EASTERN UNITED STATES. 19 



THE LAEVA. 



The larva, or caterpillar, is elongated or somewhat 

 worm-like, usually plainly separable into thirteen joints 

 or segments, the first of which is the head. Joints two, 

 three, and four have each a pair of short legs, the 

 rudiments of the legs- of the perfect butterfly. Joints 

 seven, eight, nine, ten, and thirteen have each a pair of 

 membranous legs, the end of each 

 armed with a circle of minute hooks, 

 as seen in Fig. 2. By means of 

 these hooks the larva is enabled to 

 grasp firmly any object which is not 

 too smooth, as the surface of glass. 

 In this case the larva first spins a 



r n ji i ^ opa. a. proieg. .A. **X2J y > 



covering of silk over the glass, and circlet of hooks at end of 

 then walks over it easily. These legs P role g' X f) ; c > one of the 



J hooks, X !2. 



are called prop-legs, or, as it is more 

 often abbreviated, prolegs. These disappear at the close 

 of the larval period, when the larva changes to a chrys- 

 alis. 



On each side of the body are nine oval stigmata, or 

 breathing-pores, often called spiracles. These are situ- 

 ated in joints two and five to twelve inclusive. These 

 stigmata open into a series of air-tubes which ramify 

 through the system, each stigma leading to a single trunk 

 of the system. Close to the origin of this trunk a large 

 air-canal runs along each side of the body, connecting 

 all the trunks of one side. Joints three and four, having 

 no stigmata, receive their branches of the system of air- 

 passages from this trunk. Like the air-passages in the 

 lungs of the vertebrate animals, these tracheae continue to 



