[Illustration: FIG. 48, Larva of Moth (_Agrotis suffusa_), after Packard. 49, Larva of Beetle (_Haltica_), after Westwood. 50, Larva of Saw-fly (_Cimbex_), Brischke and Zaddach. Beob. ub d. arten. der Blatt und Holzwespen, Fig. 8. 51, Larva of _Julus_. Newport, Philos. Transactions, 1841.] Thus, then, although it can be demonstrated that perfect insects, however much they differ in appearance, are yet reducible to one type, the fact becomes much more evident if we compare the larvæ. M. Brauer[58] and I[59] have pointed out that two types of larvæ, which I have proposed to call _Campodea_-form and _Lindia_-form, and which Packard has named Leptiform and Eruciform, run through the principal groups of insects. This is obviously a fact of great importance: as all individual _Meloës_ are derived from a form resembling Pl. 2, Fig. 2, it is surely no rash hypothesis to suggest that the genus itself may have been so. [Illustration: FIG. 52, _Agrotis suffusa_ (after Packard). 53, _Haltica_ (after Westwood).] [Illustration: FIG. 54, _Cimbex_, Brischae and Zaddach. l.c. T. 2, Fig. 9.] [Illustration: FIG. 55. _Julus_ (after Gervais).] Firstly, however, let me say a word as to the general Insect type. It may be described shortly as consisting of animals possessing a head, with mouth parts, eyes and antennæ; a many segmented body, with three pairs of legs on the segments immediately following the head; with, when mature, either one or two pairs of wings, generally with caudal appendages I will not now enter into a description of their internal anatomy. It will be seen that, except as regards the wings, Pl. 4, Fig. 4, representing the larva of a small beetle named _Sitaris_, answers very well to this description. Many other Beetles are developed from larvæ closely resembling those of _Meloë_ (Pl. 4, Fig. 2), and Sitaris (Pl. 4, Fig. 4); in fact—except those species the larvæ of which, as, for instance of the Weevils (Pl. 2, Fig. 6), are internal feeders, and do not require legs—we may say that the Coleoptera generally are derived from larvæ of this type. I will now pass to a second order, the Neuroptera. Pl. 4, Fig. 1, represents the larva of _Chloëon_, a species the metamorphoses of which I described some years ago in the Linnean Transactions,[60] and it is obvious that in essential points it closely resembles the form to which I have just alluded. The Orthoptera, again, the order to which Grasshoppers, Crickets, Locusts, &c. belong, commence life in a similar condition; and the same may also be said of the Trichoptera. The larvæ of Bees when they quit the egg are entirely legless, but in an earlier stage they possess well-marked rudiments of thoracic legs, showing, as it seems to me, that their apodal condition is an adaptation to their circumstances. Other Hymenopterous larvæ, those for example of _Sirex_ (Fig. 9), and of the Saw-flies (Fig. 50) have well-developed thoracic legs.