Arboreal earthworms are scarce in tropical rain forests, being confined to tree trunks or epiphytes (Fragoso & Rojas-Fernandez 1996). Their above-ground presence might be attributed to (1) temporary responses to flooding (Adis & Righi 1989), (2) permanent responses to acidity, flooding and anoxia of very wet forest soils (Lee 1983), (3) drought (Fragoso & Rojas-Fernandez 1996), (4) accidental events, e.g. mudslides (Picado 1911), or (5) anti-predation responses, e.g. escape from army ants (Gotwald 1995).

The chemical nature of the repellent secretion of the African grasshopper, Zonocerus variegatus (Orthoptera: Pyrgomorphidae) reared on Acalypha wilkesiana L. and Manihot esculenta (Crantz) was analysed. It was found to contain alkaloids, glucose, proteins, free amino acids, trypsin-like proteinase, carbohydrases, lipase and the ions Ca2+, Mg2+ and K+ but not Na+ and (PO4)2-. Alkaloids were present in the secretion whether or not the insect was fed on plants containing alkaloids. Cyanide ions were absent in the secretion, even when Z. variegatus was fed exclusively on the cyanogenic Manihot esculenta. The amino acid and glucose contents were the same in grasshoppers reared on different plants. The protein content in the repellent secretion was constant, despite the fluctuations observed in the protein content of the haemolymph.