What has six legs and two pairs of balls? No, it’s not the start of a lewd joke. It’s the Brazilian treehopper, a pea-sized, rainforest-dwelling insect that sports a headdress worthy of a royal wedding.
The purpose of these bizarre, helicopter-like orbs – actually an elaborate ‘pronotum’ (an insect body segment just behind the head) – is still something of a mystery. Could they be an evolved structure like a peacock’s tail, used by males to show off their genetic vigour to others? Unlikely: both males and females are endowed with balls, so to speak.
Could they have evolved to look like a second ‘dummy’ head which predators mistakenly aim for when attacking? A lack of observations of this happening in the wild suggests not.
Instead, insect scientists suspect that the structures evolved to mimic the handiwork of a parasitic fungus called Ophiocordyceps unilateralis, which invades the bodies of ants and then bursts Alien-style out of them, creating similar structures sprouting from the deceased insect.
So the Brazilian treehopper is left alone because, well, no predator wants to risk accidentally eating the same fungus.
Though unusual among other insects, these ornate structures are a common feature among the 3,200 species of treehoppers, and can sometimes resemble thorns, leaves and even bird droppings.