Colorado Rainbow Scarab - Zoology Object (May 31, 2011)

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Up to a whopping 22 mm in length with bright metallic green coloration, the native Rainbow Scarab, Phanaeus vindex, is the largest and most spectacular of the about 90 dung beetle species inhabiting Colorado. It is rarely seen because it spends its time under cattle and bison dung pats working on its nest. It digs tunnels under the dung pat and pushes dung portions to the end of those tunnels as food for its larvae. Only the males have the long horn on the head. DMNS Curator of Entomology, Dr. Frank Krell, found this specimen at Chico Basin Ranch in El Paso County on May 14, 2011. It is a new county record for this species.

In ecosystems with large mammals dung beetles are a crucial component of the nutrient cycle by being responsible for breaking up dung and reintegrating dung portions into the soil. Compared to other grassland ecosystems, the dung beetle fauna of the North American plains is currently rather poor, and is heavily invaded by European species. The dung recycling seems to be rather incomplete. When 30-60 million bison had roamed the Great Plains and produced at least 100-200 billion dung pats per year, a more abundant dung beetle fauna can be assumed, with large dung rollers or the Rainbow Scarab having been present in much higher numbers than today. The dung beetle fauna of Colorado and other grassland ecosystems world-wide are studied in-depth by the Entomology Program at the Denver Museum of Nature & Science.

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