A few butterflies do overwinter in leaf litter. These include Duskywings, Viceroys, Hackberry Emperors, and Tawny Emperors. The host plants they might be found around would be Baptisia australis family, hackberry trees, oak trees, and Willow trees. Several BFs overwinter as chrysalides including members of the Swallowtail family. Their chrysalides could be found anywhere, as they can travel quite a distance to find a place to pupate.

This is not a complete list by any means, just a few that are most familiar, and likely to be found in and around gardens.

I don't know of BFs that pupate inside hollow stems. Other insects might do so. I find lots of praying mantis cases when I am cleaning up.

HTH,

Sandy

If you have violets and get fritillaries, you might have some cats overwintering too. I also get American coppers and have lots of sheep sorrel, so I tend to take it easy cultivating, but once I see the first flight of the ACs I will be removing some of the sheep sorrel. It does take over very quickly, but I love those little butterflies. If I do weed, I do a thorough check of the plant--and I often leave the plant in the bed, roots up, and I will leave a little of the plant just in case I didn't notice a little caterpillar.

If you want to play it safe, wait until late May or so to mulch or mulch lightly (it might offer additional protection to the chrysalides or caterpillars).

I'm starting to learn (now that I'm paying attention) to the flight period of the local butterflies, and since so many overwinter, I am going to wait to do any weeding or thatching the lawn until late May or early June when those butterflies that overwintered as cats or chrysalides will have emerged and are on the wing.

Knowing about the overwintering butterflies does add a layer of complexity to gardening.

Some beautiful moths overwinter too in their coccoons in the leaf litter usually around the bottom of the bushes.

Thank you for thinking about the overwintering butterflies and moths!