Beetle bombardment

To understand what the false bombardier beetle is, you need to understand what makes the true bombardier beetle so special.

The term “bombardier beetle” is used to refer to a group of ground beetles that pack a really hot punch. When threatened or attacked by a carnivorous ant, spider, frog, toad, lizard or some other predator, the bombardier beetle turns away from the threat before blasting pulses of 212-degree noxious chemicals from its rear end. Exposure to the boiling brew causes most predators to retreat, but some are killed in the process. Survivors know full well not to mess with the bombardier beetle.

A member of the genus Galerita, the false bombardier beetle shares its size and appearance to its cousin. It grows between 17 and 25 millimeters long and sort of resembles a fat ant. Like most other insects, it walks around on six orange legs and has long antennae, which it uses to get a sense of its surroundings. Its head and abdomen are black, but its thorax (mid-section) is orange. The false bombardier beetle has everything an ordinary bombardier beetle has except for one thing: the firepower.

Why would this little guy closely resemble a bombardier beetle? If you happened upon a false bombardier beetle in the wild, chances are that you would mistake it for its cousin. And that’s the idea. This is called mimicry, and there are many cases of it in nature.

When I’m outside, I’ll often mistake the yellow-and-black-striped hoverfly for a bee or wasp, insects I definitely want to steer clear from. Predators commonly confuse the viceroy butterfly for its poisonous cousin, the monarch. In the case of the false bombardier beetle, predators instantly mistake its orange and black body for a true bombardier beetle and steer clear.

That being said, the false bombardier isn’t completely harmless. Contained within its abdomen are defense glands that hold a noxious brew of chemicals. While the brew contains acetic acid and lipophilic components, 80% of it is made up of formic acid. Formic acid can cause irritation and corrosion to human skin, eyes and the inside of the nose.

False bombardier beetles eject these chemicals as a spray, aiming for their targets with great accuracy. They can store up to 4.5 milligrams of formic acid at a time, enough for six blasts. If they fully deplete their supply, it takes them about 37 days to completely replace it. It’s little wonder why this beetle relies more on its looks to defend itself.

The false bombardier beetle is common across much of North America, but it is most commonly sighted in moist, wooded areas and backyards. These habitats provide the perfect location for the beetles to deposit their eggs, which are laid on the underside of smooth leaves in a mud cell shaped like a purse. These insects can be active either day or night, and primarily feed on smaller insects.

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