The thief and the dragon

No larger than a grain of rice, the robber fly has the visual acuity of a dragonfly –an insect 10 times its size


In a classic case of David and Goliath, new research has delved into how the visual adaptations of a tiny fly give it predatory behaviour typical of much larger insects.

The robber fly has similar spatial resolution of the retina to dragonflies – an insect that is 10 times its size.

University of Cambridge lecturer, Paloma Gonzalez-Bellido, told OT that, while the research was at an early stage, she would like to see if a miniature and highly efficient visual system could be developed based on the insect’s eye.

“These findings demonstrate that an animal with a brain no bigger than a poppy seed can evolve visual adaptations typical of large predators,” Dr Gonzalez-Bellido explained.

The research, published in Current Biology, found that the robber flies had an acute fovea, with poorer vision elsewhere.

The insects were capable of detecting prey smaller than 2mm that were up to 100 body lengths away.

The robber flies used a flight strategy, known as a current bearing angle, allowing them to intercept prey without needing to know where the interception would take place.

When flies were 29 cm or closer to their prey, they would decelerate and change their direction to secure their catch – a behaviour known as the “lock on” phase.

“From an optics point of view, the lock on behaviour is intriguing because we do not yet know which visual cue lets them know they are less than 29cm from their prey,” Dr Gonzalez-Bellido highlighted.