Rhagium mordax (Degeer, 1775) This cerambycid beetle (Coleoptera: Cerambycidae) is a very fast walking one that is called the
"barklöpare" in Swedish (bark runner) and is 13 to 23 mm and its larvae feed on deciduous trees (Birch in this
area). The beetle is usually slightly larger than the similar looking R. inquisitor L. that is 9 to 22 mm long
and feeds on Norway spruce and Scots pine.
Individuals of both species often run rather fast and then stop with their head up and antennae out as if very inquisitive (hence the name of the second species not shown
but for a photo see: R. inquisitor).
For another site on cerambycids:
more info on R. mordax at http://marilyn.uochb.cas.cz/~natur/cerambyx/rhagmord.htm
more info on R. inquisitor at http://marilyn.uochb.cas.cz/~natur/cerambyx/inquis.htm
Images © 1996 by John A. Byers, Chemical Ecology