Day eyes do not stop hornets from flying at night

Hornets are the largest members of the wasp family but, unlike most insects, they can fly both during the day and at night. Intrigued by this unusual behaviour, researchers at Lund University investigated the eyes of the hornet to try to understand how they were able to see both during the day and at night. To their surprise, however, the researchers found no special adaptations that would allow the hornets to see in dim light.

Flying insects rely on vision to control flight, avoid obstacles and to find food and mates. For day active insects, such as honeybees and wasps, using vision to control flight does not pose any great problems because of the bright light provided by the sun.

However, to be able to use vision at night, the eyes of insects must be well adapted for capturing the small amounts of light that are available.

To try to find the secret of the hornets’ unusually long working hours, the researchers compared the eyes of hornets with the eyes of their closely related day active cousins, the common wasp.

Interestingly, apart from their larger size, the eyes of the hornets were very similar to the eyes of the wasp in terms of the structure of the eye and its optics. It is therefore somewhat of a mystery how the eyes of the hornets are able to capture enough light in order to see and fly at night.

The researchers suspect that, instead of making their eyes more sensitive to light in order to be able to see at night, hornets have increased the sensitivity of systems that process visual information within their brain.

Full article: Nocturnal insects use optic flow for flight control, published on Biology Letters.

Source: Lund University