A type of parasitic mite, considered the greatest threat to honeybees around the world, is invading hives using the simple strategy of smelling exactly like a bee, researchers say.
Varroa mites, originally detected on Asian honeybee species, have become an invasive pest in many parts of the world. They have now been found infesting and killing the widespread European honeybee, according to a study led by Michigan State University.
They've accomplished this by emitting a chemical stink that mimics that of their honeybee hosts, reducing the chances of being detected and killed, the researchers report in the journal Biology Letters.
"Honeybees rely a lot on chemical communications," a fact the mites have taken advantage of, says MSU entomologist Zachary Huang, the study's lead author.
While chemical camouflage in the insect world isn't that uncommon, it takes a spot-on mimicking of odor to fool honeybees, one of the most socially-sophisticated insect species, the researchers say.
The complicated society of a beehive comprises thousands of individual bees working in a sophisticated caste system, and the mites can't simply trick a solitary bee collecting pollen from a flower but must fool an entire society, they explain.
The mites accomplish this not only by smelling like bees but also by successfully creating the specific collective scents of small, individual colonies, Huang says.
"They are essentially getting through the door and reaching the inner sanctum by using bees' own complex communication codes against them," he says.
The chemical codes bees use are based on hydrocarbons, the most basic organic compounds, and the mites can manipulate their production of similar chemical odor compounds to fool bees in a hive, creating a smell that invokes acceptance, the researchers report.
Mites have even displayed the ability to change the chemicals they produce on their skin to mimic an entirely different species of honeybee, they say.
They can accomplish this change in a very short time, adapting their chemical camouflage in days rather than having to evolve over several generations, Huang notes.
"The mites from Asian honeybees, or the original host, are more efficient in mimicking both Asian and European honeybees," he says. "This remarkable adaptability may explain their relatively recent host shift from Asian to European honeybees."
The bees are not without some tricks of their own, displaying an ability to also adapt to detect the invading mites, the scientists point out.
"Our results give a clear illustration of an arms race between the parasites and the host bees based on chemical mimicry and its detection," Huang says.
