CUTICULAR HYDROCARBON SYNTHESIS IN RELATION TO FEEDING AND DEVELOPMENTAL STAGE IN NYMPHS OF BLATTELLA-GERMANICA (DICTYOPTERA, BLATTELLIDAE)

The patterns of hydrocarbon synthesis and transport to the epicuticle were examined in males and females of the German cockroach, Blattella germanica (L.), during the last nymphal stadium. Methods used to extra ct hydrocarbon from insects were validated in detail. A double hexane extraction for cuticular hydrocarbons and a triple chloroform-methanol extraction of homogenized insects for internal lipids removed essenti ally all hydrocarbon from the respective compartments, whereas the ext ernal extraction did not remove hydrocarbon from the interior of the i nsect. Synthesis in vivo was measured by the incorporation of [1-C-14] propionate into methyl-branched hydrocarbon at 2-d intervals throughou t the stadium. In both sexes, hydrocarbons were synthesized at increas ing rates during the first 2/3 of the stadium, then synthesis ceased 2 d before the imaginal molt. Hydrocarbon synthesis was related to stag e-specific food intake in both male and female nymphs. A declining pro portion, but relatively constant quantity, of newly synthesized hydroc arbon was transported to the epicuticle as the nymph progressed throug h the intermolt period. The majority of the newly synthesized hydrocar bon at all ages was retained internally, however, suggesting that they serve as a source of epicuticular and ovarian hydrocarbon in the adul t. Gas-liquid chromatography confirmed the patterns of hydrocarbon syn thesis and showed a greater accumulation of hydrocarbons internally th an on the nymphal epicuticle. Early in the last stadium, the majority of internal hydrocarbon is in the hemolymph, whereas late in the stadi um the fraction of internal hydrocarbon in the hemolymph declines, pre sumably as newly synthesized hydrocarbon begin to associate with fat b ody and the developing imaginal cuticle.