The Respiratory System of Adult Odonata. Part 1: The Spiracles1

Abstract

Adult Odonata possess 10 pairs of spiracles, of which 2 pairs are thoracic, the rest abdominal. Each mesothoracic spiracle has 2 tracheal openings, separated by a septum to which an occlusor muscle is attached. The metathoracic and the abdominal spiracles have only 1 opening. In the Anisoptera each spiracle is provided with an internal closing apparatus and possesses hairs forming a filter apparatus which, in the 11 anisopterine species studied, is best developed in Hemianax. The Zygoptera studied have no closing apparatus for the abdominal spiracles and they lack filter hairs. The first abdominal spiracle shows a distinct shift in position in different forms, and differs also in its orientation.