Chemical signaling among social insects, such as bees, ants and wasps, is more complex than previously thought, according to researchers at Penn State and Tel Aviv University, whose results refute the idea that a single group of chemicals controls reproduction across numerous species. "While the hypothesis that many social insect lineages all use the same chemical signals -- known as pheromones -- was fascinating, we were skeptical that such complex behaviors could be regulated by a simple, common mechanism across such very different species," said Etya Amsalem, postdoctoral fellow in entomology, Penn State. "It seems more likely that pheromones evolved uniquely in different species, as these species experienced different environments and different social pressures."

The results appear in today's (Oct 21) issue of the Proceedings of the Royal Society B.

According to Amsalem, in January 2014, a study was published suggesting that the chemical signals produced by queens from a variety of species, including bumblebees, ants and wasps, are very similar. The paper posited that this common group of chemicals is responsible for inhibiting reproduction in workers across these different species.

"One of the most fascinating behaviors in social insects is that most of the females in a colony (the workers) do not lay their own eggs, and instead help rear the eggs produced by their mother (the queen)," said Amsalem. "In some species, it is known that the queen produces pheromones, to inhibit the workers from reproducing."

The previous study examined the ovaries of worker bumblebees in the presence of putative queen pheromones to see if they were active -- producing eggs -- inactive, or regressed. Regressed ovaries are those in which the developing eggs have absorbed back into the tissue.

The researchers found that exposure to a putative queen pheromone, c25, caused increased levels of ovary regression, but had no other effects," said Amsalem.