532 Observations on Habits and Parasites of Common Flies 
Careful study of this subject might reveal new and important facts, 
which might be utilised in the artificial control of flies of various species. 
The chalcids, discovered in the 1914-15 winter puparia, which 
Mr J. Waterston 1 very kindly examined, belonged to two species, one 
of them occurring very rarely. The species, most commonly found, 
Melittobia acasta Wlk., proved to be of great interest (Figs. 16, 17). It 
only occurred in puparia from the “sun tin,” both those which had 
been there throughout the winter and those which were taken from the 
“shade box” and placed there on April 29. From the facts which 
have been given there can be little doubt that this parasite attacked 
the puparia after the beginning of May. A large number of puparia 
from this source, which either appeared to be intact or which had 
16 17 
Fig. 16. Mellitobia acasta Wlk. ( x20 and nat. size). 
Fig. 17. Mellitobia acasta Wlk. $ ( x 20 and nat. size). 
minute pin-holes in them, were examined in November (Plate XXX, 
fig. 10). In most cases only one round or oval hole was present 
in a puparium, and this was usually situated in the middle two-thirds 
of the puparium though it was occasionally found at the very end; 
in a few two holes were found. The holes varied in diameter from 
0-3 to 1 mm. Such puparia contained a dry hard mass, and some 
dry dusty material crowded with Tyroglyphidae, but a few dead 
chalcids of both sexes were usually present also. Very infrequently 
living specimens were found. Dead females were scarce, but dead 
males were very common, apparently indicating that many of the 
1 Mr J. Waterston is describing the anatomy of these parasites in papers to appear 
in Parasitology. 
