Fueled by a late-summer heat wave, several large wildfires have been burning across the Western US, forcing thousands of people to flee their homes and turning the sky in parts of Southern California an eerie orange.
This is of course bad for pretty much everyone. Except for Melanophila beetles.
These insects, which are roughly the size of pumpkin seeds, are pyrophilous — meaning, they love fire. They actually depend on it for their reproduction. When most animals are fleeing from wildfires, these insects fly toward the flames, copulate among the embers, and lay eggs.
Those eggs then hatch into wormlike larvae that feast on the recently burned wood.
A fiery orgy may sound like an awful idea, but for these bugs it comes with a number of advantages. When forests are shrouded in flames, there aren’t many insect-eating predators around, which is one reason this behavior may have evolved, scientists say.
As our cars and power plants continue heating up the planet, the wildfire season will only get longer and more severe. Animal adaptations like this offer some useful perspective: They remind us that climate change won’t just be a dead end for all creatures. Some species are hot for heat.
How fire beetles find flames
Although these beetles don’t look all that remarkable, they have an impressive anatomy. Like home security systems and night-vision goggles, their bodies contain infrared sensors. These sensors — known as sensory pit organs — detect infrared radiation, which is a proxy for heat. Located on the insects’ underside, those pits point them in the direction of a fire.
Using sensors in their antennae, these beetles may also be able to detect smoke. During football games at the University of California Berkeley in the 1940s, a haze of tobacco smoke from fans lighting up would regularly attract a swarm of Melanophila beetles that would anger fans, according to author Jame Agee in his book Fire Ecology of Pacific Northwest Forests. Since cigarettes don’t emit much heat, researchers suspect it was the smoke that may have drawn them in.
Using these sensory systems, fire beetles can detect flames from enormous distances. One study in 2012, based on modeling, suggests that these fire bugs can become “aware” of large fires from roughly 80 miles away, or about the distance between New York City and Philadelphia. So often where you find fire, you find fire beetles.
Firefighters know this fact all too well.
“Wildland firefighters hate these beetles,” Lynn Kimsey, an entomologist at the University of California Davis and director of the Bohart Museum of Entomology, told me last year. “When you’re in working on a fire line, especially around trees that are burning, the beetles will come in, in big numbers, and they’ll get into your turnouts and bite.”
The bites feel a bit like a bee sting, and sometimes firefighters wear bee veils to protect themselves.
Why these beetles seek out scorched Earth
When male beetles arrive at a forest fire, they have one thing on their minds: sex. The insects often perch on a tree “close to burning or glowing wood or hot ashes,” researchers have explained, and when they find a female, “they try to copulate vigorously” (in the literal heat of the moment). The females then lay their eggs under the bark of burnt trees.
Why choose freshly burned forests?
The simplest explanation is that their offspring, the beetle larvae, can only persist on the wood of burned trees. When a tree has been scorched by flame, it has a weak or nonexistent defense system, allowing the beetles to easily bore through wood under the bark. “The beetles can get in there and feed freely,” Kimsey said.
What’s more is that most insects tend to avoid recently burned areas, so when the baby fire beetles emerge, they have less competition for food — they get a wood buffet all to themselves. These areas also typically have fewer insect predators, such as birds. (Although, in a remarkable example of evolution, some species, like the black-backed woodpecker, have evolved to eat fire-associated insect larvae.)
Yet another possible reason for why they chase fires is that beetle larvae may develop faster in freshly burned areas. Heat speeds up growth, like a cozy incubator, some evidence suggests. That means beetles can produce more babies in less time.
A rare climate change winner?
Rising temperatures linked to climate change are already a problem for many ecosystems and species. Warming fuels coral-killing heat waves and hurricanes, causes some animals to shrink and others to get insomnia, and generally makes much of the planet less suitable for life.
At least in the short term, fire beetles (and some beetle pests) may be able to defy these negative trends. Climate change is making wildfires more widespread and extreme, and scientists suspect the beetles can only breed with fire.
For now, this is just speculation, Kimsey said. “We have no idea what they’re doing when there isn’t a fire,” she said.
What’s clear is that climate change will produce not only losers but some winners. This beetle species may be one of them. A world on fire could be a world full of horny beetles.