When war breaks out on the dung heap, these insects mimic the opposite sex to avoid big bullies
Nick Baker’s HIDDEN WORLD The popular naturalist, author and TV presenter reveals a secret realm of overlooked wildlife
LEISTOTROPHUS VERSICOLOR
Rove beetles don’t look like a typical beetle. They don’t share the profile of a ladybird or dung beetle, nor do they have domed wing-cases or cutesy features. They are fast and mean-looking predators, and when they are not scavenging, their elongated bodies allow them to slip into the tightest spaces in pursuit of their prey.
One in particular stands out from the crowd. In the tropical forests of the Americas lives an intriguing species called Leistotrophus versicolor. It is on the chunky side for a rove beetle; a strange, lumpy, hairy and mottled insect. Alert and forever twitching, it is armed with large bulbous eyes and a formidable pair of mandibles that allude both to its hypervigilance and brutish nature.
Like many rove beetles, it is attracted to mammal dung because these short-lived, steamy odiferous deposits offer dinner in the form of flies, as well as the promise of potential partners.
It is here, on the pile of poo, that things start to get interesting. Leistotrophus versicolor exhibits a marked sexual dimorphism, with the males generally much bigger than the females and armed with larger mandibles. The males themselves also vary in size, with the bigger individuals bullying and barging their way to dominate the food, trumping their smaller rivals and excluding them from the pile. In doing so, they command the right to mate with the more delicate females, a tactic scientists refer to as resource-based polygyny.
You might expect the smaller males to be the losers and that, unable to compete physically, they get shoved aside, their mating game over. But no – it turns out that there is another strategy at play. If it suits, when confronted by a larger male, the smaller male can impersonate a female. By mimicking the female’s pre-copulatory courtship behaviour – raising the abdomen and waving its yellow-orange tip from side to side – he diffuses the aggressive encounter with the larger male. The larger male starts courting, fluttering his antennae over the pseudo-female and even attempting copulation. In many instances, he is led on a merry dance off the dung, before the pseudo-female chooses the appropriate mom
