Why do flies like fruits

A rotten fruit in Polynesi was dubbed the " vomit fruit " because it could cause most enemies to run away, except for a fruit fly.

Now Japanese scientists claim they know why. This fearless insect has special genes that allow them to bypass the plant's odor defense system. Thus, flies can eat rotten plants and nest nearby.

The formidable tree is a shrub ( Morinda citrifolia ), which grows in Polynesia, Asia and parts of Australia's northern tropical region. Most flies stay away from this tree, because of its ripe smell, which is made of hexanoic and octanoic acids, can't be smelled. Particularly, flies of the species Dresophila sechellia are tolerant. They eat the fruit and lay eggs on it, making sure the meal is full for the children.

By gene analysis, scientists found that Dresophila sechellia had two olfactory genes - Obp57d and Obp57e - different from the corresponding genes in other fruit flies.

"For the first time, we found genes that determine the insect's preference for its host , " said Takashi Matsuo, a member of the research team at Tokyo Metropolitan University.

Researchers hope this discovery could help fight harmful insects.

The tree has stinking fruits.(Photo: mytho-fleurs)

T. An