STRUCTIJKE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 357 
of houses, especially during wet weather, from which habit it 
has no doubt derived the popular name of “ storm-fly ” ; it is 
also know as the “stable-fly.” As these names may be equally 
applicable to certain other Diptera they should be discarded. 
As I have already mentioned this species is frequently mis- 
taken by the public for M. domestica, which is supposed to 
have adopted the biting habit, although the latter is unable 
to inflict the slightest prick. IE examined side by side the 
sreat differences between the two will be seen readily (see 
Part I in ‘Quart. Journ. Micr. Sci., vol. 51, PI. 22, _fig. 4). 
S. calcitrans has an awl-like proboscis for piercing- and 
blood-sucking ; this projects horizontally forward from 
beneath the surface of the head (fig. 4). It is slightly 
larger and more robust than M. domestica; the bristles of 
the antennae bear setm on their upper sides only. The colour 
is brownish with a greenish tinge ; the dorsal side of the 
thorax has four dark longitudinal stripes, the outermost pair 
being interrupted. At the anterior end of the dorsal side of 
the thorax the medium light-coloiu-ed stripe has a golden 
appearance, which is vei-y distinct when the insect is seen 
against the light. The abdomen is broad in proportion to its 
length, and each of the large second and third segments has 
a single median and two lateral brown spots; there is also 
a median spot on the fourth segment. 
The life-history of S. calcitrans has been studied by 
Newstead (1906), and I have been able to confirm his observ'a- 
tions during 1907 and 1908. From fifty to seventy eggs, 
measuring 1 mm. in length, ai-e laid by the female. The eggs 
are laid on warm, decaying vegetable refuse, especially in 
heaps of fermenting grass cut from lawns ; I have frequently 
confirmed this observation of Newstead’s. The eggs are also 
deposited on various exci-emental substances upon which the 
larvc© feed. Osborne (1896) reared them in horse-manm-e ; 
Howard (1900) states that they live in fresh horse-manure, 
and records their occurrence in outdoor privies in some 
localities; Newstead reai-ed them in moist sheep’s dung; they 
can also be reared in cow-dung. 
