Hammer Eyed Fly (Richardia telescopica)

On September 9th 2001, I encountered this hammer-eyed fly (Richardia telescopica) on STR trail (~600m mark) at La Selva Biological Field Station in Costa Rica. I was rushing on my bicycle to my field site one morning. I had to make an abrubt stop because my path was blocked by a tree fall which I believe was a Hampea appendiculata (Malvaceae). I noticed the fly on one of the branches of the downed tree. I rushed to get the camera out and set out the tripod. My first thought was that it was the famous star of sexual selection frequently seen on biology text-books: the stalk-eyed fly – Cyrtodiopsis dalmanni – (but what do I know about flies anyway?). One thing I was completely sure was that because of the exaggerated eye shape it was a male. I was only able to capture this short 54 second clip. During this short encounter the fly made a full turn exposing his body from all directions. Movement of halteres which have evolved as flight control organs were quite visible. I don’t know why he was moving his halteres even though he was stationary. Was it a reflex or an active sensory movement?

This dipteran is rather rare to encounter in natural setting. Seredipitous downing of a tree could have brought it to my view only for a brief amount of time.



  1. Erinc Sahin says:

    I had no idea stalk eyed flies inflated the base of their eyes into long tubes by forcing gulped air into their heads, before their exoskeleton hardens. One of the more surreal examples of the freak show that we call life…


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