Caddis-Worms. 205 



cases, is superior to pozzolana * in standing water, in which 

 it is indissoluble. The grubs themselves are also admirably 

 adapted for their mode of life, the portion of their bodies 

 which is always enclosed in the case being soft like a meal- 

 worm, or garden-caterpillar, while the head and shoulders, 

 which are for the most part projected beyond the door-way 

 in search of food, are firm, hard, and consequently less liable 

 to injury than the protected portion, should it chance to be 

 exposed. 



We have repeatedly tried experiments with the inha- 

 bitants of those aquatic tents, to ascertain their mode of 

 building. We have deprived them of their little houses, 

 and furnished them with materials for constructing new 

 ones, watching their proceedings from their laying the first 

 stone or shell of the structure. They work at the commence- 

 ment in a very clumsy manner, attaching a great number of 

 chips to whatever materials may be within their reach with 

 loose threads of silk, and many of these they never use at 

 all in their perfect building. They act, indeed, much like 

 an unskilful workman trying his hand before committing 

 himself upon an intended work of difficult execution. 

 Their main intention is, however, to have abundance of 

 materials within reach : for after their dwelling is fairly 

 begun, they shut themselves up in it, and do not again 

 protrude more than half of their body to procure materials ; 

 and even when they have dragged a stone, a shell, or a chip 

 of reed within building reach, they have often to reject it as 

 unfit. (J. E.) 



[We have here some examples of the latter kind of nest, 

 i. e., those habitations which are made of stones and shells. 

 Beginning at the upper left-hand figure, we find one that is 

 made of moderately-sized stones cemented together in a way 

 that reminds the observer of the manner in which a builder 

 forms irregular stones into a wall. Next to it is another, in 

 which the stones are larger and narrower, and are arranged 

 much as some of the caddis-worms arrange pieces of stick and 

 straw. 



* A cement prepared of volcanic earth, or lava. 



