(114) 



STRUCTURE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 355 



mitted light. In the female the abdomen is short in propor- 

 tion to its length, and is of a greenish or brownish-grey colour 



H. canicularis appears in houses before M. domestica, 

 and can be found generally in May and June. In the latter 

 month its numbers are swamped, as it were, by M. domes- 

 tica, and it appears to seek the other rooms of a house than 

 the kitchen, although I have found it frequently in consider- 

 able numbers in kitchens. The average length is 5*7 mm. 



The larva of H. canicularis (PI. 22, fig. 1) is very 

 distinct from that of M. domestica, as will be seen from 

 the figure. It is compressed dorso-ventrally, and has a 

 double row of processes on each side. Owing to the rough 

 and spmous nature of these processes dirt adheres to the 

 larva and gives it a dirty -brown appearance. The full-grown 

 larva measures 5-6 mm. in length. The breeding habits of 

 H. canicularis are very similar to those of M. domestica. 

 The larvas feed on waste vegetable substances and also on 

 various excremental products, but particularly, I have found, 

 on human excrement, for which they show a great partiality. 

 I have frequently found excrement in privy middens to be a 

 moving mass of the larvae of H. canicularis. The larval 

 period is from three to four weeks, and the insect spends 

 fourteen to twenty-one days iu the pupal stage. 



(4) Homalornyia scalaris F. 



Newstead (1907) has found this species occurring as a 

 house-fly. It is slightly larger than, though similar in many 

 respects to, H. canicularis. The larva is very similar in 

 appearance. Newstead found the larva? in ash-pit refuse, 

 and bred the flies from human faeces. The larvae have been 

 found frequently to be the cause of intestinal myiasis. 



(5) Anthomyia radicum Meigen. 



This member of the Anthomyidae has been found in houses, 

 especially those in or near the country. The female has been 

 illustrated already (Part I, ' Quart. Journ. Micr. Sci./ vol. 51, 

 PL 22, fig. 2). The male is darker in colour, the dorsal side 



