Epicuticular Hydrocarbon Composition of Wild and Laboratory-reared Drosophila mojavensis Patterson and Crow (Diptera: Drosophilidae)

Abstract

Epicuticular hydrocarbons of Drosophila mojavensis (Patterson & Crow) were identified and quantified as a preliminary to an investigation into the involvement of epicuticular hydrocarbons in the behavioral and physiological ecology of catiphilic Drosophila Epicuticular hydrocarbons of D. mojavensis contain 23 to 39 carbon atoms, with >96% of the total hydrocarbon containing 29 to 37 carbons. Odd-chain lengths predominate. Alkanes consist almost entirely of C 29 , C 33 2-methyl-branched molecules. Alkenes are mostly C 31 to C 37 and are unusual in that a significant proportion consist of methyl-branched molecules. The n-alkenes are mostly (Z)-10- and (Z)-12-, but lesser amounts of (Z)-9-, 13-, 14-, 15-, and 16- also occur. The 2-methyl-branched alkenes are predominantly (Z)-8-, 10-, 12-, and 14-. The predominant alkadiene positional isomers (7,23- and 8,24-C 33.2 , 7,25- and 8,26- C 35.2 , 7,27- and 8,28-C 37.2 ) represent a symmetric arrangement of double bonds that has not heretofore been reported for insects. Ontogeny is accompanied by a doubling in total hydrocarbon per fly, primarily because of increases in the amount of alkadienes. Sexual dimorphism in epicuticular hydrocarbon profile was detected in the percentage abundance of many components and in the relative amounts of C 35.2 and C 37.2 . Ontogenic patterns for many individual hydrocarbon components also are sexually dimorphic. Flies in nature have significantly less total hydrocarbon than laboratory-reared flies and differ in the relative amounts of several olefinic components as well, leading to the suggestion that epicuticular hydrocarbon synthesis and deposition in wild flies may be affected by compounds in the rotting tissue of their host cacti. Finally, we suggest that insect chemosystematic studies using epicuticular hydrocarbon might take advantage of the diversity in olefin positional isomers that apparently exists in a number of insect groups