If six-legged invertebrates ever plague your dreams, you’re not alone. Ash trees have nightmares about the emerald ash borer – an invasive species of Asian beetle that is currently destroying ash populations across two dozen US states. One way to start fighting back might be to trick the males into having sex with electrified, nano-scale accurate molds of the females.
Reporting in a new study appearing in the Proceedings of the National Academy of Sciences this week, Michael J. Domingue and his team have tested the first fully synthetic, visual insect lure. It works, for the most part.
The researchers tested the idea that an accurate re-creation of the visual cues that male emerald ash borers pick-up on would snare the males in an evolutionary trap. When human activity kills an organism, makes it less likely to mate, or even just “wastes its time,” that’s an evolutionary trap — organisms can’t help but fall into it. Think of how many birds meet their end at a plate glass window, conditioned by millions of years of evolution to expect unrestricted airspace.
Evolutionarily traps are everywhere, but they are usually accidental. As Carl Zimmer explains at The Loom, this can range from a frog snacking on a Christmas light, mistaking it for a bug, or a beetle trying to copulate with a beer bottle, mistaking it for a mate.
What Domingue and his team have done is intentionally produce one of these evolutionary traps to get the male emerald ash borers where they want them. Once they were there, 4,000 volts did the rest.
Above is a depiction of the study’s design. The researchers attempted to lure the male emerald ash borer beetles with a few different decoys. To do so they pinned four female beetle decoys in the forests of Hungary. One was a intricate mold of a female, one was a 3D-printed model, and two dead females of different species acted as a control. It turned out that the males were lured to the molded and the dead females, but the 3D-printed version was unsuccessful (they landed but didn’t finish mating). Domingue reasons that the males are acutely aware of how light bounces off female carapaces, and therefore the accurate molds with the nano-scale bumps and contours fared better.
But to improve on traditional pheromone-based lures we currently use, the researchers went a step further. They also created a set-up where male beetles interested in a molded female got hit with 4,000 volts of electricity after landing. Not only does this kill the beetle (a good thing), it makes counting beetle populations and tracking them much easier. You can see a video of the collection process here.
As Domingue explained at The Verge, the current techniques for dealing with the emerald ash borer don’t really stack up. Right now we use hundreds of different chemicals and pheromones to lures insects to their doom. But those setups require a lot of maintenance. Then again, more research is needed to make sure the team’s successful evolutionary trap isn’t an indiscriminate killer. It seems to attract not just the beetles in question but also a number of other jewel beetle species, and some females.
Going forward, the main problem the team will tackle is specificity. How can they make decoys that only attract males of the right species? How would you protect the predators of these beetles from getting shocked themselves? Will other decoys work better, or put a real dent in pest populations?
Still, Domingue’s evolutionary trap set for the emerald ash borer is very promising. It makes specimen collection easier and it automatically kills an incredible nuisance to our forests, which the beetle has been since first detection in 2002. The research also sheds light (literally, the team checked with lasers) on how male emerald ash borers find potential mates. The next iteration of these decoys might be even more electrifying to the beetles, literally and figuratively.
Kyle Hill is the Chief Science Officer of the Nerdist enterprise. Follow the continued geekery on Twitter @Sci_Phile.