One of the key features of insect societies is the division of labor in reproduction between one or a few fertile individuals and many sterile nestmates that function as helpers. The behavioral and physiological mechanisms regulating reproduction in ant societies are still not very well understood, especially in species in which all colony members are reproductively totipotent. In the ponerine ant Harpegnathos saltator, queen-worker dimorphism is very limited, and a few mated workers reproduce (''gamergates'') once the founding queen becomes senescent. Worker oviposition is regulated by highly directed aggressive interactions among nestmates, who can recognize different levels of ovarian activity. We show that variations in cuticular hydrocarbons (CHC) correlate with oogenesis, both for queens and workers. 13,23-Dimethylheptatriacontane is present in egg-layers, but not in infertile workers and queens. Proportions of other CHCs vary as well, resulting in clear separation of the ants in a multivariate analysis. Egg-layers are characterized by an elongation of the chain length of CHCs. We used solid-phase microextraction to measure CHCs in live ants that were experimentally induced to start producing eggs. Over a period of 118 days, CHC profiles of infertile workers changed completely to that of reproductives. The effect of age can be excluded in this modification. This striking correlation of ovarian activity with CHC variation and its correspondence with the observed recognition behavior exhibited by the workers toward egg-laying nestmates suggests that CHCs serve as a fertility signal in the ant H. saltator, a reliable basis for regulating reproduction.A striking phenomenon in biology is the evolution of animal societies in which only a minority of individuals transfer their genes to future generations whereas all others give up personal reproduction and help rearing the offspring of relatives. Hamilton's kin selection theory explains why abstaining from reproduction can be evolutionarily stable. As long as the helpers contribute sufficiently to the reproductive success of relatives, they compensate for the loss of their own direct fitness (1). In ant societies, the queens usually produce all of the colony's offspring whereas the workers raise the brood to adulthood. Workers are morphologically divergent and lack a functional sperm reservoir in most species. They have retained functional ovaries and can lay unfertilized eggs that develop into males, but they usually only do this once their queen has died (reviewed in refs. 2 and 3). This worker infertility can result from either self-restraint or mutual control (4), because male production by workers in queenright colonies often has a negative effect on colony productivity.In situations in which the reproductive interests of queens and workers converge, worker oviposition can be regulated with a simple exchange of information. Many investigations have shown that queens affect the fertility of workers by pheromones (reviews in, e.g., refs. 5 and 6). Indeed, dire...

The electrochemistry of microdroplets, shown to be nearly monodisperse, of N,N,N‘,N‘-tetraalkyl-para-phenylenediamine oils (TRPD, R = n-butyl, n-hexyl, n-heptyl, and n-nonyl) immobilized on a basal plane pyrolytic graphite electrode and immersed into aqueous electrolyte solution is studied using cyclic voltammetry. Upon oxidation of the TRPD droplet to the cation radical TRPD+•, anion uptake from, or cation loss into the aqueous solution takes place, so as to maintain electroneutrality within the oily deposit. The former process is shown to produce an ionic liquid, with the anion insertion taking place at the triple phase boundary of electrode |TRPD oil| aqueous electrolyte; the latter process, in contrast, takes place at the interface between the two immiscible liquids, and with two-thirds-order kinetics. The possibility of a chemical reaction taking place between the electrogenerated and inserted ions at the three-phase junction, viz. redox-catalysis or otherwise, is illustrated via reference to two systems (azide and iodide).