Silent and Deadly: Fatal Farts Immobilize Prey

The adult form of a silent and deadly predator: a Beaded Lacewing. This species is from Udzungwa, Tanzania. Patrick Coin/CotinisClick to Open Overlay Gallery

The beautiful animal in the photo above is a Beaded Lacewing. While the adults are delicate and lovely, they begin life as ferocious tiny predators lurking in the nests of termites. These larvae live unmolested in their nest, silently striking down termites from behind—and for one species, with their behind.
When a baby Lomamyia latipennis gets hungry, it stuns a termite with a “vapor-phase toxicant” released from its anus. That’s a fancy way of saying it farts on it. In fact, their farts are powerful enough to immobilize six termites with one blow.
This is how you wield a Death Fart, if you are a small predatory neuropteran:

“A larva repeatedly approached and retreated until the tip of its abdomen was directed at the termite’s head. The apex of the abdomen was lifted and waved past the termite’s face, without contact. The termite… was not repelled, as it made no obvious effort to escape. One to three minutes later it was incapacitated, lying supine, with its legs moving irregularly.”

Once the larva delivers its toxic toot, it can leisurely scuttle over and chow down. If a few extra termites are caught in the backdraft, that’s just extra food.
In laboratory tests, experimenters determined the fecal fume-induced paralysis lasted for three hours, and if not eaten, the termites eventually died. Even more astonishing is that early stage L. latipennis are tiny, about 0.07 mg in size. The average size of their termite prey was 2.5mg. That is some seriously potent flatulence.
The experimenters coaxed the larvae into farting on other insects commonly found in termite nests—fruit flies, two kinds of small wasp, and book lice—but they were unaffected. The spectacular sphincter specificity of the species seemed only affected by size; very large termites (>5mg) were slightly stunned.

How Do You Weaponize a Fart?

Beaded lacewings have been described as “unaccountably neglected… Generally speaking, very little is known about Berothidae at present.” There aren’t any good photos of this species, other than some older black and white blurry photos.
Unfortunately, just what chemicals create air biscuit asphyxiation were never identified by the researchers in the original study. There is a fairly deep literature on insect farting; a survey of more then 110 species found many of them were significant methane producers, especially roaches and termites.
That’s mostly a consequence of a high-fiber diet and a lot of gut bacterial symbionts. But it’s unlikely that beaded lacewings are ripping enough methane to knock out a termite—it must be something else unique to the species.
And their gassy butts aren’t the only thing strange about L. latipennis. The first and third instar larvae are highly mobile and carnivorous. But in between, there is a strange stage that doesn’t move and is non-feeding. Why? We have no idea.
Indeed, this whole group of insects (Neuroptera) has something just not right going on with their colons. A constriction between their stomach and hind-gut prevents immature stages from pooping. They work around this problem by acting more like spiders than insects. Their pointy, straw-like mouthparts inject digestive enzymes into the bodies of their victims.
Once the innards of their prey are liquified, they slurp it up. Any solid matter that happens to be ingested is retained until they turn into their adult form and can finally take a giant dump.

Tooting Their Own Horn—Or a Bum Rap?

To date, no one has been able to repeat the original experiments, so it’s possible that this is just a vapor trail. We don’t know what makes a death fart; maybe nothing. All insects have weird and wonderful chemical secretions; perhaps the original experimenters missed something. In the words of neuropteran expert Professor John Oswald: “the gaseous allomone story in larval berothids still requires further investigation and confirmation.”
Several kinds of lacewing relatives have anal attack plans. The species Chrysoperla comanche exudes a droplet from its anal glands and waves it around threateningly if disturbed. They are master contortionists, raising their abdomen over their heads to anoint the head of an annoying ant. It seems to act like chewing gum; it’s incredibly sticky and ants work frantically to clean it off. (I’m not sure why the experimenters thought to test this, but the larva can still perform this yoga move after decapitation. It’s a reflex to being prodded in the side.)
Unfortunately, no one has identified the chemical component for this species either, but whatever the stuff is, they have a lot of it up their butt. In lab tests, larvae were able to defend themselves from an average of eight ants before they began to run out. It’s the same adhesive that they use to cement themselves to a leaf when they change from a larva into a pupa. In this case, the insects found a new use for a previously existing substance.
Adults of the common green lacewing produces a compound called skatole, which smells just as bad as the name sounds. In Sweden, adults have the nickname Stinkslända [stink-fly].
Maybe all around us farts are causing death and destruction on a tiny, tiny scale. We just don’t know.

Specifically, Sphincters

I’ve focused on the scatological part of this story, because seriously, we all have that one officemate that seems to exist on falafel and bean burritos. But beyond that, it’s a fascinating example of just how little we know about the natural world around us.
This investigation into insect farting came about because some biologists were curious. Not because they thought they would find an important compound to control termites; but because they thought this was a nifty little animal and wanted to learn more.

The cover of Astounding Stories, June 1932, clearly foreshadowing the Ass-Yodel method of termite control. Astounding Stories, H. W. Wessolowski, artist.Click to Open Overlay Gallery

Insects make up nearly 80 percent of described animal species so far, but an estimated 60 percent of insect species are undescribed. We don’t know much about them other than a few specimens.
Entomology is fairly friendly to interested amateurs; the natural history of many of our insects were worked out by people who were observant and kept careful records. Perhaps someone will be inspired to start recording and collecting these little predators.  An enormous unknown world awaits you at your feet.
And if you ever happen to be attacked by giant termites like these fellows, now you have a new weapon to try.

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J. Johnson & K. Hagen. 1981. A neuropterous larva uses an allomone to attack termites. Nature 289, 506 – 507 1981); doi:10.1038/289506a0