382 
Parasites oj Common Flies 
Both exposed larvae and those hidden under folds of skin, etc., are 
attacked. The parasite frequents such situations and often inserts its abdomen 
into clefts and seems to feel for hidden larvae with its ovipositor. 
At least from some puparia the males emerge first. For example from one 
puparium 2 $ emerged and on examining the contents of the puparium 2 $ 
nearly fully developed were found and several female nymphs. 
Occasionally only one or two of these parasites develop in a puparium, and 
these are often very large. 
This parasite frequents both animal remains and faecal material throughout 
the summer and autumn. 
Aspilota fucicornis Hal. 
Several specimens of this small braconid were reared in August, 1917, from 
puparia found in excrement in July. 
Fig. 22. Aspilota fucicornis. x 15. 
Aspilota nervosa Hal. 
A single specimen emerged in the spring of 1917 from puparia collected in 
the previous autumn. 
CONCLUSIONS. 
1. In the year 1915 flies caught in a trap baited with excrement were 
most abundant in August and September, in 1916 in July and in 1917 in May 
and June. In each year the curve indicating the number of flies caught corre¬ 
sponds with the curve for the maximum temperatures recorded by a ther¬ 
mometer exposed in the sun. 
2. Flies spend a very large proportion of their time in cleaning themselves, 
and the procedures usually follow each other in a definite order. 
3. Empusa disease occurs in several species of flies. Specimens of C. 
erythrocephala, L. caesar, H. dentipes, F. canicularis, A. radicum , S. carnaria, 
M. corvina and S. stercoraria suffering from the disease have been noticed. 
4. Certain Gamasid mites destroy both fly eggs and young larvae. 
5. Certain species of beetles destroy large numbers of fly puparia. 
