Active regulation of insect respiration

Neurohormonal regulation of insect breathing has been studied in the pupae of Lepidoptera, Coleoptera, and Diptera and in the adults of Hymenoptera. The measurements were obtained by a combination of several electronic methods (barographic, anemometric, respiro-graphic, gravimetric, thermographic, infra-red radiation). It has been found that tin contrast to general theories that claim that insect respiration is based on passive physical diffusion) insects can actively breathe through individual spiracles. A lepidopteran pupa for instance, is able to inspire simultaneously through both the contralateral spiracles of a given segment. but it can also use only 1 of them or, eventually, it can exhibit a concert of perfectly coordinated spiracular functions across different segments as well as across different sides of the body. This type of active breathing is regulated by the autonomic nervous system (coelopulse) by means of periodically repeated extracardiac pulsations in hemocoelic pressure. The valves of the selected spiracles pulsate in synchrony with the frequency of extracardiac pulsations, which produce a unidirectional ventilatory stream of air Active, neurohormonal regulation has been also determined for the release of CO(2) from internal carbonate buffers. The pupae of Galleria mellonella (L.), for instance, actively produce gaseous CO(2) only in special, newly identified organs, from which the concentrated CO(2) is rapidly expelled through just 1 or a few selected spiracles. The discontinuous ventilation cycles are usually very simple. The prolonged constriction of spiracles after the CO(2) burst occurs only in certain lepidopteran pupae, whereas the mysterious "fluttering" phase does not exist at all. A possibility that insects favor active regulation of breathing to minimize respiratory water loss and avoid respiratory acidaemia is discussed.