Subject: False-eyed caterpillar in San Diego County, California
Geographic location of the bug: Oceanside, San Diego County, California
August 25, 2017 4:27 PM
Hi! I found this little critter outside my front door after I was away for a while. (There’s a large tree beyond the sidewalk, so it could’ve easily fallen there.) It didn’t want to move, so I had plenty of time to get a good shot.
It had green/grayish skin. It seemed that it was trying to change its skin color to match the pavement below it. I left and came back to find no trace of it. I wonder if a bird spotted it…
Anyway, what kind of caterpillar is this? I haven’t seen it before and it has false eyes that extend further inward than the ones I’ve seen pictured on this site. I’m on USA’s west coast, in Southern California. (We also have green jewel-scarab beetles that fly around in the daytime here. Not sure if that helps.)
Based on your location, we are leaning towards this being a Western Tiger Swallowtail Caterpillar, because of this BugGuide image. BugGuide states: “Larvae very similar to those of Pale Tiger Swallowtail, but black pupil of false eye-spot larger, and yellow spot inside eyespot entirely separated from it, not just notched.” BugGuide also states: “Larvae feed on foliage of deciduous trees, including cottonwood, birch, elms, willow, alder, sycamore, and aspen.” When it was still feeding, this Western Tiger Swallowtail caterpillar was green, but as the time for transformation into a chrysalis approached, it darkened to the brown color your images depict, though some individuals turn orange. Caterpillars often travel away from the food source to find an appropriate place to undergo metamorphosis. The similar looking Two Tailed Swallowtail Caterpillar is another possibility for your critter’s identity.