Jack in the green

Anonyme, « Nature Notes », The Selborne Magazine, Londres, vol. 17, The Selborne Society’s Magazine, John Bale & Sons & Danielsson, janvier/ février 1906, p. 21-22.

This was the second week in October, and early in November we noticed that the water was swarming with microscopic creatures, which proved to be the larvae of the caddis fly. Minute as the creatures then were, they had ensconced themseves in dainty castles of beautiful and delicate mosaic work, made by cementing tiny grains of sand edge to edge. The little caddises had bright mahogany-coloured heads with enormous eyes, and their seix legs, which during locomotion, they protruded from the mouth of their castles were covered with hooked bristles.

Day by day we watched as they scrambled over the water-weed and fed on it, after the manner of ordinary caterpillars. In the early stages, when not feeding, they amused themselves by clambering up the glass walls of the aquarium and tumbling down again.

By january 12 their castles were about an eighth of an inch in length, and on that date we pounded up a small portion of nacre from a pearl-oyster shell and put it into the aquarium with the sand. The next day nearly every caddis case had a narrow rim of mother-of-pearl arranged round the wide end, and the addition gave a perfectly artistic touch to the whole.  After this the sand was forsaken for building purposes, except in four solitary cases. Of these one caddis was particularly conservative and kept to the sand ; two build the under part of sand, and that part which covered the back of mother-of-pearl ; and another ignored both sand and pearl, and,  using bits of waterweed, appeared as a veritable « Jack in the Green. »

At first the cases were so transparent that the waving motion that the waving motion of the body within could be quite clearly discerned. Later the movement was more obscured, and at last entirely hidden, perhaps by the thickness of the gluten and silk with which each case was lined. In the early morning the sand at the bottom of the aquarium was etched with a maze of lines caused by the caddises walking round and round and dragging their castles after them. Up to mid-day they seemed to do nothing but perambulate the the sand in a ridiculously serious manner, excet occasionally one would halt, forage in the sand for a second or two, and then pass on. Assiduously as we watched the little creatures, we were never once fortunate enough to see them in the act of cementing fresh bricks to their castles. This was evidently the work of the night, for in the morning we were often able to detect where new material had been added to several of the cases. Of all the myriads which swarmed in the water in in the early stages, only about two dozen arrived at maturity; but this was an advantage, in that it enable us to single out individuals and upon them concentrate our observations.