Fly Balls

No, not baseball (although this was the name of my graduate school softball team). And not a reference to non-existent fly scrotums, either.

It’s a description of this photo:

The flies were identified on Entomo-L as Atherix variegata, which is a species of fly that has an aquatic larva (maggot stage).  They are important fish food!

They sometimes go by the common name of “snipe flies”.  The behavior of this Genus is nicely summarized in the journal Psyche.

The adults do something very odd–the females cluster together in this ball when they lay eggs. They usually do this over water–so that when the eggs hatch, they drop down in to the water.

It could be an adaptation to group larval emergence in time and space.  While some maggots will be eaten, the sheer numbers appearing at a short interval in time makes sure that a few will be missed. A giant clump of dead flies also will serve to discourage a lot of predators, so the eggs in the center should hatch safely.

Nifty!

3 thoughts on “Fly Balls

  1. Oh, I know the larvae of these, find them in aquatic samples all the time.

    Never heard of the fly ball before though.

    ~Kai

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