216 DISEASES OF INSECTS. 



of the same description ; and I even saw one upon its 

 wing. Upon a former occasion I mentioned a parallel 

 circumstance with respect to a species of Xylocopa a . 



ii. The animal parasites that infest insects are either 

 themselves insects , or 'worms. 



1 . Their insect infesters, as far as we know at present, 

 are confined to the Orclers Strepsiptera, Hymenoptera, 

 Diptera, and Aptera : they attack them sometimes in their 

 egg state, most frequently when they are larvae, occasion- 

 ally when pupae, and very rarely in their perfect state. 

 Upon many of these I have formerly enlarged b , and 

 I shall now add such further circumstances as I then 

 omitted. The Strepsiptera Order, as at present known, 

 consists only of two genera, Stylops and Xenos ; the first 

 being appropriated to the imago of Andrena, a kind of 

 bee, and the latter to that of the wasps. Their eggs ap- 

 pear to be deposited in the abdomen of these insects in 

 which they feed, till having attained their full growth 

 they perforate the membrane that connects its segments ; 

 andat the proper time their pupa-case bursts, they emerge, 

 and take their flight. Sometimes four or five infest a 

 single bee. Whether the latter dies upon their quitting 

 it I have not been able to ascertain, but from their fly- 

 ing, when the little parasite is very near leaving them, 

 with their usual activity, it should seem that this disease 

 is not mortal ; but it probably prevents their breeding : 

 I do not recollect observing the exuviae of one in a male 

 bee c . 



The great body of insect parasites, however, belong 

 to the Hymenoptera Order, and chiefly to the Linnean 

 genus Ichneumon. The insects of this order have been 



z VOL. III. p. 335. |J VOL. I. p. 267. 



c Mon. Ap. Angf, ii. 111. Linn. Trans, xi. 90. 



