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Animalia >Arthropoda >Insecta >Diptera >Tylidae >Rainieria >

Body length 11mm, wing length 8mm. As this fly has white tips on two front legs, it is called "maejiro"-meaning "white front". The fly uses middle and hind legs for walking and front legs like hands. It is a fly that looks like a quadruped with two white hands.
Males exchange aggressive displays on tree trunks. Body size and how wide they can open the front legs seem to determine the winner. When the opponent is larger than itself, a fly retreats and flies away. A winner is generally decided in a very short time.
It is not certain whether exchanges of aggressive displays are related to territoriality. Winner of games do not defend territories to wait for adult females. A female may approach and mate with a male that has not gone through a male-male contest. Copulating pairs are found on a tree trunk where no flies of this species have ever seen. A tree truck may be a "boxing ring" for displays rather than a territory.
When males are about the same size, a fight becomes prolonged one. When they could open their legs equally wide and their height, when they stand with four hind legs, is the same, males may pull their proboscis upward and try to reach up. When this does not determine the winner, a male may push down the head and proboscis of the opponent so as to make the height of the opponent shorter. Losers usually fly away.
This fly species sometimes fights with other insects as well. It chases them by pushing them with the front legs.

(Data No.momo050113rl01b)

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