Edward F. Bigelow, The Guide to Nature, vol. 6, Arcadia Connecticut, Agassiz Association, 1913, pp. 378- 379.
A Little Larva’s Remarkable Masonry
Among the funny things of nature few are more enjoyable than the activities of the tiny insect larva know as a caddis worm and found in brooks and small ponds. This little insect larva builds a case around itself from one -half to three- quarters of an inch in lenght and utilize any material that it can find, sometimes bits of grass, small twigs, shells, but more frequently, in the brooks,grains of sand. The remarkable fact is that the case is built around the caddis worm and presumably as the caterpillar builds its cocoon around itself. The interesting question is, when the caddis fly larva is on the inside how does it fit together the stones that around it ? In the accompanying photo-micrographs- that is, photograph made through a microscope- of some of these caddis worms cases, it will be seen that the seen that the « rocks » are fitted together and cemented as cleverly and skillfully as a stone mason could do the work on a larger scale. One of the case loks as if a microscopic mason had chiped off the stone to make it fit. But the little caddis fly has not done that. It has selected from among the tiny sand grains of the brook such as would fit in and make a neat sans grain patchwork around its body. Here enter the interest and our wonder ar the skill of the larva, but if our young people wish to to make a funny experiment, punch out of these cases a few of the occupants, putting the naked little creatures among other materials, from which they can build other cases. Tiny pieces of broken glass or, better perhaps, very small beads may be put in the bottom of the basin of water and the caddis larva, if conditions are favorable, will build another home with the materials supplied.
Do not try to pull the caddis worm out of its case. It has the rear of its body two hooks that are fastened firmly into the lower part of the case. If you pull from the upper part you may pull the larva in two, before it will let go with the hooks. The successful method is to punch the insect gently from the rear with some finely pointed instrument as, for example, a slender toothpick. The larva, surprised that an intruder is attacking it from the rear, lets go with the hooks and crawls out quickly. Sometimes a series of these cases may be built by one caddis it it is supplied successively with different kinds of materials. the editor has been studying these cases for many years and desires the young folks to cooperate with him, that a collection may be made of the various forms.