LEPIDOPTERA 109 



ing laterally between them, may readily be seen with a lens. 

 A careful search of the labium with a lens will reveal the 

 pointed tip of the spinning tube at its apex. Out from this 

 the silk secretion is poured in a liquid state, to harden on 

 contact with the air when drawn out into a silken thread. 

 One pair of large glands inside the body secretes the silk 

 and pours it out through the opening. By this means all 

 the suspension lines of the cankerworm, and all the webbings 

 of the tent caterpillars and webworms, and all the cocoons 

 of all the order and all our silk of commerce is spun. Silk 

 is spun only in the larval stage; and most of the spinning 

 is done at the end of larval activity in the making of cocoons 

 and other shelters for transformation. 



The thorax is clearly marked by the possession of jointed 

 legs. The prothorax often bears a horny brown shield above. 

 Spiracles open at the sides of the synthorax. The legs are 

 very short — almost clawlike, but are composed of the usual 

 parts, greatly reduced in length. 



The abdomen is very large, composing in the caterpillar 

 by far the greater part of the body. To support and propel 

 it, fleshy, unjointed prolegs are developed, underneath some 

 of the segments. There are from two to five pairs of these, 

 each bears at its tip a circlet of minute crotchets, that are 

 well adapted for hooking onto the roughnesses of a leaf or 

 into the mesh of a web. 



With the shedding of the last larval skin, the pupa is 

 disclosed. Sometimes it is formed openly, as in most butter- 

 flies, then it may take on the bright tints of green and gold 



