Richard L. E. Ford, Pond Life, Londres, A. & C. Black, 1964, pp. 47-48.
It has six legs, all outside when the larva is feeding, but it can withdraw into its case for protection. These larvae feed on vegetable matter but there are other species in this order which are free living and do not make cases, and feed on small animal and other insect life. If you remove a case-bearing caddis larva from its home and place it in a tumbler of water along with small fragments of coloured glass, or even coal dust, it will use these to construct a new home. There is an interesting case shown opposite which was formed naturally from empty water-snails shells.