Anonyme, Children’s museum News, Vol 1-8, New York, Brooklyn Institute of arts and sciences, 1914, pp. 60 -61.
The caddis fly larvae
The small, dark-colored, cylindrical objects in the jar behind the magnifying glass in the Type Room arc larvae of the Caddis Fly. They were found in the pond at Van Cortland Park.
If you watch them for a moment through the lens, you will doubt-less perceive a head, and o thorax with six attached legs emerge from an end of one these tubulars objects. That is all of the inmate that you will be able to see because this creature does not venture further out of his case or house than is necessary to enable him to use his legs while crawling around in search of food. He carries his house with him, holding it securely by means of two hooks at the posterior end of his abdomen. The head and thorax are covered with brown tough chitib, but the portion of the body in the case, is white, soft, and quite susceptible to injury. To protect this delicate part of his body as well as to provide for himself a hiding place, the creature has made use of this peculiar dwelling.
Now where did these insects get their portable houses ? The answer is that each larva constructed his own house out of material which he himself manufactured. In other words, each larva secretes a fluid which, by the action of water upon it, is converted into a kin of silken thread ; and it is this thread which is spin by the larva into a tubular covering. To add strength to the structurer the larva also made use of small pebbles, pieces of wood, or other, or other small objects which were near by.
In this tube the insect will pass through the larva and pupa stages, though as a pupa the creature will cease to come out of the house and will deny himself to visitors by constructing a door across the entrance.
Interesting facts are known regarding the habits of the Caddis Flies. These insects have been observed by several scientists, although their classification has not been definitely determined. However, concerning the Caddis Flies as a group it may be said that they belong to the Order Trichoptera and to the Family Phryganidae. Moth-like, fourwinged insects, they are found all over the United States in the vicinity of fresh water ; either ponds, brooks, or the Swift moutain streams of the Rockies. The adult stage of the insect is brief and not conspicuous for any act except that of reproduction. The matured female deposits the eggs in water or on a stalk of grass growing in water.The adult flies do not eat nor do they live long after the eggs have been laid. It is the larval stage of the insect that is characterized by unique performances. As soon as hatched,the Young begin to spin the tubular cases which are to be their homes. The larvae of some species weave into the silken covering, in addition to small stones or bits of wood, the shells of living snails. The adroitness of the larvae has been manifested by other clever feats.For instance a larva makes his house large rat the front than at the rear, crawls in head first and turns around Inside so that his head may protrude from the large end . He closes the smaller end with a silken flap. As his girth expand, he may build on to the front end of his house and cut off the smaller back end, turning around inside the tube whenever the mechanics of the building opération require the presence of his head in the rear of his apartment.
He makes the tube wide enough to admit the passage of a current of water from which he obtains his air supply. Most of Caddis Fly larvae are herbivorous, but one species is carnivorous if one may judge by its predacious habits. Members of this species are able fishermen. Of silk they spin a little funnel-shaped net which they set between, two stones with the opening up stream. Through this net they can strain from a considerable volume of water small insects and organisms that serve as food.