Some insects, such as ants, lead famously social lives, with massive colonies of individuals, cooperating for a common good. These insects also tend to have unusually large brains. For over 150 years, this link has been tacitly taken as support for the idea that social animals need extra smarts to keep track of all their many relationships. But Sarah Farris from West Virginia University and Susanne Schulmeister from the American Museum of Natural History aren’t convinced.
After comparing a wide range of species, they think that the large brains of these insect collectives have little to do with their cooperative societies. Instead, their enlarged brains may have been driven by a far grislier habit: body-snatching.
The transformation from caterpillar to butterfly or moth is one of the most beguiling in the animal world. Both larva and adult are just stages in the life of a single animal, but are nonetheless completely separated in appearance, habitat and behaviour. The imagery associated with such change is inescapably beautiful, and as entrancing to a poet as it is to a biologist.
According to popular belief, within the pupa, the caterpillar’s body is completely overhauled, broken down into a form of soup and rebuilt into a winged adult. Richard Buckmister Fuller once said that “there is nothing in a caterpillar that tells you it’s going to be a butterfly.” Indeed, as the butterfly or moth quite literally flies off into a new world, it is tempting to think that there is no connection between its new life and its old existence as an eating machine.
But not so. A new study has provided strong evidence that the larval and adult stages are not as disparate as they might seem. Adult tobacco hookworms – a species of moth – can remember things that it learned as a caterpillar, which means that despite the dramatic nature of metamorphosis, some elements of the young insect’s nervous system remain intact through the process.