THE LARVA 41 



together. The other portions of the cocoon are of compact silk, 

 and anj' insect intruder that ventiu'es to enter b^' what we may 

 ahnost term the open end is met by a number of spikes, as it were, 

 that play on it at every attempt. Many of these wonderful cocoons 

 may be found during the winter months attached to the food plants 

 of this insect. 



Of the silken cocoons spun by various caterpillars some are so 

 thin and light that the chrysalis can easily be seen through them, 

 and others are so densely woven as to be quite opaque. A 

 great difference is also to be observed in the adhesive power of the 

 silk fibres. In some cases little threads of silk can be pulled off 

 the cocoon ; but some of them, that of the Oak Eggar (page 229) for 

 example, look as if they had been constructed of paper rather than 

 of silk, because, at the time of spinning, the moist silk fibres stuck 

 so closely together. 



An extreme case of this character is to be met with in the 

 cocoon of the Puss Moth (page 235) ; for here the fluid from the 

 spinneret of the caterpillar does not harden at once on exposm'e to 

 air, and so the threads become thoroughly united together, thus 

 forming a solid gluey cocoon. 



When the Puss caterpillar is about to change, it descends the 

 tree (poplar, willow, or sallow) till it is within a few feet of the 

 ground. Then it commences gnawing away at the bark, at the 

 same time cementmg all the pieces together with the gluey sub- 

 stance from its spinning glands. In this way it surrounds itself 

 with a very hard cocoon, which so closely resembles the surround- 

 ing bark in coloiu" that detection is difficult indeed. 



But how will the caterpillar proceed if it is removed from its 

 native tree and has no bark to gnaw ? That you can easily answer 

 for yourself, or rather Puss will answer it for you. Go and search 

 among the poplars, willows and sallows in the month of July. You 

 may possiblj^ come across a caterpillar that is just in the act of 

 creeping down the bark in search of a resting ])lace ; but if not you 

 may be successful in obtaining a few either by examining the twigs, 

 or you may start them from their hiding places by smartly tapping 

 the smaller branches with a strong stick. 



Having secured one or more larvae, take them home, and they 

 will give some rather novel performances. If they are not fully 

 grown, you nmst supply them with fresh leaves every day till they 

 refuse to eat ; and then is the time for your experiments. Shut one 

 in a little wooden box, and vou will have the pleasure of watching it 



