The Disappearance of Moulting Fluid in the Tobacco Hornworm, Manduca Sexta

ABSTRACT In Manduca sexta, and other insects, moulting fluid (MF) accumulates after apolysis in the exuvial space which underlies the old cuticle, and then most of it disappears shortly before ecdysis (see reviews by Zacharuk, 1976; Jungreis, 1979). Moulting fluid digests and weakens the old endocuticle so that the animal may free itself at ecdysis, and the digested components of the old endocuticle are reabsorbed. In M. sexta, Jungreis (1979) found that MF is produced between 30 and 12 h before the larval-pupal ecdysis (LPE) and it begins to disappear about 9 h before the LPE (LPE –9h). By LPE –3 h, most, but not all, of the MF has disappeared. We have found that MF represents a significant fraction of the total body water, 14·7% body weight (bw) [0·579 ± ·042 (5) ml, mean ± S.E. (N)] at LPE –6h.