Sunday, March 26, 2017

Bristletail in the Moss


We spent several hours on Tuesday exploring the mosses of Bull Creek with Nels Holmberg, a bryophytologist, but more on that in the next blog.  Identifying moss, or in my case acting like you might be able to, requires a lot of close ups with a magnifier or a macro lens.  As I was leaning into a cliff face covered with moss, I saw something less than an inch long crawling among it.  I got one picture of it before it disappeared into the microscopic forest.

Back home, I enlarged the picture and was facing a relic of ancient times.  After a search, I tentatively called it a bristletail and sent it off to Chris Barnhart who identified it as a Rock Bristletail (RB), Meinertellidae.  This is a small family of primitive insects belonging to the order Archaeognatha.  The Archaeognatha ("ancient jaw") are among the most ancient living insects, appearing in the early Devonian period 400 million years ago long before plants produced seeds and reptiles evolved.

RB anatomy has a lot of interesting features.  Its segmented body has a distinctive arch on the back of the thorax.  The head is flattened side to side and is equipped with a flexible jaw that can rotate and twist around.  It eats primarily algae, but also lichens, decaying organic material and of course moss.

 Rock bristletail on rock - Bruce Marlin CC
The most interesting feature is its three tail-like appendages.  It has a long epiproct between two smaller cerci.  Using this handy accessory it can spring up to 12 inches into the air to escape a predator, or presumably just for the fun of it after a boring day in the moss.  My favorite Bug Lady describes how it can use its epiproct as a rudder to direct its landing, much like a flying squirrel uses its tail.  Dr. Stephan Yanoviak studied this by dusting bristletails with orange fluorescent power to track their movement.

At the time I was disappointed that I couldn't catch it to study closer.  Thinking about it now, it is nice to have this primitive creature remain somewhat mysterious, maybe for another 400 million years.

The Bug Lady's Bug of the Week is as entertaining as it is educational, a must read.
Thanks to Dr. Chris Barnhart for the ID.

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