INTERNAL ANATOMY OF INSECTS. 139 
thing similar has been observed by Reaumur witli re- 
gard to the larva of Crioceris merdigera, which forms its 
cocoon with a kind of froth produced from the mouth 3 . 
iii. Varnish or Gum. The eggs of various insects, when 
they leave the oviduct, are covered with a kind of var- 
nish or gum by which they adhere to the substances 
that the young larvae are to feed upon, or are placed in 
a proper position for their hatching in an appropriate 
station. Several instances of this have been already 
mentioned 13 ; I shall therefore not enlarge further upon 
the subject. With regard to the secretion itself, little 
has been recorded except its colour, which has been be- 
fore noticed. Some Lepidoptera also as we learn from 
Reaumur and Bonnet , use a varnish in the construc- 
tion of their cocoons. 
iv. Jelly or Gluten. This secretion is particularly con- 
spicuous in the Trichoptera and some Diptera, serving 
as a bed or nidus for those eggs that are committed to 
the water, — upon which I have nothing to add to what 
has been before said d . Under this head also may be 
noticed the fluid, secreted in peculiar vesicles, that lu- 
bricates the oviduct and the passages of the sexual or- 
gans e . 
v. Oils. Oily substances are sometimes produced by 
insects. The common oil-beetle (Meloe Proscarabceus) 
when touched sends forth a drop of this kind of fluid, 
of an orange colour, from each joint of its legs f : some- 
thing similar I have observed in Coccinella bipunctata : 
a Reaum. iii. 230. >> Vol. III. p. 79— 
c Reaum. iii. 215. Bonnet ix. 182. d Vol. III. p. 68—. 
• Marcel de Serres Mem. <lu Mus. 1819. 133, 141. 
f Dc Geer, v. C. 
