beetles feed on mosses but Amphicyrta doesn't fit this pattern so much. I found A. dentipes partially buried in the riparian litter of dead twigs and dark soil. The other Amphicyrta species in California (the brassier looking A. chrysomelina) is known to feed on lilies and other vegetables and can sometimes be a pest (although I doubt very much that you'll ever find an insecticide label with a pill beetle listed on it).
The habitat along Big Creek is a bit unusual for a mid-elevation Sierra stream (at about 3,000 feet). It flows fairly slowly and has sandy banks in several places. I also found several ground beetles in the same area (including the impressive Pterostichus lama).
A bit further up the road I came upon a wild apple tree at dusk with ripe fruit. It was a very pleasant surprise and not something I see very often – especially in California where we have no native apples larger than a crab apple. I sampled a few of the less-wormy fruit. They're not as bitter as crab apples but not so sweet as fruit-stand varieties (like Red Delicious for example). They're also smaller but I enjoyed them much more than I've enjoyed apples in years. I kept thinking of Thoreau's essay on wild apples.
And indeed Thoreau is right. I brought a small bag full home with me and nobody liked them at all. But I’m secretly saving the seeds anyway.
Johnson, Paul. Project Byrrhus (www.sdstate.edu/ps/Severin-McDaniel/project-byrrhus/index.cfm). Accessed October 12, 2010.
Thoreau, H.D. Wild Apples; in Henry David Thoreau, Collected Essays and Poems. The Library of America, Second Edition, 2001.