Case building behaviour of the caddis fly larva, Lepidostoma hirtum

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Abstract
On hatching from the egg, a larva of Lepidosroma hirtum Curtis constructed a tubular, sand grain case. As the larva became older it periodically added new material to the anterior of the case and, once in every instar except the 1st, cut off ⅓ to ¼ of the posterior of the case. In the 3rd instar the larva changed from adding sand grains to cutting out and attaching almost rectangular leaf panels. By the 5th instar the case was composed entirely of leaf panels. The case was then square in section and composed of one row of panels for each of the sides. The panels were not truly rectangular but convex on the leading edge and sides and concave at the back, so that the anterior convexity of one panel fitted into the posterior concavity of the panel in front. Panels were arranged with their long axes across the case. The seams between panels in the roof were half a panel length out of phase with those in the sides but in phase with those in the floor. The convex sides of a panel allowed it to overlap the seams between panels on the two adjacent sides. If a 5th instar larva was removed from its case it first built a sand grain case followed by a leaf panel case. The animal cut panels from the leaf with its mandibles and then further shaped them by chewing round the edge. Just prior to pupation, the case was modified by the attachment of further panels to the anterior; these included panels which for the first time in the life of the larva were arranged with their long axes along the case.