MEANS OF DEFENCE OF INSECTS. 225 



The involuntary secretions of these little beings may 

 also be regarded as means of defence, which either con- 

 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-spit- 

 tle, but which, if examined, will be found to envelop 

 the larva of a small hemipterous insect (Cercopis spuma- 

 ria\ from whose anus it exudes, although it is some- 

 times discovered even in this concealment by the inde- 

 fatigable wasps, and becomes their prey, serves to pro- 

 tect 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 cot- 

 tony secretion that transpires through the skin of My- 

 zoxyla*, and some species of 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 for 

 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 caterpillars of 

 some of the saw-flies ( Tenthredo Cerasi, Allantus Scro- 

 phularia &c.) The coat of slime of these animals, as 

 Professor Peck observes 5 , 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 

 (Elater); and the electric centipede (Geophilus electri- 



a To this genus belongs the apple Aphis, called A. lanigera. 

 b Nat. Hist, of the Slug-worm, 7. 



VOL. II. O 



