STRUCTURE, DEVELOPMENT, AND BIONOMICS OP HOUSE-PLY, 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 fi-om 
the figure. It is compressed dorso-ventrally, and has a 
double row of processes on each side. Owing to the rough 
and spinous 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 larva) 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 in the pupal stage. 
(4) Homalomyia scalar is 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 Anthomyidm has been found in houses, 
especially those in or near the country. The female has been 
illustrated already (Part I, ‘Quart. Jonrn. Micr. Sci.,’ vol. 51, 
PI. 22, fig. 2). The male is darker in colour, the dor.sal side 
