DISEASES OF INSECTS. 217 
denominated Principes, 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- 
ing \ Though these benefactors of the human race con- 
stitute numerous genera, at present not well ascertained, 
I shall speak of most of them under the common name 
of Ichneumon. 
The appearance of these little four-winged flies puzzled 
much the earlier naturalists : — that a caterpillar usually 
turning to a moth or butterjly should give birth to my- 
riads of jlies, was one of those deep mysteries of nature 
which they knew not how to fathom b : even the pene- 
trating genius of our great Ray, though he ultimately 
ascertained the real fact c , was at one time here quite at 
fault ; for he seems at first to have thought, when from 
any defect or weakness nature could not bring a cater- 
pillar to a butterfly, in order that her aim might not be 
entirely defeated, that she stopped short, and formed 
them into more imperfect animals d . 
Before I detail more particularly the proceedings of 
Ichneumons, I shall make a few general remarks upon 
them. The structure of the instrument by which they 
are enabled to deposit their eggs in their appropriate 
station has been before sufficiently described e ; it is long 
a Rcaum. ii. 439. b Ibid. 415. Mouffet 57. 
c Hist. Ins. Pracf. xv. d Cat. Cant. 137. 
e Sec above, p. 1G2 — . 
