Image from the Red Admiral and Painted Lady Research Site. I hope they don't mind me using it but these butterflies are so darn hard to photograph. For those of you not in the know, we are in the middle of the Red Admiral and Painted Lady Butterfly Migration. This is one of the lesser know migrations and with good reason. They all fly so fast that people barely notice them. Heaven help you if you're trying to get a picture of one, because unless you have the right conditions they're not stopping for anything.
The range of host plants includes assorted nettles, mallow, which might refer to hibiscus, and pussytoe (aka cudweed). None of which are very commonly used in the garden except for the hibiscus. Nettle is just a weed and often covered in spines, and just pussytoe is overlooked mostly but makes a nice ground cover.
Adults feed on a range of nectar, rotting fruit, and patches of sand where they sometimes gather and sunbath. Supposedly all of these butterflies have it in them to over winter in the adult stage. The survival rate though isn't that great so when temperatures warm up the southern populations suddenly have to repopulate most of the northern hemisphere. Lots of websites say these butterflies have flare ups ever 7 to 11 years... but I've herd people say that's kind of a myth. There is some truth to it but it's not set in stone that every so many years comes the big migration. They have good years; they have bad years; and some years they have massive populations. It doesn't really fall in any measurable pattern.
Personally I've been seeing tons of Red Admirals darting through my yard. Dozens of them pass by every hour. The thing is they do it so fast I can't take pictures of them. So this has inspired me to set out a tray of rotting fruit. I think that would be the better way to go because they're a little picky about what types of flowers they go to. Their most popular plant of choice blooming right now is the nonnative Butterfly Bush which mimics the odor of a rotting tray of fruit anyhow. Coneflowers are another one they like but those are nowhere near blooming.