218 COMMON BRITISH INSECTS. 



never felt sure of them. They were continually 

 escaping. Putting them into a wooden box was quite 

 useless, as they ate their way through the side in a 

 very short time. Putting them in a tin box was 

 equally useless unless the cover were tied down, for 

 they had a way of pushing at the lid round the edges, 

 and so gradually opening it sufficiently to permit their 

 escape. Even perforated zinc is not safe from them, 

 for I have known my caterpillars to find out a place 

 where the zinc has been cracked, fix their short and 

 powerful jaws in the holes, and fairly twist down a 

 flap through which they managed to force themselves. 



When the larva is full-fed it forms a cocoon made 

 of fragments of gnawed wood and silk. The cocoon 

 is very tough, and will withstand much rough hand- 

 ling. These cocoons are oval, similar in shape at 

 both ends, flexible, and yellow in colour, and are very 

 strongly scented with the odour of the insect which 

 made them. There is considerable variety in the size 

 of the cocoons, and some are barely half as large as 

 others. The small cocoons seem never to produce 

 Moths, but are infested by an ichneumon-fly, which, 

 fortunately for us, preys on the Goat Moth caterpillar. 

 Not that the large cocoons are free from this parasite, 

 for, as every one knows who has bred them, the large 

 cocoons frequently disappoint the collector, and pro- 

 duce ichneumons instead of Moths. It is a curious 

 fact that the ichneumon itself (Lampronota setosd} 

 possesses an odour similar to that of the larva in 

 which it lays its eggs. 



After the larva has lain in its cocoon for some 

 time, it discharges from its mouth a fluid which is 



