Page:Popular Science Monthly Volume 89.djvu/109

 Insect Carpenters and Masons

��By Kdwaid I"', liiyclow

��THE NDimi; naturalist who lies face downward at tlic brookside, and with shaded eyes watches the busy life that there has its being, will see, in many places, little masses of small stones or bundles of small sticks, moving on the bottom of ciuiet pools as though they were alive. When out of the watiT they seem to be only groups of stones or clusters of sticks, motionless and dead. But they are the homes of living lar\ae. By putting them in water or by pulling them apart, a whitish habitant is discovered — a larva which is a dainty morsel much relished by fish. Nature has provided it with an ingenious means of protection. The little caddis fly larva is an exemplification of the old saying that "necessity is the mother of inven- tion," since the little animal does not always build as his ancestors built but adapts himself to the circumstances of a new environment and utilizes whatever material may be available. In some localities the cases are made of stones; in others of short twigs; in still others, some of the little builders and mechanics

���Little masses of small stones or clusters of sticks, motionless and dead, are the homes of the caddis fly larvae much rel- ished by fish. These tiny dwell- ings actually move about as if alive in the water, but show no signs of anima- tion on dry land. It is a difficult mat- ter to induce the larva to leave his safe retreat

��bori- out the interior of a slender twig or straw and use the hollow as a protection against the enemy fish.

When caddis flies are placed in small atjuaria they extend the bcjdy out of the Iront of the protecting case and carry it as they crawl. Hut jar the receptacle and the larva instantly retreats into its house. It is hardly possible to pull the little creature out of its case, except possibly from the smooth straw. It clings to its covering with peculiar tenacity by means of two hooks at the rear extremity of the body. So firmly is it anchored to the sticks that violence will not dislodge it, unless the force is sufficiently great to pull the insect in two. But the larva may be driven out by using a tiny toothpick with a blunt end, or by anything else of the kind that does not terminate in a sharp point. Push this into the rear of the case and the little animal at once unhooks himself and hastens out to find a new home.

Usually the cases are straight but sometimes they are curved, and a few spiral forms have been found, which closely resemble minute snail-shells. The dweller in this rude retreat is a tisherman who not only builds a home of sand but uses the sand to make a fimnel-shapcd trap faced by a silken net. The funnel is directed upstream. At the entrance the net has almost rectangular meshes, often in beautiful regulari- ty, and appears nuich like a deli- cate spider wel) in the water. This ingenious contriv- ance is placed in

��95

�� �