Larvae and their Work 



the case may be. Another common species places short 

 lengths of stick transversely across one another, and fastens 

 them together to form its spiky home. A third constructs 

 a house of small shells, some of which still contain their 

 owners who are carried about willy-nilly by the caddis 

 larva. Still another builds a tube of fine sand. 



As this list could be continued to considerable lengths, 

 let us mention a little point of interest before describing 

 two of the most extraordinary larval houses to be found 

 amongst these adept house-builders. The caddis larva 

 must needs be something of an engineer, or should we say 

 a physicist, as well as a builder. His home must be light 

 enough to be moved freely from place to place, yet not so 

 light that it will float in water. An examination of a few 

 of these larval cases will show some which are absolutely 

 ruined from an architectural point of view. 



Beautifully built, in the main, of sticks, or shells, or 

 pebbles, or sand, or whatever material is most favoured by 

 the particular kind of larva, each item in the structure 

 being of approximately the same size as all the others, 

 yet the whole appearance of the case is spoiled by the 

 fact that a large pebble or shell is affixed to one side of 

 the case. These eyesores are not without their uses : they 

 serve as ballast for the caddis home ; they prevent the 

 little building from floating to the surface of the water. 



And now for the more ingenious caddis dwellings. 

 There is one kind of larva which, forsaking the conventional 

 tubular case, builds one of sand exactly like a snail shell 

 in appearance. So close is the resemblance between the 

 homes of these two quite unrelated creatures that the 

 caddis dwelling for long puzzled naturalists, one of whom 

 actually described it as a new kind of snail. Curiously 

 enough, the home of a minute marine worm closely mimics 

 a snail shell ; this little creature is often found in hundreds 

 attached to the common bladder wrack. 



The second dwelling we are about to describe is more 

 ingenious though no more curious. Everyone has either 

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