The cuticular hydrocarbons of the soil burrowing cockroach Geoscapheus dilatatus (Saussure) (Blattodea: Blaberidae: Geoscapheinae) indicate species dimorphism

Cuticular hydrocarbon analyses of 24 geographical populations of the soil burrowing cockroach Geoscapheus dilatatus reveal two main phenotypes characterized by the presence or absence of alkenes. Both hydrocarbon phenotypes have a large array of components; and populations from different locations, particularly those of the alkene-containing phenotype, are rather variable in hydrocarbon composition. The hydrocarbon phenotypes correlate with morphological differences, viz. the presence (alkene containing phenotype) or absence of tubercles on the anterior edge of the pronotum and the smaller size of the former. The tuberculate form also generally tends to occur further south, though the two types are known to be sympatric at one location in southern Queensland. This correlation of qualitatively different hydrocarbon compositions with morphological differences and largely separate geographical ranges could well suggest that they are different species; and since tubercles occur only in males, cuticular hydrocarbons provide a means for these putative species to be recognized when only females are present in a sample. Three populations appear to be atypical and do not fit readily into either phenotype. (C) 1997 Elsevier Science Inc.