34 
°Insects are either covered with hair or without 
hair; with slight scales or without them; with horny 
armour or without it ; endued with formidable horns, 
or without them. Of the first, Mr. Kirby observes, 
«J may mention the long hairs, stiff bristles, sharp 
spines, and hard, tubercular prominences with which 
many caterpillars are clothed and studded. That 
these are means of defence is rendered more pro- 
bable by the fact that in several instances the ani- 
mals so distinguished, at their last moult, previous 
to their assuming the pupa, in which state they are 
protected by other contrivances, appear with a smooth 
skin. The powers of annoyance, by means of their 
hair, with which the moth of the fir and the pro- 
cession moth are gifted, are doubtless a defensive 
armour to them. But the most striking instances 
of armour are to be found in the hemiptera order, 
amongst the cicadiadz: of this kind is the cicada 
spinosa, the centrotus clavatus, and centrotus globu- 
laris, so remarkable for the extraordinary apparatus 
of balls and spines, which it appears to carry erect, 
© See Carus, Introduction to Comparative Anatomy, translated 
by Gore, vol. ii. p. 118. One kind of productions from the sur- 
face of the skin which arrives at a high degree of developement 
in the articulata, first presents itself in the vegetable kingdom, 
viz. hair. The dew-worm has small bristles, which serve partly 
as organs of motion. The hair of the nereides, particularly those 
which glitter so abundantly in the aphrodita, is soft and bristly. 
Even in the crustacea, notwithstanding the petrified surface of 
the skin, the hairs do not disappear; we find them evident on 
the edges of the scuta ; on the legs, where they protrude from the 
pores of the shell ; and, above all, on the outermost pair of maxil- 
le in the crayfish, &c. 
