Last week I featured another bizarre caterpillar, Hawaii’s carnivorous Eupithecia, and I thought perhaps this week you’d like to meet a larva that is somehow, impossibly, even more bad-ass.
Denmark’s beautiful Alcon Blue butterfly looks about like you’d expect, for a butterfly. It has lovely blue wings and eats flowers and is about as intimidating as a nice decoupage. But don’t let them fool you. These lepidoptera are devious little bastards.
For the most part, the Alcon Blue’s reproductive cycle looks pretty normal. They get it on, as butterflies do, and then the female lays her eggs on a specific flower that she’s terribly fond of, and then the larvae hatch and hang around eating plants for awhile, and then shit starts getting real. You see, when the larvae are large enough, they drop down to the ground and sit around waiting, while emitting a delicious pheromone-y perfume that makes them smell irresistible to ants. And I’m not talking irresistibly delicious, either.
The scent that the larva emits convinces the ants that the larva is one of their own offspring, and they’ll pick it up and carry it right into their own home. In fact, they are so freaking stoked about this larval caterpillar that they will protect and preserve it at the cost of their own offspring. They feed it, they keep it clean, they make it the happiest little larva in all the land, and they don’t even mind that these faux-ants they’re tending to are eating not only the food they bring in but also they’re devouring the ants’ own larvae, because hey, who needs their own offspring when they can use all their resources caring for the freaking bad seed, instead?
Although this may sound like basically the perfect life for a larva, wherein they are fed and cared for and presumably get to spend all of their time playing Call of Duty, their gambit is not without risks. For one, the ants who are being parasitized might just figure the whole thing out, as this BBC article explains:
By looking at the patterns of infection/resistance and the genetics of different populations, the team was able to describe how the separate chemistries of the butterflies and the ants co-evolve in what amounts to an ongoing “arms race” – giving each animal periods and locations of dominance in their relationship.
So essentially, the ants change their chemical scent to help them recognize the butterfly larvae, and the larvae change their scent to adjust to the new situation, and on and on forever and ever. But that isn’t the only risk the Alcon takes inside the ants’ brood. They’re also preyed upon by a wasp called Ichneumon eumerus. The wasp, upon discovering Alcon larvae within an ant nest, will spray a chemical concoction that causes the ants to become confused and attack one another. Then it will seriously screw up the Alcon’s life; to wit:
When the wasp detects an Alcon caterpillar inside an ant colony, it charges inside and sprays a pheromone cocktail that makes the ants attack each other. The wasp slips through the confusion, lays its eggs inside the caterpillar and leaves. After the caterpillar turns into a chrysalis, the eggs hatch and consume the it from the inside.
Pleasant, no? And this is all while the little beggars are still just little pink slug-looking things. If they survive the wasps long enough to actually pupate — which may take up to two years in the ants’ care, being total freeloaders — their chemical defenses no longer protect them from being seen by the ants as intruders. They then get to run the gauntlet out of the ants’ brood chamber and out into the world. They aren’t without defenses, however; they’re covered in loose scales which detach when grabbed by angry ants, allowing them to make their escape.
You might think that this sounds like a horribly convoluted way to reproduce, and frankly you’d be right; the Alcon Blue lives a very specific life which requires specific plants (they feed from and lay their eggs only on Marsh Gentians and Willow Gentians) and needs ant colonies (though it is somewhat non-specific in which ants will do) to perpetuate its life cycle. Both the butterflies and the wasps that prey on them are considered endangered, which is too bad because there are some scientists who would dearly like to leverage their brand of chemical warfare, but you’d probably think it was pretty good news if you were an ant; it probably gets tiresome being caught in the crossfire between butterfly and wasp.