THERMOREGULATION OF THE EXTRARETINAL PHOTORECEPTOR APPARATUS IN THE YELLOW STRIPES OF THE GASTER OF HORNETS

This article describes a system in hornets which presumably serves in thermoregulation of the bases of extraretinal photoreceptors on the in terior surface of the gaster segments. The system is comprised of an a ir sac acting as a bellows and of primary and secondary tracheal ducts which pass along a series of photoreceptors and wind around the base of each photoreceptor to form individual tracheal loops. The respirato ry rate changes in accordance with the ambient temperature and the phy siological needs, so that within narrow limits, efficient thermoregula tion is enabled by the conduction of air at the appropriate temperatur e. The temperature of the conducted air is determined in situ by a pro cess whereby accumulating electric energy in the cuticle is converted to thermal energy by a p-n junction system. Additionally the membrane around the tracheae contains openings through which a product of an ol factory gland is evaporated, that apparently serves as a thermoregulat ory pheromone.