Colouring Matters of the Aphidoidea. XLIV * A Survey of Long-Chain Acid Derivatives from Aphid Lipids Compared with Those of Related Insects. Glycerides of Octa-2,4,6-trienoic Acid

A comprehensive survey of lipids representing all families of the Aphidoidea and several related families supports the chemotaxonomic separation of aphids and coccids from the remainder of the Hemiptera. Aphid glycerides are based chiefly on myristate, palmitate and sorbate as noted earlier; octa-2,4,6-trienoate residues are reported for the first time. In Part XXV1 Bowie and Cameron examined the fatty acid residues from a limited number of aphid triglycerides and noted two distinct differences from those of other insects. In agreement with an earlier survey2 their dominant chain length corresponded to myristate or, occasionally, to palmitate, derivatives of eighteen-carbon acids being present to only a limited degree. In addition, they often contained sorbate, a constituent that has been found nowhere else in the animal kingdom. Thus 1,3-dimyristoyl2-[(E,E)-sorboyl]glycerol (1) was by far the major lipid of the aphid Dactynotus jaceae. These unusual features do not appear to apply to the fatty acid residues in aphid phospholipid^.^