How cranefly larvae breathe

Abstract

Aeropyles in the spiracles of the larvae of the terrestrial Tipula paludosa and the aquatic but air-breathing Pedicia parvicellula and an unidentified Tipula are illustrated. In T. paludosa these aeropyles are present and open throughout larval life and through the pharate pupal phase. By contrast, the aeropyles of the aquatic T. sacra and T. abdominalis are essentially closed and, in T. sacra at least, appear not to function during the larval stage. Gas exchange must be effected cutaneously in these latter species and, in T. sacra, the spiracular lobes and perhaps the smaller lobes along the body are principal sites of oxygen uptake. However, the larval spiracles of T. sacra do function during the terrestrial pharate pupal phase, when the central scar plug of the spiracle breaks down. Tipula paludosa has a well-developed "tracheal lung" emanating from the spiracular atrium, but this is absent in T. sacra. It is suggested that this lung functions as a tracheal gill when terrestrial habitats become flooded.