As friend dbrusco noted,

we've seen clots of this silky stuff for the second year around this date. In about 2 miles of trail through chaparral at around 3600' elevation, I saw around ten instances. Sometimes draped over live foliage, sometimes on dead branches, sometimes right on the ground on the trail. Sometimes strands are a meter long. It seems very likely to me that it drifted down from the air. The stuff is faintly tacky, a bit like teflon tape.

Could this be congealed gossamer, formed when lots of individual strands wrapped around each other in the air, kind of a precipitation process? Can't think of a better explanation, but maybe somebody here can.

A couple of closeups follow.