Red Flat Bark Beetle

 

The leaves are slowly trading their chlorophyll for fall colors and the mornings in the valley are creeping toward freezing.  Thus begins firewood season, the time to start cleaning up downed logs and branches that have piled up in the grass and thickets along the road.  It is also when I start finding more creatures that live in the frass and fungi under the bark.

The bark peeled easily off a long dead log, revealing the many tracks of bark beetle larvae and other denizens of the dark under bark world.  Centipedes scurry away before I can photograph them and tiny jumping spiders tease me, pausing for just long enough to start to focus on them before bounding away.

Eyes bulge out the side of its head - REK

Another chunk of bark yields a treasure.  Bright red, it lays still in a track of frass.  It is striking in this world of dark brown, seemingly unaware that it stands out in the light of day.  This is a red flat bark beetle, Cucujus clavipes.

It is the largest of the flat bark beetles but measures less than a half inch long.  Its flattened body is an advantage when it comes to traveling the tunnels under the bark created by other larval prey.  It is bright red including prominent femurs, with black antennae and legs.  Its eyes bulge out the sides of its head.

Note red femurs with black legs - REK

For a beetle said to be common, there is surprisingly little known about it.  It can be found under the bark of recently felled deciduous trees.  In this hidden world, its eats in private, presumably munching other arthropods or worms.


The larva is also flatbacked.  When I peeled back the bark I would get a fleeting glimpse of flat brown insects looking like legless centipedes.  They had legs in front and although they were not fast, they disappeared into tunnels before I could focus on them.  Finally I was only able to get the slightly blurred picture on the right of one escaping. Fortunately I have Tom Murray's picture to fall back on.

tom murray

While little is known about their under bark life, their winter survival in Alaska is rather famous.  A lot of research has been done on their ability to tolerate supercooling in harsh arctic environments.  C. clavipes puniceus is reported to be able to survive temperatures at -70F by producing glycerol and sorbitol antifreeze chemicals.  A later study showed that some individual larva could tolerate even greater cooling by decreasing its water content.

Peeling off some dead bark can expose intriguing patterns of insect larval tunnels.  There is a lot more you can learn in Charley Eiseman's book Tracks and Signs of Insects and his Bugtracks blog.

Fall is a good time to roll over rotting logs to look for signs of life in the underworld.  Just remember to roll them back in place.  Leaving it exposed is the equivalent of running a bulldozer through their neighborhood.

Animal, vegetable, mineral or other?  You decide.