Jabez Hogg, The Microscope, its History, Construction and Application, Londres, Herbert Ingram & Co., 1856, p. 303.

..these larvae always enclose themselves in cases formed of various materials ; bits of straw and sticks, pebbles, and even small shells, being commonly employed in this manner. The materials of these curious cases are united by means of fine silken threads, spun like those of the caterpillars of the Lepidoptera, from a spinnaret situated on the labium. In increasing the size of its case to suit its growth, the larva is said to add only to the anterior end, cutting off a portion of the opposite extremity.