Found abundantly (at least locally) on low-growing non-climbing western poison ivy (Toxicodendron rydbergii). Feeds from underside of leaf, eating ragged holes that bleed latex that turns black. Rearing caterpillars that eat PI requires extra motivation and some care. A forked twig works well to flex over the low plants to search the undersides of leaves that show feeding damage. The early instars are quite translucent and cryptic, but the feeding damage is a sure sign. This photo shows the final instar. Caterpillar dates span all of July at my home. They appear to choose plants under a wooded canopy over those more at the sunny edge. While caterpillars were consistently common to abundant (as far as monitored), only one or two adults were ever captured by BL and MV lights operated frequently, over many years ten feet away. One adult also was captured in a sugar bait trap (possibly by accident?).