Believe it or not, those two eyes staring at you are not eyes; they are two breathing holes. What you see isn’t a face either; it’s the backside of a blow fly or calliphorid larva. This is the latest in animal mimicry that the international research group led by Roger Vila (Institute of Evolutionary Biology, IBE:CSIC-UPF) has come across. This larva disguises itself as a harvester termite – those that come out of the termite mound to the surface to cut grass – in order to enter the mound with them and live there.
The larva has evolved to look so much like termites that they recognise it as part of their colony. It’s not just the false face; the blow fly has developed several mechanisms to become fully integrated. For starters, it has termite-like antennae and palps. It also has appendages, not usually seen on fly larvae, which perfectly mimic the antennae of wood-eating insects. With these, the larvae communicate with several termites at once. But the larvae have not only changed their physical appearance, they have also changed their insides: the smell they give off is exactly the same as that of the termites in the colony they enter. In this way, they trick the soldiers so that they do not attack them. Thus, the blow fly larvae blend in and let the termites take care of them, groom them and feed them.
The discovery was fortuitous and reached everywhere in the world. When the research team was looking for anthills in the Anti-Atlas mountain range in Morocco, they lifted a stone and, instead of ants, they found the termite mound with three larvae almost on the surface. When they studied them in the lab, they found that the larvae settle where there are more termites, which are constantly taking care of them. However, the team has not been able to see how they transform into adult flies, as they died before metamorphosis. Now, they are working to fully understand the relationship of this strange pair.
Although adult hump-backed flies have previously been seen settling on a termite mound, this is the first time it has been seen in this species of fly. This suggests that this is a new form of social integration, and one that has been carried out very quickly. What more evolutionary surprises will they have in store for us?
Schär S, Talavera G, Dapporto L, et al. Blow fly larvae socially integrate termite nests through morphological and chemical mimicry. Current Biology. 2024; https://doi.org/10.1016/j.cub.2025.01.007
