298 MEANS OF DEFENCE OF INSECTS. 
ceal them from their enemies, make them more difficult 
to be attacked, or render them less palatable. Thus, the 
white froth often observable upon rose-bushes, and other 
shrubs and plants, called by the vulgar frog-spittle,— 
but which, if examined, will be found to envelop the lar- 
va of a small hemipterous insect (Cicada spumaria, L.), 
from whose anus it exudes, although it is sometimes dis- 
covered even in this concealment by the indefatigable 
wasps, and becomes their prey,—serves to protect the 
insect, which soon dies when exposed, not only from the 
heat of the sun and from violent rains, but also to hide 
it from the birds and its other foes.—The cottony se- 
cretion that transpires through the skin of many spe- 
cies of Aphis, Chermes, and Coccus, and in which the 
eggs of the latter are often involved, may perhaps be 
of use to them in this view; either concealing them 
—tfor they look rather like little locks of cotton, or 
feathers, than any thing animated—or rendering them 
distasteful to creatures that would otherwise prey upon 
them.—The same remark may apply to the slimy cater- 
pillars of some of the saw-flies (Tenthredo. L., T. Cerasi, 
Scrophularia, §c.). The coat of slime of these animals, 
as Professor Peck observes, retains its humidity though 
exposed to the fiercest sun.—Under this head I shall 
also mention the phosphoric insects: the glow-worm 
(Lampyris); the lantern-fly (Fulgora); the fire-fly (Ela- 
ter); and the electric centipede (Scolopendra electrica, Jes); 
since the light emitted by these animals may defend them 
from the attack of some enemies. Mr. Sheppard once 
noticed a Carabus running round the last-mentioned in- 
sect. when shining, as jf wishing but afraid to attack it. 
* Nat. Hist. of the Slug-worm, 7. 
