of the Oil Beetle, Meloé, and of the Strepsiptera. 335 
On the 19th of May 1845, I received a female specimen of Andrena Trim- 
merana from Mr. W. Wing, which he had captured at Hampstead on the pre- 
ceding day, with a Stylops projecting from beneath the fourth abdominal 
segment. This specimen I preserved in spirit for dissection. On examining 
it I found the body of the Stylops, which was a female, greatly enlarged, and 
occupying at least one-fifth of that of the interior of the bee. It extended 
backwards from the fourth segment of the abdomen to the base, on the dorsal 
surface, forcing downwards and compressing the whole of the viscera, which 
were more or lessatrophied. Thealimentary canal of the bee was almost empty, 
and thrust out of its usual position ; the respiratory organs were small and im- 
perfectly developed, and retained more the tracheal condition of the bee-larva 
than that of the adult insect, the vesicles being few and imperfect. The 
secretory vessels and poison-bag of the sting also were of diminutive size, and 
even the ganglia of the abdominal portion of the nervous cord seemed to have 
been atrophied, and were smaller than usual. But the most marked effect of 
the parasite on its victim had been produced on her organs of reproduction. 
The oviducts were of ordinary length and size, but the ovaries were entirely 
undeveloped, and were scarcely larger than they are at the period when the 
bee-larva passes to the state of nymph. They contained only the germs of 
a few very imperfect ova. 
These effects on the development of the internal organization of the bee, 
and of all insects which undergo a complete metamorphosis, are the usual 
results of the exhaustion of their vital energies by the presence of internal 
parasites. I have constantly observed like effects produced on the organiza- 
tion of the Sphinx Ligustri by its internal parasite, the larva of Ichneumon 
Atropos ; and these effects are equally injurious to the male as to the female 
victim. They seem to be produced mainly by the abstraction by the parasite, 
—which subsists on the adipose tissue, and not on the viscera of its victiin,— 
of a portion of that supply of nourishment which is accumulated in its body 
during the feeding or larva state, to furnish materials for the growth and de- 
velopment of the whole organism. 
In a male pupa of Sphinx Ligustri, which I preserve, the facts now stated 
pus well shown. ‘he full-grown larva of the Ichneumon, imbedded in the fatty 
tissue on the dorsal surface of the body, has compressed the alimentary canal, 
