Experiments upon respiration in the larvæ of certain parasitic hymenoptera

Abstract

The method by which an apneustic endoparasitic insect larva obtains its oxygen and eliminates the carbon dioxide produced has long been a subject for speculation. Many parasitic larvæ are characterised by the possession of long “tails,” or other expansions of the body wall, and the tendency in the past has been to ascribe to such structures, whether in parasitic or aquatic forms, the function of gills; tracheal gills if they contain tracheæ; blood gills if they do not. Direct evidence as to the function of such structures is scarce, even concerning aquatic forms, and is almost completely lacking with regard to parasites. The work here described was undertaken in the hope of throwing some light on the matter with special reference to the two most striking instances, namely the “tail” of young endoparasitic Ichneumonid larvæ and the “caudal vesicle” of the larval Braconids. The results of similar experiments on a remarkeble Dipterous parasite, Cryptochætum iceryæ , have already been published (Thorpe, 1930). It is hardly necessary to discuss the previous work on the subject and its relation to more general problems, since Wigglesworth (1931) has recently published an excellent summary of the literature dealing with insect respiration.