Terpenoids as Insect Repellents

At the time when the earlier review was written the interest in terpenoids in the defensive secretions of insects was more than a little coloured by the then novel chemical structures of compounds such as iridomyrmecin (LXXXV) and iridodial (LXXXVI) possessing the l,2-dimethyl-3-isopropylcyclopentane skeleton, and the question as to whether these compounds represented a new class 

Although differences of interpretation exist as to whether they may not in fact be alerting pheromones [21] rather than defensive agents (especially in instances where the compounds concerned were isolated by solvent extraction of the whole animal without further experiments being conducted to ascertain 

The isolation of the glucoside of cuminaldehyde cyanohydrin (XCVI) from the millipede Polydesmus vicinus L. [732] is of great interest since, like the established function of mandelonitrile in Apheloria corrugata [733-735] it could represent a means of delivery of hydrogen cyanide. 

Recently the sesquiterpene a-farnesene has been demonstrated to be a constituent of the secretion of Dufour s gland in the ant Aphaenogaster longiceps [736], while citral has been shown to serve as a recruiting pheromone when workers of the stingless bee, Lestrimelitta limao, attack the nests of other stingless bees [736 a]. 

Studies of the products of alkaline hydrolysis of shellac, the resinous material used as enteric coating for pills and tablets in pharmaceutics, would perhaps suggest the presence of cedrane-type sesquiterpenoids in insect defensive secretions. Thus shellac, which is formed by heat treatment of the protective 

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