I saw about a dozen of these caterpillars in my yard last night being active/eating around 10PM. By morning, they were all gone (escaping the heat, perhaps). Although I live in the central part of the city, there is quite a bit of natural Sonoran desert landscaping in the neighborhoods around my home, so there are lots of local critters in the area. These caterpillars were hanging out in the weeds that have popped up in my yard over the course of the monsoon here. The caterpillar was a brownish color, with eye spot markings down the side, and a small horn in the back.