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Bess beetles

Aulacocyclus edentulus


Under a large rotting eucalyptus log. Each adult beetle was about 35mm long. Larvae were slightly longer. One adult was black and the other was a red-brown but otherwise they appeared identical from above. ?


Under timber in suburban back yard.


This spotting is possible evidence that this species might show variable colours? Random or sexual dimorphism?
Two important ID features here are split elytra (flight capable) and a short, grooved, upward curved, blunt facial horn.
subfamily: Aulacocyclinae
genus: Aulacocyclus
Also this is a great page of inputs re Bess beetles vs. 'Horned passalids"

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ChunXingWong 5 years ago

You are welcome Mark.
All I did was just reply to your comment on my spotting :-)

Mark Ridgway
Mark Ridgway 5 years ago

Thanks Chun and Tamara for making me research this properly. It has an ID.

Mark Ridgway
Mark Ridgway 5 years ago

Thanks for the input Tamara. It's certainly not easy to find accurate information online about these even though many people know them.

My son loves these beetles and has studied them for several years. We believe the reddish brown "Bessies" are immature adults, and darken to black as they mature.

ChunXingWong 5 years ago

Passalids definitely look alike all around the world.
You are lucky to get both colors in one spotting.

Mark Ridgway
Spotted by
Mark Ridgway

Melbourne, Victoria, Australia

Lat: -37.90, Long: 145.31

Spotted on Sep 29, 2013
Submitted on Sep 29, 2013

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