Nest volatiles as modulators of nestmate recognition in the ant Camponotus fellah.

When ants from alien colonies encounter each other the stereotypic reaction is usually one of aggressive behavior. It has been shown that factors such as queen-derived cues or nest-odors modulate this reaction. Here we examined whether nest volatiles affect nestmate recognition by observing the reaction of nestmates towards individual workers under one of four regimes: completely isolated; isolated but receiving a constant airflow from the mother colony; as previous but with the passage of nest volatiles towards the isolated ants blocked by adsorption on a SuperQ column; or reversed airflow direction-from the isolated ants to the nest interior. Ants that had been completely isolated for three weeks were subjected to aggressive behavior, but not those that had continued to receive airflow from the mother colony. Adsorbing the nest volatiles from the airflow by SuperQ abolished this difference, with these ants now also being subjected to aggression, indicating that nest volatiles can modulate nestmate recognition. Reverse airflow also reduced the level of aggression but to a lesser extent than airflow directed from the mother colony. In queenless colonies the overall aggression was reduced under all regimes, and there was no effect of flow, suggesting that the volatiles involved are queen-borne. The SuperQ adsorbed volatiles originated from Dufour's gland secretions of both workers and queen, implicating them in the process. Cuticular hydrocarbon profiles were not affected by exposure to nest volatiles, suggesting that the latter either constitute part of the recognition cues or affect worker behavior via a different, as yet elusive mechanism.

Postmating changes in cuticular chemistry and visual appearance in Ectatomma tuberculatum queens (Formicidae: Ectatomminae).

In the ectatommine ant Ectatomma tuberculatum, the visual appearance of queens changes after mating and ovarian development in that their cuticle turns from shiny to matte. In this study, we have shown that this change seems to be caused by 15-fold accumulation of hydrocarbons, in particular heptacosane that covers the multiple grooves present on the cuticular surface creating a wax coat in mated fully fertile queens. Analyses of the scrapped wax revealed that it is composed largely of heptacosane. Peak-by-peak comparison of the cuticular hydrocarbon (CHC) composition of mated, virgin with developed ovaries and virgin with nondeveloped ovaries revealed significant differences between the queen groups. Although the total amount of the CHC of virgin queens with developed ovaries was not higher than virgin queens that did not have developed ovaries, the composition showed a shift toward the mated queen. While it is possible that the large accumulation of hydrocarbons may give extra physical and chemical protection to queens, we propose that the switch in the relative abundance of heptacosane and nonacosane and perhaps of other components is indicative of being a mating and fertility cue. This is the first report in social insects where external chemical changes are accompanied by changes in visual appearance.