Mechanism underlying cuticular hydrocarbon homogeneity in the antCamponotus vagus (SCOP.) (Hymenoptera: Formicidae): Role of postpharyngeal glands.

The aim of the present study was to investigate the regulation and the homogeneity of the chemical signature between members ofCamponotus vagus after experimentally changing the cuticular chemical signature by topically applying hydrocarbons. Topical application of pentane (solvent) to the cuticle of isolated workers led to a significant decrease in the quantities of the cuticular hydrocarbons measured within 3 hr, followed by an increase within the following 3 hr and a period of relative stability from 9 hr to 14 days. On the other hand, after topical application to isolated workers ofn-tetracosane, a hydrocarbon existing only in trace quantity in this species, the quantity of this hydrocarbon measured over time in the epicuticular wax tended to level out at about 14 days after treatment. In contrast, topically applied (Z)-9-tricosene, an unsaturated hydrocarbon not normally synthesized by this species, decreased dramatically within a few hours and had completely disappeared within 14 days. (Z)-9-Tricosene applied to one member of a group was present in the postpharyngeal glands of the other members from 30 min to seven days of cohabitation. The highest levels were recorded in all six workers in each group after one day. GC-MS analyses showed that (Z)-9-tricosene was present in the cuticles of some untreated workers only after four and seven days of cohabitation with a treated worker. These data suggest: (1) that the deposited (Z)-9-tricosene decreased very quickly on the cuticle of the treated worker, although the total amount was spread over the cuticle and postpharyngeal gland and (2) that it was absorbed by the nontreated workers via the postpharyngeal glands during licking or grooming activities and reincorporated into the cuticle at four and seven days. When the treated worker was separated from the other ants by a wire mesh, (Z)-9-tricosene was detected neither in the cuticle nor in the postpharyngeal gland of nontreated workers.