Inorganic ion composition of haemolymph of the cecropia silkmoth: changes with diet and ontogeny

The levels' of sodium, potassium, magnesium, calcium, chloride, trehalose, and osmotic pressure in haemolymph were studied during ontogeny in the silkmoth Hyalophora cecropia, reared on either foliage or an artificial diet. Potassium and calcium in haemolymph changed little with ontogeny or diet, and averaged 35 and 10 m-equiv/l., respectively. The haemolymph levels of sodium and chloride were greater in larvae fed on artificial diet than in those on foliage, reflecting the levels in the respective diets; after cessation of feeding, the levels in haemolymph of the two groups approached common values (sodium 1–2 m-equiv/l.; chloride 20 m-equiv/l.). Magnesium was higher in haemolymph of foliage-fed larvae (100 m-equiv/l.) than in diet-fed larvae (65 m-equiv/l.), and in both groups declined after spinning to an average level of 40 m-equiv/l.Haemolymph from fifth instar Manduca sexta larvae reared on an artificial diet had ion levels very close to those in Cecropia similarly reared. Haemolymph of Danaus plexippus at three stages of development was also similar, but showed some quantitative differences from the other species.