Aggregation and discrimination between strains in Blattella germanica (L.)(Dictyoptera : Blattellidae)

Factors contributing to the formation and maintenance of the stability and cohesion of Blattella germanica (L.) aggregates were investigated. Behaviou ral tests confirmed the role of attractive substances deposited by body con tact in the formation of aggregates. These attractive substances are consid ered to be an aggregation pheromone. Choice tests comparing the attractiven ess of odours between strains from well-separated geographical locations re vealed that cockroaches are able to discriminate and recognize the odour of members of their own strain and avoid odours of unknown strains. Dichlorom ethane and pentane were the most efficient organic solvents for extracting the attractive substances deposited on the body of cockroach larvae. These extracts were as attractive as the substances deposited by body contact. Ex tracts of larval bodies, obtained with these solvents, showed that the attr active substances were not concentrated on a particular part of the body. C hemical analyses (gas chromatography and gas chromatography - mass spectrom etry) showed that the attractive substance contained only cuticular hydroca rbons that play the role of an aggregation pheromone.