Nature is full of horrors, including zombie wasps and parasites that sound too cruel to be real. One of the most vicious and twisted is the blister beetle.
The beetle lures in male bees with the promise of sex, only to eat the bees’ offspring—and anything else they can find. New research highlights just how these beetles’ parasitic behaviour developed and how they pull in their unsuspecting prey.
A blister beetle’s life cycle is like that of most other beetles—for the most part. Adult beetles lay many eggs that hatch into larvae, which grow into adult beetles, which lay more eggs. But at the larva stage, blister beetles take a slight detour that brings them in contact with a particular species of bees.
When the beetle larvae hatch, they group together and begin emitting a specific pheromone. This pheromone is almost exactly the same as one produced by female bees looking to mate, and that scent is enough to lure in innocent males. When those males fly down to investigate, the beetle larvae hitch a ride on their backs.
Later, that male bee will find a real female with whom to mate. When that happens, the beetles transfer to the female. When the female lays its eggs, the beetle larvae crawl off and devour them. They also eat the food that the bees left to nourish their eggs, the nest surrounding them, and the bees themselves if they’re not careful.
To pull off such a deceit, the beetle larvae need to coordinate to produce enough pheromones to lure in a bee. They also need to sit at the right height to catch that bee as it’s passing by. Too high or too low and the bee will fly on, oblivious.
Interestingly, the new research finds that the details of this charade can change by region. For example, the researchers looked at populations of bees and beetles in the Mojave desert and coastal Oregon and discovered that these different regions contained differences in their beetle populations. These regions have different species of bee to prey on, so these beetles have developed different pheromones to cater to their different host populations.
These differences are so ingrained that beetles moved from the Mojave to Oregon—or vice versa—can’t attract the local bees. The beetles are so well adapted to the bees they target that they simply can’t survive on any other kind. That’s bad news for these parasitic beetles, though, given the declining bee populations around the world. If this trend continues, these beetles might find themselves looking for a new meal soon.
Originally published on Popular Mechanics