A flying aquatic insect.

As the air grew warmer, dragonflies lost the brightly colored patches on their wings, which helped deter predators and played an important role in the dragonfly’s mating rituals. The remaining dark patches absorbed heat, damaging the wings and disrupting the dragonfly’s reproductive patterns.

For a time, the dragonfly population was drastically reduced, but the temperature stabilized and they managed to evade extinction. However, a new challenge appeared: pollution in the water of the stream was harming dragonfly eggs.

The few dragonflies that kept their wing patches now had an evolutionary advantage. Dragonfly females developed a hormonal mechanism that affected the wing patches and changed their density. This mechanism has to do with the dragonfly’s reproductive cycle (it plays a role in mating rituals), but it is also a new way for the dragonfly to communicate with the shrimp that live in the water. The shrimp have the ability to purify polluted areas in the stream.

The dragonfly’s new trait changes the density of the female’s wing patches around the egg-laying phase of her life. The dense patches reflect ultraviolet rays onto the water, signaling to the shrimp that live in the water. Drawn to the area where the dragonflies lay their eggs, the shrimp clean the water, enabling the dragonfly’s young to hatch and develop normally.

Josh Milwer, Nitzan Friedman