The chemistry of aphids and scale insects

Abstract

A general survey of aphids and scale insects is followed by a review of their secondary metabolites, a few of which may be found in museum artifacts or as conservation requisites. Lac resin (which gives shellac of commerce) is based upon complex oligomers of hydroxy acids joined by ether and ester linkages. In addition to a range of minor constituents, the following hydroxy acids have been found: 9, 10, 16-trihydroxypalmitic acid, jalaric acid, and laccijalaric acid. The last two are tricyclic sesquiterpenic aldehyde-acids. The structures of the actual oligomers remain uncertain. Three scale insect pigments have been important as dyestuffs: cochineal (carminic acid), kermes (kermesic acid) and lac dye. All these insect pigments are anthraquinones, and the structures of carminic and kermesic acids, now well established, are given. Lac dye is a rather complex mixture of (at least) three phenolic compounds (erythrolaccins) and four phenolic acids (laccaic acids). Waxes secreted by certain coccids have been used by many peoples, for example in China, in India and in South America. The chemistry of these waxes is reviewed. Other insect products described include honeydew, manna, and carotene and polycyclic quinonoid pigments from aphids. -- AATA