In this area I heard and saw something I have not heard before. From various locations on this stretch of trailbank (about 15'), I heard short, dry "trills". Camel crickets appeared from under the leaf duff, then went back under. I managed to get a photo of one, but many were relatively pale, like this one. 9:09 PM PDT. It was overcast and a little muggy.
While I didn't witness one of these actually producing the sound, I think what might have been going on is vibrational signalling? Like this perhaps: http://www.researchgate.net/profile/Natasa_Stritih/publication/232649786_Mating_behaviour_and_vibratory_signalling_in_non-hearing_cave_crickets_reflect_primitive_communication_of_Ensifera/links/00b7d52976b8bdbca0000000.pdf

Here is a recording of some of the sounds: https://soundcloud.com/dbrusco/150609mbcamelcrickets