STATES OF INSECTS. 139 



which enable the animal to push itself along between the 

 bark and the wood a . 



In considering, in the next place, the number and si- 

 tuation of the prolegs, it will contribute to distinctness to 

 advert to these circumstances as they occur in the diffe- 

 rent orders furnished with these organs. 



To begin with the Lepidoptera. — Lepidopterous larvae 

 have either ten, eight, six, or two prolegs, seldom more b , 

 and never fewer. Of these, with a very few exceptions, 

 two are attached to the last or anal, and the rest, when 

 present, to one or more of the sixth, seventh, eighth, and 

 ninth segments of the body : none are ever found on the 

 fourth, fifth, tenth, or eleventh segments. 



1. Where ten prolegs are present, as is the case in by 

 far the greatest proportion of Lepidopterous larva?, there 

 is constantly an anal pair, and a pair on each of the four 

 intermediate segments just mentioned. 



2. In caterpillars, which like those of a few species of 

 the genera Sphinx, Pyralis, and of the Bombycidce, &c. 

 have eight legs, -they are placed in three different ways. In 

 those which have an anal pair, the remaining six are in 

 some fixed to the sixth, seventh, and eighth ; in others, to 

 the seventh, eighth, and ninth segments. In those which, 

 like Cerntra Vinula, and several other species of the 

 same family, have no anal prolegs; the whole eight 

 emerge from the sixth, seventh, eighth, and ninth seg- 

 ments. 



3. The Hemigeometers, as Noclua Gamma, &c. have 



a See above, p. 110, 114. 



b Some few subcutaneous larvae have more, as that, before men- 

 tioned, observed by Dc Geer in the leaves of the rose ; which has 

 eighteen prolegs, and no true ones. 



