Wednesday, September 21, 2011

Wood Beetle

While looking for fungi at the Missouri Mycological Society (MOMS) foray at Mingo, I turned over a log which disintegrated in my hands, exposing 20 plus large orange beetles.  After a quick perusal of Bugguide, I emailed Chris Barnhart to save time.  He pointed me to the Passalidae family.They looked familiar, resembling the Bess Beetles I wrote about last November
Mites under front legs
Those specimens were Horned Passalus - Odontotaenius disjunctus, also known as Bess Beetles and Patent Leather Beetles for their pitch black shiny body. These however were bright orange although they were packed together like the previous bess beetles.  The shape, size and parallel grooves down the wing covers were identical.  When I turned them over, there were the familiar mites almost invariably associated with their family of Passalids.  Information on the fascinating mite farming of many beetles can be found at the Macromite site.
Horn of horned passalus
A closeup side view showed the distinctive feature that gives them their other name, the horned passalus.  While holding it for pictures even I could hear its little soft squeaks as it struggled for freedom.

The puzzle of it color remained.  It took eight sites on Google to find the answer.  The Featured Creatures site of Florida University says:

Mature dark horned passalus

"These young adults lack the characteristic black shell of the species, and instead have a red coloration when they emerge from the pupal stage. This red color slowly darkens to black, at which point the insect is considered a mature adult (Schuster and Schuster 1985)."
Knowing this I dug around the bag of ground up wood and beetles I brought back and sure enough, there was an older sibling I hadn't seen before which was very close to black.  This proves once again that color can be deceptive when trying to identify species.

Both the last November blog and Featured Creatures have more detailed information on the interesting life cycle of these decomposers of wood.  They only eat dead wood and thanks to them, bacteria and fungi, they enrich the soil.  Without the decomposers, we would have dead logs hundreds of feet deep in our woods.  Bless their little orange and black bodies.

No Beetles were killed in producing this blog.

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