Things aren't always as they seem in the jungle. As the sun was setting and we were heading back to the Tambopata Research Center, Chris Johns made a very cool spot. At first it appeared as if two ants were stuck together on a branch...but upon closer inspection we realized that we were dealing with an ant-mimicking spider feasting on its ant prey.
The mimic in this case is a neotropical crab spider Aphantochilus rogersi (right). It is an incredible mimic of Cephalotes ants (its prey on the left). Chris and I had to count the legs to be convinced it was really a spider. This type of ant-mimicry is known as myrmecomorphy, as these spiders have evolved morphological and behavioral characteristics to resemble ants.
Myself and the December team photographing some arthropods 'Meet Your Neighbors' style.
But why did this ant-mimicry trait evolve in the spider? Well let's break it down:
- Ants are often equipped with chemical defenses and have lots of sisters to defend one another. This makes them risky prey items for a predator.
- Spiders, on the other hand, are usually solo and make a juicy meal for a predator, like a bird.
- So, if spiders become selected over evolutionary time to appear more like ants, it could trick visual predators into avoiding them. This is known as Batesian mimicry: when a harmless species has evolved to imitate the warning signals of a harmful species.
However, as pointed out in the comment thread in Alex Wild's post on these spiders, Cephalotes ants have pretty good vision. So if the spider was less convincing in its mimicry, the Cephalotes ants might be able to avoid the predator before it gets too close. It could be that this spider evolved to look like Cephalotes ants for both reasons: to trick the ants, and to trick visual predators.
So the next time you find yourself walking around nature, just remember: things aren't always as they seem.
Citation: Castanho LM, Oliveira PS (1997) Biology and behaviour of the neotropical ant-mimicking spider Aphantochilus rogersi (Araneae: Aphantochilidae): nesting, maternal care and ontogeny of ant-hunting techniques. Journal of Zoology 242: 643-650.
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