Only Our Second Time With Painted Lady Caterpillars

Painted Ladies (Vanessa cardui) are some of our most widespread and common butterflies, and yet finding the two caterpillars today will only make our second time ever rearing them.

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The Painted Lady (Vanessa cardui) is one of our most very well known, showy and popular butterflies. It even rivals the infamous Monarch (Danaus plexippus) in children's butterfly kits and classroom pets. And there is a good reason too; it has the widest range of all of our Vanessas and is considered the most cosmopolitan butterfly in the world (its also found in Europe, Asia, Africa, and Central America)! 

But here in the Bay Area, at least in Albany, the smaller West Coast Lady (Vanessa annabella) is much more common. We have found their caterpillars infesting the wild mallows (Malva) and have had the chance to raise well over a hundred of them over the years. The Painted Lady is supposed to also be in our region, but we have only ever encountered and reared its caterpillar a single time before today. It's actually a pretty funny story. Some time ago, maybe two years ago when we reared a ton of West Coast Ladies, we happened to discover that one of our caterpillars was significantly larger then the rest. It looked pretty much identical, but for some reason it was enormous and ended up making a huge chrysalis as well. At the time, we were pretty confused and just thought that it was simply variation in the species and counted ourselves lucky for having reared such a large one. But when it emerged, we quickly realized that it wasn't a West Coast Lady at all; it was a Painted Lady! 

Truly, West Coast Ladies and Painted Ladies look very similar. The caterpillars and chrysalises look almost identical except the latter is usually larger in size, of course. The butterflies also look similar but the West Coast Lady tends to have much more angular wings. A good way to distinguish the caterpillar of our Vanessas is by host plant since they each prefer their own group of hosts (thistles [Compositae] for Painted Ladies, mallow [Malvaceae] for West Coast Ladies, nettles [Urticaceae] for Red Admirals [Vanessa atalanta], and everlasting [one tribe of Compositae] for American Ladies [Vanessa virginiensis]), but of course this was impossible since we had found the Painted Lady caterpillar on mallow like the rest of the West Coast Ladies!

Anyway, today when we went to pick leaves for our Pipevine Swallowtails (Battus philenor) at Tilden Regional Park in Berkeley, CA, we also decided to take a little hike on one of the trails to see if we could catch any butterflies with our new net, especially the Western Tiger Swallowtail (Papilio rutulus) we have been chasing this whole year. When we first got there, we found a Painted Lady flying around some trees but it was too fast for us to catch. But later, when we actually got onto the trail, we saw a whole bunch of milk thistles (Silybum marianum) growing along the dead grasses, a typical Painted Lady host. Actually, we didn't really expect to find anything there and didn't actively search any, but when we went to catch a Common Buckeye (Junonia coenia) and take some photos of some Acmon Blues (Plebejus acmon), we just so happened to stumble upon a thistle that was completely covered in caterpillar nests and huge frass. It seemed that most of the caterpillars that used to inhabitat them had left and pupated because we only found two Painted Lady caterpillar, one of which we think is in fourth instar and the other in second. 

When we got home, we had a hard time finding some more milk thistle for them to eat. There used to be a ton growing in our backyard, but now it is gone for some reason. When we went down to the Ohlone Greenway where we saw a bunch in the spring, there was also none because they had all been cut down. Eventually, we did find a tiny patch that was hard to identify as milk thistle since had been cut down so badly. But when we offered a leaf to the caterpillars, they readily accepted it so it must be. Hopefully we can keep them alive and they are not parasitized!

- Brian