A beetle that can trick bees into carrying itself into their nests where it can then, live depending on their pollen, nectar and eggs, it adapts its deceptions to local hosts, reports a research by Leslie Saul-Gershenz, a graduate student in entomology at UC Davis.
Aggregations of the larvae of Meloe franciscanus beetles tempt male digger bees (genus Habropoda) by releasing chemical signals that mimic the female sex pheromones. The larvae, which are also known as triungulins, tend to attach themselves to males, transfer to female bees during copulation and this way get themselves a ride back to the nest, where they then feed on bee eggs and provisions and then come out as adult beetles the following winter.
The beetles act as parasites on related- but geographically separate species of bees known as Habropoda pallida from California’s Mojave Desert and H. miserabilis from the coastal dunes of Oregon. Saul-Gershenz was curious know more about how the beetles adapt to their hosts.
“Male bees of both species were more attracted to local parasite larvae than larvae from the distant locale because the larvae tailored their pheromone-mimicking blends to the pheromones of their local hosts,” Saul-Gershenz said. “Additionally, the larval aggregation adapted their perching height at each location to the patrolling height of local male bees.”
Insects especially rely on chemical signals – particularly on their sense of smell – to locate the mates of their own species. There are numerous examples of predators and parasites tapping into, mimicking or ‘exploiting’ these signals. At the same time, as these signals evolve, they aide in the establishment of reproductive isolation of closely related species from each other. In the case studied by the research team the parasites’ chemical signals are diverging along with their host species.
“The larvae cooperate with their siblings for a brief period; they mimic the pheromone of their hosts; they are locally adapted to different hosts both chemically and behaviorally; and their emergence times are plastic across their geographic range. It has been fantastic to unravel this species’ puzzle,” added Leslie.
The study was published recently in the journal Proceedings of the National Academy of Sciences.