of the Oil Beetle, Meloe, and of the Strepsiptera. 335 



On the 19th of May 1845, I received a female specimen oi Andrena Trim- 

 merana from Mr. W. Wing-, which he had captured at Hampstead on the pre- 

 ceding day, with a Stylopn 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 less atrophied. The alimentary 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 eflfect 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 

 Atropon ; 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 victim, — 

 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 

 are well shown. The full-grown larva of the Ichneumon, imbedded in the fatty 

 tissue on the dorsal surface of the body, has compressed the alimentary canal. 



