Hammerhead or stalk-eyed fly.

Stalk-eyed fly (Richardia suspected.) This is the male -- the female has shorter stalks. I've read that males use the eye stalks to shove each other about when competing for females. When these flies leave their pupal stage their optic nerves are coiled and their eye stalks are much shorter. They apparently inflate the eye stalks by pumping air into them.

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