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Sunday, December 30, 2012

A Bug Walk in December

The ground is finally covered in a blanket of white, fluffy snow… it’s a perfect day for a bug walk!  Not surprisingly, there are few insects out in the sub-freezing temperatures of winter, but a hardy few are specialized to take advantage of the snowy conditions.  Even at temperatures as low as 20 F, there are still some insects moving about.  Their dark bodies contrast with the white carpet of the forest, making them easy to spot.  On your next snowshoe walk, keep an eye on the snow and you may be lucky enough to find one of these fascinating creatures:

This tiny creature, commonly called a snow flea, is only about 4mm long.  Despite its name, it is a springtail, not a flea.  This individual is in the genus Pogonognathellus, but it is not the only springtail that is commonly active in winter.  They are often seen in large numbers at the base of trees, as if someone sprinkled pepper onto the forest floor.  Some theorize that certain springtail species actually migrate as they jump across snow, taking advantage of this nearly predator-free habitat to find new food sources. 

This insect is often called a “snow fly” (Chionia sp.) since it is most frequently seen walking across the snow.  Ironically, this fly cannot fly.  In the cold temperatures that it thrives in, it is difficult to keep wing muscles warm enough to function, so this fly has lost its wings altogether.  It can even be found mating atop the snow!

Numerous species of spiders can be found crawling on top of the snow.  Some even build webs in the freezing temperatures to catch other winter-active insects!  But no spider will wander too far from an “escape.”  Subnivean (under the snow) temperatures are within a few degrees of freezing throughout the winter; this make the perfect retreat for when it gets too cold for even the hardiest of insects. 

One of the oddest discoveries on a December bug walk near NBNC was this beetle larva, which was found crawling across the snow.  After we posted the image on bugguide, it was identified by Dr. Margaret Thayer of the Field Museum as a rove beetle (Tachinus sp.).  “Odd behavior,” commented Thayer, “we haven't really heard of them being winter-active.”

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