Years ago I planted a New Jersey Tea sapling, Ceanothus americanus. It's such a shame most of the mail order nurseries sell this shrub as a 4inch plug. It would really be nice to get it as a quart or gallon size pot instead of treating this like something you'd install in a meadow garden, to be mowed or burned at a later date. NJ Tea is a nice little shrub with a 2' to 3' round habit. It's touted as a hummingbird plant, not because of the flowers, but because of the droves of tiny insects that come to pollinate it. When flowering, these plants are absolutely swarming with little bees and solitary hunting wasps that are overall beneficial to have in the garden. Sadly, despite distribution charts showing how common this species is all across the eastern US, it's in something of a dramatic decline and becoming very hard to find in the wild.
Part of the problem was that farmers used to believe this plant was a sign of good soil and bulldozed whatever habitats it grew in for farm land. Where it still grows today, it's easily shaded out by tall perennials and encroaching forest land.
Western Ceanothus species and their bright blue flowers tend to get a lot more honeybee attention so I guess this isn't entirely unexpected. Sadly I don't know of any western Ceanothus that's hardy in New Jersey or I'd have tried growing it by now.
It's a complex life style for sure. I theorize that not all species of ants are ideal to overwinter inside of. Some of the species that are more finicky about their host plants are uncommon or endangered, such as the Karner Blue Butterfly, which only lays eggs on Lupinus perennis.
So if I get a chance to I'll try and photograph the caterpillars, ideally with ants tending them but I can't promise anything. The eggs she laid were almost microscopic and the caterpillars are absurdly small. Also later instars might prefer consuming ant eggs once they're inside a nest so I may have to setup a fragment colony.