MEANS OF DEFENCE OF INSECTS. 409° 
a defensive armour to them. Madame Merian has figured an enormous 
caterpillar of this kind, — which ane oY she could not trace to the 
erfect insect, — by the very touch of which her hands, she says, were in- 
flamed, and that the inflammation was succeeded by the most excruciating 
aint The vesicatory beetles, likewise (Cantharis vesicatoria, &c.), are not 
improbably defended from their assailants by the remarkable quality, so 
useful to suffering mortals, that distinguishes them. 
Your own observation must have proved to you, thatinsects often escape 
great perils, from the crush of the foot, or of superincumbent weights, by 
the hardness of the substance that covers great numbers of them The 
elytra of many beetles of the genus Hister are so neurly impenetrable, that 
it is very difficult to make a pin pass through them ; and the smaller stag- 
beetle (Dorcus parallelipipedus) will bear almost any weight — the head. 
and trunk forming a slight angle with the abdomen— which passes over it 
upon the ground. Other insects are protected by the toughness of 
their skin. A remarkable instance of this is afforded by the com- 
mon forest-fly (Hippobosca equina), which, as was before observed, can 
searcely be killed by the utmost pressure of the finger and thumb. 
The involuntary secretions of these little beings may also be regarded as: 
means of defence which either conceal 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 envelope the larva of a small hemipterous insect (Aphrophora 
spunaria), from whose anus it exudes, although it is sometimes discovered 
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 secretion that transpires 
through the skin of Zriosoma?, 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 anything 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 (Selan- 
dria Cerasi, Allantus Scrophularie, &c.). The coat of slime of these ani- 
mals, as Professor Peck observes’, retains its humidity though exposed to. 
the fiercest sun. Under this head I shall also mention the phosphoric in- 
sects: the glow-worm (Lampyris); the lantern-fly (Fulgora) ; the fire-fly. 
(Elater) ; and the electric centipede (Geophilus electricus) ; 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 insect, when shining, as if wishing, but afraid to attack it. 
Vatious insects, doubtless, find the wonderful vitality* with which they. 
1 Insect, Surinam. t. 57. Tio different species of caterpillars apparently related 
to this of Madame Merian were in the late Mr. Francillon’s cabinet, and are now i 
MY possession. 
2 To this genus belongs the apple Aphis, called A. lanigera. 
5 Nat. Hist. of the Slug-worm, 7. 
4 The penetrating genius of Lord Verulam discovered in a great degree the causes 
of this vitality. “'Phey stirre,” says he, speaking of insects, “a pone while after 
their heads are off, or that they be cut in pieces; which is caused also for that their 
vital spirits are more diffused thorowout all their parts, and lesse confined to organs 
than in perfect creatures.” Sylv. Sylvar, cent. vii. § 697. 
