DISEASES OF INSECTS. 209 
Upon many of these I have formerly enlarged*, 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 dee, aud the latter to that of the wasps. Their eggs 
appear 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 ; 
and at 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 exuviz of one in a male 
bee?. 
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 
denominated Princzpes, because of the wonderful instincts 
of ants, wasps, bees, and other gregarious tribes that be- 
long to it; and they merit a name of honour not less for 
the benefits that they confer upon mankind, by keeping 
within their proper limits the various insect-destroyers 
of the produce of the globe. It deserves notice that 
when these latter increase to a degree to occasion alarm, 
their parasites are observed to Increase in a much greater, 
so as to prevent the great majority of them from breed- 
2 Vor. I. p. 264—. 
> Mon, Ap. Angi. ii. 11. Linn. Trans. xi. 90—. 
VOL. IV. P 
