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POLLEN-EATING FLIES. 
XXYII. Pollen-Eating Plies. By A. W. Bennett, M.A , B. Sc., 
P.L.S. 
[Read Dec. 3, 1873.] 
The reading oT the paper entitled, " Do Plies eat Pollen? " before 
the Scientific Committee of the Eoyal Horticultural Society on Dec. 
7, 1872,^' called forth the suggestion from the Eev. M. J. Berkeley 
that it would be desirable to ascertain whether the pollen-grains 
are actually digested by the insect, or whether they pass through 
its intestinal organs unchanged. It was then too late to prosecute 
the enquiry during that season ; but in the course of the present 
autumn I have made some further experiments. My hunting- 
ground was, as before, the'* Compositae" bed in the herbaceous 
department of the Eoyal Botanic Society'*' gardens, and the species 
examined chiefly the same as before, Eristalis tenax and Sijrphm 
clypeata, both belonging to the family of Syrphidse. As before, I 
found in almost every case the stomach perfectly loaded with 
pollen-grains, all presenting the form characteristic of plants 
belonging to the order Compositae, though varying considerably in 
size, indicating probably that they belonged to several different 
species of Aster. The bodies of the common house-fly and of other 
Diptera belonging to the family Muscidae, which were also captured 
browsing on the Asters, were in most cases entirely destitute of 
pollen, in other cases a few solitary grains were found, probably 
accidentally sucked up with their liquid food through the proboscis. 
A more careful examination under the microscope of the contents 
of the stomachs of the Syrphidse showed the pollen-grains in eveiy 
possible state of disintegration and digestion. It is clear that after 
remaining for a short time in the stomach, the coating of the pollen- 
grain (extine and in tine) gives way, and the liquid contents of the 
grain are digested by the assimilating organs of the insect. Large 
accumulations of the coats or skins of the pollen-grains were found 
evidently on the point of being expelled from the intestines as 
indigestible exuviae, having then assumed a very deep orange 
colour. There can be no doubt, therefore, that to a large class of 
Diptera, pollen forms a not inconsiderable or unimportant article of 
food. 
* See Journal of the R.H.S., n.s., vol. iv., p. 30. 
