Studies on lipids in some Homopterous insects

Abstract

There is little information available on the occurrence of lipids in aphids or other sucking insects, and little is known of the role of lipids in aphid nutrition. The purpose of the present investigation was to obtain preliminary information on several phases of these problems. The classes of lipids extracted from one aphid, Macrosiphum barri Essig, were separated by column chromatography. The fatty acids in each of these classes as well as in the crude lipid extracts from 20 other species of aphids and six species of leafhoppers were separated by gas-liquid chromatography. Nearly all of the fatty acids in M. barri were in the form of triglycerides, as in other insects that have been studied by previous investigators. The free fatty acids accounted for only a small percentage of the total quantity of lipids extracted from M. barri. In general, aphids had a high proportion of the fatty acids with a carbon chain length of 14 or less and a low proportion of fatty acids with 18 carbon atoms. The reverse was found for the leafhoppers analyzed. The fatty acid composition of an aphid appears to be a species characteristic, not appreciably influenced by the host plant. It changed with the stage of development in some species but not in others. Its possible usefulness in aphid taxonomy is uncertain at present. Fatty acids were found in the honeydew of two species of aphids. Their relative proportions in the honeydew of the green peach aphid and in the juice of its host suggest that linoleic acid may be required in the diet of that aphid.