Percival W. Westell, British Insects (General), Ill. Doris Meyer, Londres, The Abbey Nature Books, Chapman & Dodd, circa 1925, p. 74.
The eggs are laid in water, and the larva, soon after hatching, prepares for itself a case, or tube, in which its soft, grub-like body can be protected. Sometimes these cases are made of small pieces of sticks or leaves, at others they are composed of fine grains of sand glued together. Others bear upon them small water-snails in which their owners are also contained, the tube nicely fits the larva, and is just a little longer each end than the creature’s own body. The tail end appears to be sealed up, but the front door remains open until such time as the larva is ready to pupate.