 

 on a species of earthworm Allohophora chlorotica Sav. He states 

 that it pupates in the earth, the pupal stage lasting from thirty-five 

 to forty-two days. 



MUSCINA STABULANS FaLL. 



So similar is this fly to the true house-fly in general appear- 

 ance, though slightly larger in size, that it is almost invariably 

 mistaken by the untrained observer for a large house-fly. Ac- 

 cording to my own observations it usually occurs in and near 

 houses in the early summer, about June, and generally about the 

 same time that the Lesser House-fly, Fojiinia canicularis, is the 

 predominant domestic species. Hamer (1910) found that the 

 largest number of M. stabulans were captured in August and 

 early September. In large collections which have been made in 



