22 FLIES FOUND IN HOUSES 



distinguished, very few members of the families mentioned, 

 difficult to distinguish from M. doincstica, enter houses. 

 Consequently in collections from houses M. doniestica can be 

 identified fairly easily from other species. 



Mtisca co7'vina F. The raven fly. 



This fly closely resembles the house-fly {M. doniestica) in 

 general appearance, but the male has a yellow abdomen with a 

 very distinct black longitudinal stripe, and the female a 

 chequered abdomen. (PL II, figs. 2 and 3.) 



Length. 6 mm. ; span of wings 12 mm. 



Head. In the cT the eyes almost meet, but in the ? are separated by an area equal 



to one-third of the diameter of the head. The frontal stripe is black, the frontal 



margins of the eyes, cheeks and face white. Antennae dark. Arista feathered 



except the terminal one-fourth. 

 Thorax. In S dark grey, with poorly marked darker longitudinal stripes ; in ? lighter 



grey with the longitudinal darker stripes better marked, especially at the anterior 



part. There are long black bristles on the sides and on the scutellum. 

 Wings. Clear, but slightly yellow near the base. Squama whitish and more opaque. 



Halteres hidden under squama. 

 Le^s. Black. 

 Abdopien. In i bright yellow with a black median longitudinal band, of varying 



width ; in ? dark and grey markings. 



This fly frequently hibernates in country houses. 



The larvae live in excreta, especially horse manure. M. 

 corvina only lays 24 eggs, which are larger than those of the 

 house-fly, and the larvae are said to develop very rapidly, so that 

 the fly comes to maturity sooner than M. doniestica, thus 

 counterbalancing the low power of fecundity. 



Calliphora erythrocephala Mg. The blow-fly or blue-bottle. 



This is a large stoutly built fly, of metallic dark blue colour, 

 which produces a loud buzzing sound during flight. (PI. Ill, 

 fig. I.) 



Length. 12 mm. ; span of wings 25 mm. 



Head. The eyes, which are red, are close together in the i being separated by an 

 area equal to one-tenth of the diameter of the head. In the ? they are sepaiated 

 by an area equal to one-third of the diameter of the head. The frontal stripe is 

 black, the frontal margins of the eyes and upper ]5arts of the cheeks whitish. The 



