That's interesting, Larry!
D. plexippus/monarchs have laid eggs on my C. laeve, and I successfully raised a batch of cats on it. The North American native Cynanchums seem to be fine for milkweed butterflies, I think it's just the foreign type swallow wort ?C. vincetoxicum? that's poisonous to them.
I'm surprised that variegated fritillaries/Euptoieta claudia use anything in the milkweed family, though. I knew they used various wild flaxes out west, which is different enough from the Passiflora incarnata and common violets they use here, but milkweed is quite a stretch!
Sherry

If the C. utahense has been documented for Monarchs specifically, I would add it to the two Cynanchums already in the Monarch hostplant FAQ topic; let me know.

MissSherry,

All Danaids individually do not have the same tolerance for toxicity even within a given species. And along the same lines, all plants do not have the same level of toxicity even within a given species. So some of even our native plants are too toxic for some of our Monarch's while they are not for others. The conditions where the individual plant grows has a lot to do with its toxicity, and the genetics of the individual bug how high its tolerance is. Monarch cats do die from too much toxicity every day out there in nature.
FWIW, Danaus affinis, chrysippus, eresimus, genutia and melanippus also all use variuos species of Cynanchum that are not found in the US. Whether any of our D. plexippus or D. gilippus could tolerate any of those species of plants I don't know. But they do tolerate at least generally three species of Cynanchum here.

No idea who recorded the record for E. clauia and so no idea how etched in stone it really is. Bogus records are common - even see them here from time to time when sightings are accepted from hobbyists by record keepers. But I can tell you as one who established many new food plant records over the years not to be too surprised when a totally unrelated plant crops up as a viable and naturally used LFP by a species no matter how big a stretch you may think it is. Have a good example for you... Hemileuca magnifica. If you look up its LFP's in most any field guide you'll only find Artemsia filifolia - Indian or Sand Sagebrush (Townsend 1893) and A. tridentata - Big Sagebrush (Stone 1988). These two were the only known LFP's for it until Aug 1990 when I added Eriogonum effusum (Beutler 1990) at the bugs type locatity in south central CO. Both Steve Stone and Andy Warren (now Dr.) were in tow to confirm, and we even took pictures of the 3rd and 4th instar larva feeding on this new plant despite being surrounded by a sea of chest high sagebrush. I collected the larva, took them home with me and reared them through to adults on the buckwheat as a second confiration. I think buckwheat (Polygonaceae) could be called quite a "stretch" from sagebrush (Asteraceae).

Larry

Larry Gene,
You're not reading what I wrote correctly pard. I documented Cynanchum utahense for Danaus gilippus ONLY and it was accepted by the lep community. I also said "Cynanchum" is documented for the other lep examples I gave (including D. plexippus) but I didn't specify a plant species for these bugs. Cynanchum angustifolium and C. laeve are the species that are documented for Danaus plexippus. Cynanchum angustifolium is also documented for D. gilippus. None excpet the C. utahense for D.gilippus are my records.
Larry

Larry, I'm not disputing or disbelieving anything you've said, I just meant by "stretch" that the milkweed family seems to me to be far removed from the regular host plants of a given species. Like variegated frits use passionvines and violets here, which are closely related on the botanical family tree, but milkweed is a bit removed.
I also am aware of differences in toxicity - new growth has much less toxicity than old growth, where the toxins become more concentrated with age, undoubtedly the reason why hatchlings do better on it. And different growing conditions do indeed make a big difference as do individuals. In general, though, there are some plants, like C. vincetoxicum, that are generally more toxic than other Cynanchums.
Sherry

That's very interesting. While at Galveston in June, I saw many Queens but nary a milkweed of any recognizable sort. I wonder whether they were using an alternate hostplant.

Jeff

Sherry,
It's just the opposite IMO. With some advanced knowledge you should question datum. That's how the new is discovered, by folks who question the old and set out to prove to themselves what the truth is. (I knew exactly what you meant by stretch BTW.)

Jeff,
FWIW, on the Mojave desert scrub the Cynanchum plants are quite scraggly snaking around right on the ground. So they are not easily noticed. In that same habitat the primary LFP for the Monarch's is Ascepias speciosa, which is easily seen from great distance. But the Queen's don't use it and instead seem to prefer Sarcostemma cynanchoides here (another "vine" type plant).

Larry

Interesting thread. To add to the scientific discussion, when we look at what hostplants butterflies use, we tend to look as humans. This plant is related to this plant ergo. I don't know precisely the behavior of Danaids but it seems that many butterflies are going on secondary chemical charactristics first and visual clues second. The limited research I have read (and it is limited, which is how I am going to get myself in trouble here)females learn leaf shapes after successful landings. Volatile odors are the primary clues. So, if a plant, no matter what the species is, has the appropriate mix she will lay. In addition, so many factors influence egg laying including, host plant quality (e.g. nitrogen and water levels), levels of secondary chemicals, location in relation to the sun or shade. Sometimes older plants are less toxic, sometimes more, sometimes younger leaves are more toxic than older or less. When I started this, I thought, plant a few plants and all will be fine. Know I understand why diversity is so important and why we have to have so many different plants in our environment. I have studied biology all my life and nothing has taught me this like raising butterflies in my own backyard.
Again neat discussion.
-Elisabeth

Ladobe, your posting did not specifically exclude the plexippus-utahense combo; thanks for the clarification.

Larry Gene - there was no reason for me to specifically exclude "your" combo; the thread was about discovering the relationship between gilippus and utahense.