Duckweed (2)

Hy. B. Guppy, « Caddis-worms & Duckweed » Science-Gossip, Londres, vol. II, n° 13  mars 1895, p. 11.

My attention was attracted last May by the remarkable manner in which some caddis-worms cleared one of my vessels of duckweed (Lemna minor and thin fronds of L. gibba). Five of these creatures disposed of, on the average, twenty plants dally , and I estimated that in a pond covered with duckweed one caddis-worm to every four square inches of the surface would not merely check the growth but in the course of two months would clear the surface of the duckweed altogether. Though most of the plants are eaten , many die from being partially devoured ; and as in the species the larvae construct their cases of the fronds, quantities of the plants are expended in the constant repairs of their homes.