C is for creepy, that's good enough for me. Patrick Landmann / Science Source
C is for creepy, that's good enough for me.
Campylenchia latipes, so named because I haven't the slightest clue. USGS Bee Inventory and Monitoring Lab/Flickr
Campylenchia latipes, so named because I haven't the slightest clue.
The buffalo treehopper looks more like the aliens from Independence Day than a buffalo. USGS Bee Inventory and Monitoring Lab/Flickr
Let’s just admit it: We all have body issues to some degree. I, for instance, was informed a few years back by a drunk lady in a bar that I am in fact slightly bow-legged, which was the first I’d heard of it. The revelation was enormous, and still remains a source of some anxiety for me.
More absurd creatures:
But our image issues are mere trifles compared to what must be going through the minds of the treehoppers. These are without a doubt nature’s most bizarre insects, having evolved into a huge range of shapes: some with jutting, curling heads, others that look like they have ants on their backs, and still others that do a spot-on impression of a fungus that invades other insects and erupts from their bodies.
What you’re seeing is a highly modified pronotum, the segment just behind an insect’s head. But the problem, at least for the time being, is scientists would have a hard time telling you definitively what purpose they serve. “That’s actually a really big question that we haven’t solved,” said entomologist Matthew Wallace of East Stroudsburg University in Pennsylvania. “It’s kind of interesting, because it’s what they’re known for. Some are just so strangely shaped that you look at it and say, ‘How could they survive like that?’”
But no creature evolves to suck at survival. Quite the opposite. Those best adapted to their environment pass down their genes for, say, goofy-yet-beneficially-shaped bodies. Scientists like Wallace are trying to piece together exactly how these ridiculous pronota are helping the treehoppers survive. What seems evident, though, is different species of treehoppers probably have adopted different strategies with those weird bodies, from camouflage to mimicry to defense.
That’s no radio antenna. It could well be that this treehopper is mimicking a fungus that invades other insects and erupts out of their bodies. And if that’s not something to strive to be in life, I don’t know what is. © Murray Cooper/Minden Pictures/Corbis
Perhaps the most remarkably complex among them are the species of the tropical genus Bocydium, shown above. That pronotum will look miiiiighty familiar to those acquainted with the Ophiocordyceps fungus, which invites itself into ants’ brains and mind-controls them, instructing them to bite down on a leaf. The fungus then kills its host and erupts from the back of the ant as a stalk and globes, which rain spores on the poor thing’s comrades below.
This treehopper, some scientists think, could have evolved to mimic that fungal structure erupting from ants, as well as other bugs they attack, “so it wouldn’t be palatable to predators” that know to avoid diseased insects, said Wallace. Even if the predator doesn’t buy it and goes for a nibble, the towering structure can break off in its mouth, leaving the treehopper unharmed and decidedly less top-heavy. The predator gets nothing but a non-nutritious chunk of exoskeleton.
Other species of treehopper look like ants sans fungi—insects that are more than capable of defending themselves with stings and nasty mandibles, which the treehoppers lack. They could therefore be mimicking the ants to exploit their reputation as scrappy fighters. “And then some of those species in that same genus, they have the coloration of a wasp,” said Wallace. “And so they kind of combine that warning coloration with the ant structures.”
This one is probably imitating an ant. That may not seem like it’s choosing a very ferocious animal to mimic and to therefore scare potential predators away, but you do not want to mess with ants. I messed with ants once. It’s probably why I’m bow-legged. © Murray Cooper/Minden Pictures/Corbis
Treehoppers aren’t just ripping off the ants’ style, though. They’re employing the creatures. Sap-feeding insects like treehoppers and the related aphids produce a sugary excrement called honeydew, which you’ll now think about whenever you eat honeydew, and which ants are crazy for. In exchange for tolerating the ants drinking the honeydew from their bums, the treehoppers get a security detail. The ants are, in essence, running a protection racket.
“It’s funny, if you try to collect some of these treehoppers the ants will be very aggressive toward you, they’ll try to bite,” said Wallace. “And so it’s just amazing to think about all of these relationships and how dependent the ants are on the treehoppers, and the treehoppers on the ants.” Word of the bounty gets around, though: Bees, wasps, and even geckos will seek out treehoppers for their honeydew, which provides valuable carbohydrates.
But back to the pronota. Still other treehoppers choose to use theirs to blend in with their surroundings, mimicking leaves or twigs or buds. And those that mimic thorns have the added bonus of being essentially a living spike, which doesn’t go down a predator’s throat so easy. Such species can pull off this disguise because treehoppers are largely sedentary, drilling into tree branches with what are appropriately known as “piercing-sucking” mouthparts and slurping out the sap—and just kinda hanging out there all motionless and peaceful-like. That is not to say, though, that treehoppers are lazy. If threatened, they can pull off some pretty decent flight. Decent, that is, considering the outrageous structures they’re schlepping around.
What doesn’t seem to be a factor in the evolution of the pronotum is what is known as sexual selection. This is when males use flamboyant features or dances or calls to win the affection of females (though there are very rare exceptions where the dynamic is switched, such as a species of cave insect whose females have the penises and compete for males, who give them not only sperm but highly coveted and nutritious “nuptial gifts”). Typically when sexual selection is at work, you’ll see a good amount of sexual dimorphism—very obvious physical differences between males and females. But for all of the flamboyance of treehoppers, there isn’t much variation between the sexes, so Wallace doesn’t think that sexual selection is at play here.
Beyond the camouflage and mimicry and defensive benefits, there’s evidence to suggest the treehopper pronotum is in fact a sensory structure as well. “If you look at them underneath the ‘scope they’re loaded with hairs and pits and things,” said Wallace, “and that would seem to hint toward some type of reception, whether it’s chemicals or sounds.” One paper has suggested that the enormous structures could even be dispensing pheromones to bring boys and girls together for sexy time.
Treehoppers have another method of rather unconventional communication, at least to us humans. To warn their branch-mates of danger or to clue them into food, they send out vibrations, which other treehoppers pick up with their legs. And even though treehoppers are related to the patently obnoxious cicadas, we can’t hear the vibrations of the treehoppers.
Well, not without help, at least. Lucky for us, an enterprising scientist named Rex Cocroft spends his days strapping microphones to branches to listen in on treehopper conversations. While cicada calls make you want to pull your ears off and burn down forests, amplified treehopper calls are positively enchanting—and at times creepy. Listen to examples here, here, and here, and check out an archive of more here.
In addition to adults using these sounds to communicate between each other, a mother will stand guard over her young and chatter with them in the same way. And that’s a bit weird for an insect: Most species ditch their eggs after they’ve laid them, save for the truly social insects like ants and termites and bees, which work together in colonies toward a common goal. (Interestingly, there’s just a single oceanic critter that forms these societies: the pistol shrimp, which sets up monarchal kingdoms inside sea sponges.) Treehoppers are what are known as subsocial insects, meaning they’re not forming societies as such. Instead, ma just sticks around to see that her weird kids grow up to blow the minds of humans like us, which is nice of her.
For all we’ve learned about the treehoppers, mysteries still abound. But thanks to the work of scientists like Wallace and Cocroft, who traipse through forests braving angry ants to gather treehoppers and strap microphones to trees, we’re getting to know these bugs better and better.
Not much the researchers can do about these legs of mine, though.
Browse the full Absurd Creature of the Week archive here. Know of an animal you want me to write about? Are you a scientist studying a bizarre creature? Email matthew_simon@wired.com or ping me on Twitter at @mrMattSimon.
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