Queen honeybees not only mate with lots of males, but they also brag about it to the whole hive.
A chemical signal from queen bee glands lets the female worker bees know that her mating dalliances were successful, and hint at just how fruitful they were, according to a study published Wednesday in the online journal PLOS One.
The honeybee, Apis mellifera, is equipped with one of the most complex chemical signaling systems in nature, with multiple pheromones controlling the social organization of the hive. They can encourage foraging, attract mates, keep new queens from being reared, and even change the population composition of the hive and alter the gene expression of worker bees.
But entomologists have wondered what kind of information those chemicals conveyed: Were they relatively simple messages, or did they go into detail? Did the chemical composition change depending on the physiological state of the queen?
Answers could help shed light on why workers seem to be replacing queens more rapidly amid a wholesale collapse of domestic bee colony populations.
A team of entomologists from Penn State, North Carolina State and Tel Aviv universities examined chemical changes of pheromones from isolated aspects of the mating process, and from various mating outcomes, then tested how worker bees reacted to these chemicals.
Results suggest that the composition of these pheromones changed, depending on the queen bee's physiological state, but so did worker bee response. Workers exhibited the strongest attraction to the pheromones from highly inseminated queens, compared with those injected with less semen or with plain saline or with those that were virgins.
"It looks like the queen is not only saying, 'OK, I'm here,' but she's also telling the workers that she's a mated queen, and that she's either poorly or well mated -- which is pretty important, because she uses the pheromones to regulate the social organization of the hive," said Penn State University entomologist Elina L. Niño, lead author of the study.
The queen mandibular pheromone induces female workers to form a retinue around the queen, a group contact that helps spread the chemicals throughout the colony. Among other effects, the pheromone increases foraging and inhibits rearing of new queens and the activation of worker bee ovaries. All of those can contribute to a longer-ruling queen and more productive colony.
Niño said the results reinforce the importance of trying to keep the queen and drones healthy, to avoid the hive productivity loss that comes with interruption of a queen's tenure.
"It's important to have a supply of healthy and mature drones during the mating process, and, of course, we have to have healthy queens, because we are not sure what is causing these poor matings and this quick queen loss and queen replacement," Niño said. "So it's really important to help promote the health of those queens and drones."