Found beneath lose bark of fallen, decaying sugar pine (Pinus lambertiana).
Appears to fit the description for Theatops californiensis (in part because of site): 21 segments, each with a pair of legs; last segment longest, with thickened pincerlike hindlegs.(source: Evans, 2007 (1))
ID confirmed by Rowland M. Shelley (North Carolina State Mus. of Nat. Sciences), in communication with Jim Hogue (CSU Northridge).
"Clearly distinguishable by the large, heavily sclerotized, forcipulate caudal legs; also note the elongate 21st tergite right in front of these legs, which is clearly longer than other tergites on the animal." (Rowland Shelley)