Mimics with murder on their mind.
Nature is full of copycats. Many living “mimics” have evolved to look, sound, act or even smell like other organisms.
The study of mimics goes all the way back to the English explorer and naturalist Henry Walter Bates. In the 19th century, he observed species copying each other and used these examples to help prove Charles Darwin’s theory of natural selection.
Bates was the first to realise that some harmless species evolve to look like dangerous or disgusting-tasting species to avoid being eaten. This is known as defensive mimicry, or Batesian mimicry, and we looked at some of the best examples in Issue 81 of Cosmos.
But what about those critters, often dangerous, that evolve to look like something harmless?
Later in the 19th century, the British evolutionary biologist Sir Edward Bagnall Poulton put forward the idea of “aggressive mimicry” in his book
The Colours of Animals. He defined it as “one animal resembling another in order to approach it without exciting suspicion”.
Suspicion of what? Getting eaten, of course!
There are hordes of brutish beasts out there pretending to be something they’re not just to get an easy dinner. And some of their disguises are really weird. STEPHEN FLEISCHFRESSER presents his Top 6.
1 ORCHID MANTIS
Lots of praying mantises use camouflage to blend into their environment and ambush their dinner, but the Orchid Mantis of Indonesia has taken things a step further.
For many years, scientists thought it was cleverly hiding among orchids, waiting to ambush insects that landed on the flowers to feed.
However, we now know that it isn’t hiding at all. It is actually the only known flower-mimic in the world – and an aggressive one at that. And it doesn’t just pretend to be orchids.
The orchid mantis mimics different flowers; sitting close to the real deal, which are attracting other insects to their doom. When they approach, it catches them with its powerful front legs. Its mimicry is so effective, in fact, that insects are more attracted to it than they are to real flowers.
2 ANT-MIMICKING APHID
This is a split personality insect that can turn on its friends in a second.
Aphids often form mutually beneficial relationships with ants. They feed on plants and produce a sticky sweet substance called honeydew, which ants love to eat. In return, the ants appear to protect and even farm the aphids, so that they can get hold of more honeydew.
The ant-mimicking aphid doesn’t always play the game, however. It comes in two distinct physical forms that are identical genetically – but very different in behaviour.
One is just like a normal aphid; the other exudes chemicals that mimic the secretions of young ant larvae. This tricks approaching ants into thinking a baby ant has escaped the nest.
When an ant picks up what it thinks is a baby ant and takes it into the brood chamber – the supposedly safe place where larvae grow up – the aphid turns into a blood-sucking monster, biting into the larvae and feeding on their internal fluids.
4 IRANIAN SPIDER-TAILED VIPER
The name says it all. This venomous snake from western Iran has a very peculiar hunting method. But it wasn’t until recently that it came to scientific attention.
When a specimen was first taken in 1968, scientists saw its curious tail and decided it was a bizarre one-off abnormality. However, in the early 2000s other researchers realised it was representative of an entire new species, which was formally described in 2006.We now know that this viper’s tail has evolved to look exactly like a spider.
Well camouflaged, the snake hides amongst rocks while wagging said tail, with its distinctive colour and shape, across the stones. This closely mimics a spider running about.
When various insect-eating birds swoop down for a snack, the viper strikes.
Just when you thought nature couldn’t get any stranger or more dangerous, science finds a snake that looks like a spider.
3 BIRD-DROPPING SPIDER
This common Australian spider is also known as the Orchard Spider, because it loves to hang around in fruit trees.
It is both a defensive and an aggressive mimic.
The defensive strategy is pretty simple. Its colours and its habit of sitting still with legs tucked underneath it make it easily mistaken for bird poo. This helps it avoid being eaten by birds – for obvious reasons.
At night, however, it turns into an aggressor, hanging from leaves or twigs on a single thread and releasing pheromones (chemicals that have biologically important scents) that mimic those given off by female moths to attract a mate.
The distracted male moths, lured by what they think is the female moth’s perfume, fly toward the spider. Once they are in range, the predator in its dastardly disguise uses its powerful forelegs to capture them.
Even spiders like a home-delivered dinner.
5 LAMPSILIS MUSSELS
Freshwater mussels of the Lampsilis genus are native to North America, and they are really weird aggressive mimics. Unlike the other examples of aggressive mimicry we’ve looked at, they aren’t predators. They’re parasites!
Their larvae have evolved to mature while stealing nutrients from the gills of large predatory fish such as bass. Once they’ve had their fill, they drop back to the riverbed to take up the regular life of a mussel. In most cases the fish is perfectly fine afterwards.
The problem? How does a mussel that is stuck to the bottom of a river get its larvae onto the gills of a fast-moving fish?
Lampsilis has an ingenious solution. It has evolved in such a way that its mantle – the flesh around the edges of the shell – looks remarkably like a small fish called a minnow. It even moves this lure in a way that almost perfectly mimics the way minnows move.
Eventually a larger fish will come in for a feed of minnow. As it attacks, it injures its gills on the shell, which prompts the mussel to release a milky cloud of its larvae. The fish sucks these larvae in through its mouth, and they travel to the gills where they attach themselves, providing the larvae with food and a safe place to grow up.
6 ALLIGATOR SNAPPING TURTLE
Aggressive mimicry isn’t just for insects – there are plenty of hungry animals using disguises and lures to get food.
A terrifying example is the alligator snapping turtle, which is native to the southeast of the US. It looks like a prehistoric monster – or even a dinosaur – and it’s huge. It can grow to 80 centimetres long and more than 100 kilograms.
Although this big turtle hunts for everything from mammals to smaller turtles, ducks and even baby alligators, it has a rather clever strategy for securing a favourite snack: fish.
All it does is sit on the ground below water – which it can do for as long as 50 minutes without needing to surface for air – and open wide its powerful jaws. It is called a snapping turtle for a reason!
The trick is that the tongue of the alligator snapping turtle has evolved an appendage that is bright red and a very similar shape to a worm. This worm-mimic lure is wiggled about until eventually hungry fish come around to check out what looks like an easy meal. The joke is on them: the fish are the easy meal.
The jaws snap shut, and the turtle has its lunch.