252 NATURAL HISTORY OF AQUATIC INSECTS CH. 



The glands arc enormously developed in Caddis- 

 worms, and may be three times as long as the 

 body.] 



"If we remove a Caddis- worm from its sheath 

 without injuring either, and then lay the two side by 

 side, the Caddis-worm at once enters its case, head 

 foremost. It is not so foolish as some other kinds of 

 larvae which fail to recognise their own sheath when 

 they have once left it, and would rather make a new 

 one than put on a second time the covering which 

 has been stripped off them. The front opening is 

 the only one by which the Caddis-worm can enter. 

 As it enters head first, its position is now reversed, 

 but the sheath is sufficiently wide for the Caddis- 

 worm to turn round inside. I have seen a Caddis- 

 worm with its head and limbs projecting as usual 

 from the front opening, by which it had re-entered 

 head first the day before, after being forcibly ex- 

 tracted. 



" Though Caddis-worms will return to their sheaths, 

 it is not because they are too lazy to make new ones. 

 Wishing to see them at work, I took a Caddis-worm 

 in the beginning of April, stripped it of its case, and 

 put it into a glass dish with various bits of leaves soaked 

 in water. In less than an hour it had made a new sheath 

 of fragments of leaves. It is true that the sheath 

 was rather shapeless, and seemed to be made of odd 

 pieces slightly fastened together. However, it served 

 to conceal the body completely, and the Insect could 

 drag it about wherever it went. 



" I turned this Caddis-worm out of its case a second 

 time, as I had not sufficiently observed its mode of 



a 



