STEUOTUEE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 363 
to this with interesting results. He submitted M. domes- 
tic a for five hours to a temperature of - 1'5° C., and they 
continued to move. Exposed for eight hours to a temperature 
of first — 3° C. and then — 2° C. they moved their legs. On 
being submitted for twelve hours to a temperature first of 
— 3'7° C. and then — 6‘3° C., they appeared to be dead, but 
on being warmed they recovered. When exposed for three 
hours to a temperature of — 10° C. which was then raised 
to — 6° C., they died. These experiments show that M. 
domestica is able to withstand a comparatively low degree 
of temperature. 
Light. — The female of M. domestica deposits the eggs 
in dark crevices of the substance chosen for the larval nidus 
and as far away from the light as possible. Bedard (1858) 
showed that the eggs develop more quickly under blue and 
violet glass than under red, yellow, green, or white. The 
larva) are negatively heliotropic, as Loeb (1890) has also 
proved in the larva) of the blow-fly. As I have pi'cviously 
shown, the distinction between light and darkness is probably 
appreciated by the larvae by means of the sensory tubercles 
of the oral lobes. 
2. Hibernation. 
'I’his (piestion is intimately connected with the preceding 
physiological facts. The disappearance of the flies towards 
the end of October and in November is a well-known fact, 
and an endeavour to discover the reason for this has been 
made in the present investigation. 
I have found that the majority of flies observed were killed 
off by the fungus Enipusa muscae Cohn which is described 
in the ])resent paper. Of the remainder some hibeinate and 
some die naturally. This natural death may be compared, 
I think, to the like phenomenon that occurs in the case of 
the hive-bee Apis mellifica, where many of the workers 
die at the end of the season by I’eason of the fact that they 
are simply worn out, their function having been fulfilled. 
The flies which die naturally have probably lived for many 
