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At the mating of the dance flies, the females make themselves more attractive by swallowing air and laying their hairy legs along the body, to look like they have many eggs. New research shows that the males have developed better vision, probably in order to reveal the bluff.
1 / 3foto: John Alcock
Hone flies attract males by inflating their stomach. The males in turn sharpen the sight to see through the bluff.
– We believe that it is an ongoing evolution where both genders try to outlast each other, says biologist Axel Wiberg.
Together with researchers from, among others, the University of Gothenburg, Axel Wiberg, development biologist at Stockholm University, has studied dance flies mating game. When they are mating, the females swarm in large groups and the males come from below the swarm and look into their potential partners. In order to increase their chances of spreading their genes, the males are aiming for female flies that appear to have many eggs.
– You usually see that by having a big stomach. In this case, the females also have larger legs with more hair to look big and powerful, says Axel Wiberg, one of the researchers behind the study.
Protein supplement in gift
Before the mating, the male flies also have a gift with them, usually a dead insect, which they hand over to the females. The female flies rarely chase themselves, but they need protein to produce eggs. This is where the trixing begins – by fake that they have eggs, they can fool food even though they have none.
– The females have tricks to look like they have many eggs. They swallow air that fills their stomachs, and to look delicious as they swarms they have developed hair on their legs and the wings can be bigger and darker, says Axel Wiberg.
Appearance important
The fact that animals imitate, behave and have special looks to attract the opposite sex is nothing new, it is common not least among birds, where it is usually the males that are decorated. But now the researchers have seen that in the species where the female flies developed the most hairy legs, the male flies have the most enlarged eye facets. The facetes are the small individual eyes that insects see.
– We believe that there is a connection and that they have developed in interaction, says Axel Wiberg.
The researchers believe that this sexual game can lead to a development of the species, but if the males with better views actually manage to see through the scammers, the researchers do not know yet.