Respiratory efficiency of the larva of the caddis fly Triplectides obsoleta McLachlan (Trichoptera, Leptoceridae). 1. Respiratory movements

Abstract

Ross (1964) described five basic types of trichopteran larvae, free living, net builders, saddle case builders, purse case builders and tube case builders. Morphologically the three types of case builders, saddle-, purse- and tube- demonstrate progressive consolidation of the anal claws and hooks, culminating in the two anal hooks directed laterally and anchoring the insect in its case at the opposing mid-lateral points. Ross argued that the evolution of the Trichoptera began with free living larvae, much like the present-day Families Rhyacophilidae and Philopotamidae, which have largely colonized swift-flowing mountain streams rich in dissolved oxygen, and the subsequent development of the group has included the acquisition of adaptations which have enabled the larvae to colonise lentic and lotic habitats, environments characterized by higher temperatures and progressively more anaerobic conditions. Such larvae generally construct cases made of carefully selected materials bound together with silk, which serve not only for protection, but also as a means of ventilating the abdominal tracheal gills. Rhythmic undulations of the abdomen can be used to take water in through the front of the case and expel it through the back, thus increasing the gradient of oxygen concentration across the gills.