EPOW - Ecology Picture of the Week

Crab in the Flower

Goldenrod Crab Spider (Misumena vatia), Family Thomisidae
Black Spruce Forest, Fairbanks, Alaska USA

Explanation:  There be crabs here!  Well, more precisely, a crab spider.  Even more precisely, a goldenrod crab spider (so-named because it often hangs out in flowers of goldenrod plants). 

Goldenrod crab spiders are widespread throughout North America, northern Asia, and Europe.  This week, we are in a dense stand of black spruce in central boreal Alaska, on the campus of University of Alaska in Fairbanks.  

The home of this week's star is the brilliant bloom of
shrubby cinquefoil, Potentilla fruticosa.

Apparently, goldenrod crab spiders can change color between yellow and white depending on the color of the flower they are using as camouflage.  Quite the trickster!  But how exactly it changes color is still not fully understood.  

Notice how incredibly cryptic this arachnid is, in the above photo,
hiding in plain sight among the stamens of this flower!

Their venom is fatal to insects, but is mostly harmless to humans except perhaps for some rashiness and itching.  

This individual -- differently colored than the one hiding in the cinquefoil, above --
is weaving a thin web in the twigs of this dwarf birch (Betula nana),
a common understory plant found in these Alaskan black spruce forests.

 
Information:
     Riou, M., and J.-P. Christidès. 2010. Cryptic color change in a crab spider (Misumena vatia): identification and quantification of precursors and ommochrome pigments by HPLC. Journal of Chemical Ecology 36:412-423.