Biting flies confuse blue objects for food, finds new research

The study said if mechanisms that attract flies to coloured traps are unlocked, it will become possible to catch them efficiently, which will curb spread of fatal diseases.

Biting Rhagionid fly | Wikimedia Commons

New Delhi: Biting flies’ affinity to blue objects is associated with their confusion about the colour for an animal to feast on, recent research has concluded.

The study, published in the Proceedings of the Royal Society journal, looks into why biting flies are attracted to blue objects. The researchers from Aberystwyth University’s department of life sciences, led by Roger D. Santer, elaborate on how these flies are unable to distinguish between artificial blue stimuli and animals.

Previously, biting flies’ attraction to the colour blue was exploited to prepare fly traps and fly control mechanisms. However, the reason why flies are drawn to blue has remained a head-scratcher. There were three key lines of reasoning proposed to explain the attraction: One, to these flies, blue resembles shaded resting places; second, they confuse the colour for animals; and third, the blue attraction happens because of the polarization of light.

During the research, Santer and his team created artificial neural networks (ANN) that mimic the visual processing that goes on in the brains of flies such as the tsetse, stable, and horse fly. Artificial neural networks are a form of machine learning inspired by the structure of real nervous systems. They trained these ANNs to distinguish between animals and leaves and between shaded and unshaded areas. When these networks were presented with artificial blue stimuli, it was found that ANNs could not distinguish between blue-coloured objects and animals.

On the other hand, ANNs had no difficulty differentiating between blue objects and shaded areas and did not confuse colour for shade.

Santer said that if they can understand the mechanisms that attract flies to coloured traps, it will become possible to improve the colour of those straps so that they more efficiently catch flies.

“This is a really important aim because different species of biting flies spread diseases of humans and animals, like human African trypanosomiasis (sleeping sickness), which is endemic in sub-Saharan Africa and without treatment is generally fatal.”