Mr. J. O. West wood upon the Strepsiptera. 169 



XXXV. Observations iipon the Strepsiptera. 

 By J. O. Westwood, F.L.S., S)-c. 



[Read Januarys, 1835.] 



The opportunity kindly afforded me by Mr. Pickering of examining 

 a recently killed stylopized bee and its parasites has enabled me to 

 add a few particulars, in addition to those given by that gentleman, 

 and which relate, first, to the preparatory states of the Stylops, and 

 second, to its structure in the imago state. 



The bee was a female oi Andrena tibialis, and had nourished three 

 of these parasites : one of these Mr. Pickering had extracted in the 

 perfect state, having scaled off the head-case ; another, apparently 

 in the state of a larva, he had extracted ; and the third, together 

 with the exuviae of the last-mentioned individual, still remained 

 within the abdomen of the bee, all having appeared between the 

 dorsal articulations. For the purpose therefore of ascertaining 

 the structure of the parasite still remaining within the bee's ab- 

 domen, and in the hope that it might possibly be in the pupa state, 

 or perhaps ready to burst forth like the one first above mentioned, 

 I carefully removed the scales from the under surface of the abdo- 

 men, when a quantity of thick white fluid first presented itself. On 

 removing this the air-vessels and viscera were observed occupying 

 the centre of the abdomen, on one side of which was an elongated 

 fleshy white mass extended to the base of the abdomen, which 

 proved to be the body of the remaining parasite, and which (from its 

 vermiform appearance and the complete want of that solid appearance 

 which the bodies of the dipterous larvae assume when they have passed 

 into the coarctate species of metamorphosis, and inclose the true pupa,) 

 I should not hesitate to regard still as the larva of the Stylops although 

 the head was protruded. On the other side the exuviae of the first 

 individual were observed. 



Upon comparing the volume of the internal air-vessels and viscera 

 when extracted with those of a perfect female bee discovered at the 

 same time, it was at once evident that they were very considerably 

 reduced in size, and although the ovaries were perfectly distinct in 

 the latter insect, I M^as unable to perceive them in the former ; indeed, 

 as they are of considerable size, and are not conducive to the life of 

 the bee, I should consider that Mr. Kirby's supposition that their 

 presence renders the insects attacked abortive is well founded. 



