I saw this little spider (about 7.5 mm body length) running across a driveway while I was talking to a neighbor. It appears to be Castianeira amoena (female). The movement was very ant-like, in addition to the pattern. I love the tiger-stripes on the abdomen.To me, it resembles a velvet-ant (a type of flightless wasp--Mutillidae) than an ant per se. Velvet-ants are said to have a powerful sting, so mimicry of one of them would make sense.Not initially showing up on EOL where it should, under Castianeira amoena, but it should get there eventually.