THE CABBAGE BUTTERFLY. 91 



wings. Powerful wing muscles are to be developed 

 within them. 



Kill a large larva by placing a drop of chloroform upon 

 its head, or by any other convenient method, and with a 

 good lens examine : 



1. Its head, as seen from 

 the front and from be- 

 neath. Make out : 



(a) Ocelli situated on 



the front of the lateral DIAGRAM OF LARVA (x 2): e, simple 



prominences of the head. f es . ? n , ^ f nt f * a h f d; 



* I, ]omted legs attached to the three 



How many, and how ar- thoracic segments; sp, spiracle 



ranged? openings; pr, prolegs. 



(5) A labrum, a little flap of membrane above the mouth. 



(c) A pair of rather prominent biting mandibles which 

 meet by serrated edges. 



(d) On either side of these a very rudimentary stump 

 of an antenna, here found situated lower on the head than 

 in the perfect insect. 



(e) Below the mandibles, a pair of very rudimentary 

 maxillce. They are but fleshy prominences here, made 

 recognizable by a pair of minute appendages (palpi) at 

 the tip of each. 



(/) Between and below the maxillae is the larger la- 

 brum with its very minute rudiments of palpi, and a 

 median appendage of special structure (a slender horny 

 tube, which serves as a spinneret) . Through it is exuded, 

 from glands in the head, a liquid, which dries, immediately 

 on exposure to the air, into the silken thread which the 

 larva spins over the leaves. 



Compare this mouth with that of an adult. 



2. The covering of the skin. What kind of out- 

 growths can you find with a lens ? 



3. Its thoracic legs. Make out : 

 (a) That they are jointed. 



