I'm not surprised. Painted Lady cats have the most varied diet of any North American butterfly. Elm is a new one on me, too.
Keep us posted :)

Congrats, bernergrrl! I've never heard of them using elm, but then they keep surprising us!

Sherry

Well, now they're looking like QMs!

Question Mark, right? Think 3rd instar now.

Definitely a question mark. The only other possibility would be one of the commas, maybe an eastern comma. They don't occur here, but in the pictures I've seen of them, they're much paler than QMs, with a lot of white. Yours shows the dark coloring, with some orange, that question marks have.

Sherry

That definitely looks like a Question Mark caterpillar.

From Dr. James Scott's CD-ROM, "The Butterflies of North America, "A Natural History and Field Guide." I recommend this for easy access to information on butterflies.

Elm is listed at end of the list of host plants.

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"Vanessa cardui Painted Lady
Hostplants herb (rarely shrub or tree) Compositae: Cirsium arvense, texanum, discolor, vulgare, occidentale, muticum, altissimum, undulatum, breweri, neomexicanum, centaureae, solstitialis, hydrophilum, scopulorum, hesperium, Cynara scolymus, Onopordum acanthium, Silybum marianum, Carduus nutans, acanthoides, crispus, Arctium lappa, minus, Lappa officinalis, Cnicus benedictus, Artemisia frigida, stelleriana, vulgaris, ludoviciana var. gnaphalodes, Calendula officinalis, Centaurea solstitialis, nigra, Achillea millefolium, Anaphalis margaritacea, Helianthus annuus, argophyllus, Helianthella, Filago arvensis (Europe), Helichrysum, Lactuca sativa, Chrysanthemum, Parthenium argentatum, Senecio maritima (?), cineraria (?), Serratula (?), Wyethia glabra, Tanacetum, Xanthium pennsylvanicum var. canadense; Boraginaceae: Amsinckia douglasiana, Borago officinalis, Cryptantha angustifolia, Echium vulgare, Nonea, Anchusa officinalis, Symphytum officinale, Lycopsis; Malvaceae: Althaea rosea, officinalis, Malva parviflora, sylvestris, neglecta, nicaeensis, moschata, Sida hederacea, Sphaeralcea ambigua, Gossypium; Chenopodiaceae: Beta vulgaris, Chenopodium album (?); Hydrophyllaceae: Eriodictyon californicum, Phacelia campanularia; Leguminosae: Glycine max, Lupinus bicolor, albifrons, formosus, perennis, arboreus, argenteus, succulentus, arcticus var. subalpinus, Medicago sativa, Phaseolus vulgaris, Pisum sativum, Trifolium; Urticaceae: Soleirolia (Helxine), Parietaria, Urtica urens, dioica ssp. gracilis (?); Labiatae: Mentha, Salvia, Stachys sieboldii; Verbenaceae: Lantana; Solanaceae: Nicotiana glauca, Petunia, Solanum tuberosum; Rosaceae: Fragaria, Prunus (a tree); Convolvulaceae: Ipomoea batatas; Plantaginaceae: Plantago lanceolata; Cruciferae: Raphanus sativus; Polygonaceae: Rumex; Umbelliferae: Eryngium; vine Cucurbitaceae: Cucumis melo; shrub Rhamnaceae: Rhamnus; tree Ulmaceae: Ulmus americana; tree Rutaceae: Citrus sinensis; the grass Zea mays (in Europe). Obviously prefers Compositae, esp. Cirsium. Sometimes a pest on Iowa soybeans (Glycine). One larva eats about 234 square cm of soybean leaves in its lifetime, all but 7 square cm in the last two larval stages (F. Poston)."

Thanks everyone; when it got to that coloring it matched up with what my memory of later instars of QMs. It's been a few years since I raised them.

That is quite a list of food for them! They should be more plentiful I would think. I never even really see them around despite being raised in the schools in those butterfly kits.

I only remember them being straight bristly black as younger instars, no white bristles, but I may have missed out on that stage. These guys have changed so much since Saturday when they appeared to be hatchlings. (Never saw the eggs).

A picture of the 2nd instar of Painted Lady looked like a dead match for the caterpillars I had, but then they moved on.

I'm excited anyway have been checking regularly for QM eggs the past couple years only to be disappointed.

We had a QMin our yard not too long, and it landed on my husband's hat without him knowing, and when I went out to take a pic, it landed on my hand. :)

In fact, I was trying to create some kind of photo tutorial about how to clean-up/weed your butterfly garden in a sensitive way, and I found the hatchlings, which just goes to show that it pays to be careful and methodical. Most people would have just cut down the Elm, and thrown into the compost bin/heap.

Thanks!

Here is a link that might be useful: Scroll down for 2nd instar pic

Oooh! Look they might be Eastern Commas! I did see an absolutely beautiful one on my wall last fall.

This would be so great!

Here is a link that might be useful: Comma caterpillars

I'm seeing something similar, with more of a black shadow over the hind wings. (Sorry, no photo available) I saw it around my Pellitory and Nettles, then around the butterfly (fruit) feeder. I saw one nectaring on White Clover...
Lots of RAs too.