iv. We are now to consider the _clothing_ with which larvæ are furnished. Many are quite naked, and smooth or rough only with granular elevations or tubercles orderly arranged; but a very considerable number, especially of the _Lepidoptera_ order, are clothed with hair or bristles of different kinds, in greater or less abundance, and arranged in different modes; and a proportion still smaller have their skin beset with spines or a mixture of spines and hairs. Lyonnet found that the hairs of the caterpillar of the great goat-moth (_Cossus ligniperda_) were hollow, though not to the apex: probably this is the case with those of other larvæ, as well as with their spines. In this instance they were set, he observes, in a corneous ring, or very short cylinder, elevated a little above the skin. The hair passes through this ring, and appears to be rooted in a soft integument, which clothes the skin within, and upon which the nerves form a reticular tissue, some of which he thinks he has even seen enter the root of the hairs, which perhaps are organs of touch[416].
Of the pilose larvæ, some, like most of those of the smaller moths (_Geometra_, _Tortrix_, _Pyralis_, &c.), have merely a few scattered short hairs, scarcely perceptible except through a lens: others (_Odenesis potatoria_, _Lasiocampa Rubi_) are covered with down more or less thick: in others (_Eriogaster lanestris_, _Lasiocampa Neustria_) the hair is slenderer, and more like wool; the body of two species which I purchased from the collection of Mr. Francillon is covered with woolly hairs, so long as to give them the appearance of a shock-dog; and Madam Merian has figured a similar one, which she could not bring to the perfect state[417]. The hairs of many _Bombycidæ_, known commonly by the name of _hairy caterpillars_, as _Arctia erminea_, &c. are stiffer, resembling bristles; sometimes, as in _Arctia chrysorhea_, mixed with shorter ones. The hairs either spring immediately from the skin (_Noctua Aceris_, _leporina_), or, as is more general, proceed only from certain tubercular elevations, usually subhemispherical, but sometimes conical; of which a number varying from four to twelve are found on each segment of different species. They seem to issue from these tubercles, as little diverging streams from the rose of a watering-pot. In both cases, they form a coating usually so dense as to conceal the body, but sometimes more thinly set, and admitting the skin to be seen more or less between them. In a caterpillar of the beautiful _Arctia ocularia_, the hairs are set upon tubercles alternately nearer the anterior and posterior margin of each segment, so as to form a dense band, the rest being naked; and in the lovely green and black one of _Saturnia Pavonia_, each tubercle bears but six hairs, diverging like a star, the central one being the longest and capitate, so that the chief part of the body appears naked. This diverging position of the hairs is most common in the thick-clothed larvæ also, but many have them placed differently: thus, in those of _Callimorpha Caja_ and _Arctia villica_[418] they are all directed towards the tail, like the quills of a porcupine: in some others the anterior ones point towards the head: in that of _Eriogaster Quercus_ half of the tuft of hairs of each tubercle is directed downwards, the other half upwards: in that of _Arctia Salicis_ all the hairs point downwards, so that the belly is thickly covered, while the back is bare. Another variation is, that the hairs of half the tubercle are sometimes very long, while those of the other half are very short, and even of a different colour[419]. In the larva of Tussuck moths (_Laria pudibunda_, _fascelina_, &c.) the hairs are collected into tufts of a singular appearance, those on the intermediate segments of the back being quite level at the top, so as to resemble so many brushes; while those on the first and last segments are longer, and composed of feathered hairs converging to a point at their extremity, like a common camel-hair-pencil[420]. This last mode of arrangement prevails also in the larva of _Noctua Aceris_; but in this the pencils are shorter, exactly wedge-shaped, and distinguished by another particularity, that of springing directly from the skin, and not from a tubercle. This is also the case with the large caterpillars of _Odenesis potatoria_, which has a double row of short bundles of black hairs on the back, intermixed with larger ones: at each end of the body is a pencil of converging hairs, and the sides are spotted with bundles of white ones, which with longer tawny ones are bent downwards, so as to cover the sides of the creature[421].