Worm Things.. WTF?

My wife recorded these in 2006. She walked past them thinking it was a big worm, but as she looked closer she found these.. We looked them up but I don't remember what they are and I'm too lazy to try to find them again. They are some kind of Larva if I remember correctly. This happened in the monsoon season and is the first and only time we have ever seen them. We look around every year but they have not returned. She takes video of 2 groups. There are more like 100 or more groups but they are really hard to spot once they move off the sidewalk and into our yard, which is mostly dead oak leaves and gravel in that spot. Luckily, they had a trail going across our yard and into the neighbors yard, all in a line, separated by about 2-3 feet between groups.