208 THE CLUSTER FLY AND MUSGI^^A STABULANS 



North America and England of the flies occurring in houses, a 

 number of specimens of this species are usually found (see p. 66). 

 Cleland (1912) records it in New South Wales as occurring in 

 houses on the window panes or on the table at meal time ; in the 

 neighbourhood of houses he states that it is found feeding in 

 house refuse and round the garbage can. 



It is larger than M. domestica and more robust in appearance. 

 It varies from 7 to nearly 10 mm. in length. Apart from its 

 greater size it may be distinguished from M. domestica by the 

 fact that the median or fourth longitudinal vein (cf fig. 7, M. 1 + 2) 

 of the wing is only slightly curved ventrally instead of being 

 bent upwards through a pronounced angle as in M. domestica. 



Its general appearance is grey. The head is whitish-grey 

 with a " shoi " appearance. The frontal region of the male is 

 velvety black and naiTow ; that of the female is blackish -brown, 

 and is about a third of the width of the head. The bristle of the 

 antenna bears setae on the upper and lower sides. The dorsal 

 side of the thorax is grey and has four longitudinal black lines ; 

 the scutellum is gTey. The abdomen, as also the thorax, is really 

 black covered with grey ; in places it is tinged with brown, which 

 gives the abdomen a blotched appearance. The legs are rather 

 slender, and are reddish-gold or dirty orange and black in colour. 



The eggs are laid and the larvae feed upon various kinds of 

 decaying or decomposing vegetable and animal substances. They 

 have been reared from fungi, decaying fruit, such as apples and pears, 

 cucumbers and miscellaneous vegetables. They sometimes attack 

 growing vegetables, and I have reared them in considerable numbers 

 with root maggots from radishes. In the latter case the eggs or 

 young larvae may be introduced with the manure, but I have 

 found them also attacking gi-owing plants where no manure had 

 been used. Aldrich has reared it in Idaho from rotten radishes. 

 They breed in excrement, such as cow dung and human excrement 

 from which Howard (1900) reared specimens. Cleland (1912) 

 describes this species as occurring on human faeces and house 

 refuse in Australia. In Europe they have been found feeding on 

 caterpillars and larval bees and in Canada Fletcher (1900) records 

 the species as parasitic on the noctuid caterpillar Peridromia 

 saucia Hbn. in British Columbia. In the United States they 



