Everything else that lives on milkweed
Monarchs are the famous tenant, not the only one. Roughly a dozen insects in North America eat milkweed and almost nothing else, and most of them wear the same orange and black warning colors.
A milkweed is not a plant with a butterfly on it. It is a small, well-defended island supporting a community of specialists that have each independently solved the same chemical problem, plus a crowd of visitors that come only for the nectar and take nothing else.
Learning to recognize them changes what a milkweed patch looks like. Most of what people reach for a spray bottle over turns out to be the point.
The specialists
These insects eat milkweed and very little else. Every one of them has evolved some tolerance of cardiac glycosides, and most advertise it in orange, red and black.
| Insect | What it does | Where you find it |
|---|---|---|
| Monarch (Danaus plexippus) | Larvae eat leaves; the famous one | Everywhere milkweed grows |
| Queen (Danaus gilippus) | Close monarch relative, larvae on the same plants | Southern states, Texas to Florida |
| Soldier (Danaus eresimus) | Third Danaus, less common | South Texas and south Florida |
| Milkweed tussock moth (Euchaetes egle) | Gregarious tufted caterpillars, can strip a plant | Eastern and central states, late summer |
| Delicate cycnia (Cycnia tenera) | Pale moth whose larvae eat milkweed and dogbane | Eastern North America |
| Large milkweed bug (Oncopeltus fasciatus) | Pierces and drinks seeds inside the pod | Nationwide, clustered on pods |
| Small milkweed bug (Lygaeus kalmii) | Seed feeder, also scavenges dead insects | Nationwide |
| Red milkweed beetle (Tetraopes tetrophthalmus) | Adults eat leaves, larvae eat roots | East of the Rockies |
| Other Tetraopes beetles | A dozen species, several tied to one milkweed | Mostly southwestern |
| Swamp milkweed leaf beetle (Labidomera clivicollis) | Rounded orange-and-black leaf chewer | Eastern and central states |
| Milkweed stem weevil (Rhyssomatus lineaticollis) | Larvae tunnel inside the stem | Eastern North America |
| Oleander aphid (Aphis nerii) | Bright yellow-orange, all female, non-native | Nationwide, and unmissable |
Why so many of them are orange and black
Stand in front of a milkweed in August and count the color schemes. The monarch, the queen, the tussock moth caterpillar, both milkweed bugs, the red milkweed beetle and the swamp milkweed leaf beetle are all some combination of orange, red and black.
That is not coincidence and it is not shared ancestry. These are beetles, bugs, moths and butterflies, lineages separated by hundreds of millions of years. Each has arrived at the same advertisement independently, because it works: a bird that learns not to eat one orange-and-black insect on a milkweed avoids all of them.
Biologists call this a Müllerian mimicry ring, where several genuinely defended species converge on a shared warning signal and reinforce each other's lesson. Every bird that learns from one member protects the rest.
The viceroy butterfly, which looks like a monarch, was for a century the textbook case of the other kind of mimicry: a harmless species cheating by copying a defended one. That turned out to be wrong. Viceroys are unpalatable in their own right, and the relationship is mutual reinforcement rather than fraud. It is a good example of a textbook fact that quietly changed.
The visitors
Far more insects come for the nectar than for the leaves. Milkweed flowers are among the richest nectar sources in the North American flora, and because the pollen is packaged into parcels that only a strong insect can carry, the flowers select for size.
- Bumble bees are the most important pollinators of most species, and the most frequently seen carrying pollinia clipped to their legs.
- Honey bees work milkweed heavily, and beekeepers near a large stand notice it in the honey.
- Large wasps, including paper wasps and thread-waisted wasps, are effective pollinators and also hunt caterpillars on the same plant.
- Sphinx moths and hummingbird moths work pale and night-scented species at dusk.
- Butterflies of many families nectar at milkweed: fritillaries, swallowtails, hairstreaks, skippers and the monarchs themselves.
- Hummingbirds take nectar from the showier species, and are too large to be caught by the flower's mechanism.
The predators
A milkweed patch is a hunting ground, and this is the part most gardeners never notice.
- Crab spiders sit motionless in the umbels, colored to match the flowers, and take bees.
- Ambush bugs do the same job with a different body plan.
- Ladybird beetles and lacewing larvae arrive within a fortnight of an aphid outbreak and are the reason spraying is counterproductive.
- Paper wasps carry off monarch caterpillars, which is difficult to watch and entirely normal.
- Tachinid flies and braconid wasps parasitize monarch larvae, laying eggs that develop inside the caterpillar.
Monarch survival from egg to adult in the wild is commonly estimated in low single-digit percentages. Almost all of that loss is predation and parasitism, not milkweed shortage. Both matter, but only one of them is something a gardener can fix.
Birds and mammals
- Goldfinches line their nests with milkweed floss, and time their late nesting partly to the availability of it. Leaving pods standing into autumn is a small gift to them.
- Orioles and black-headed grosbeaks eat overwintering monarchs in Mexico in enormous numbers, having evolved ways to handle the toxins: grosbeaks tolerate the cardenolides, orioles gut the butterflies and eat only the least toxic parts.
- Deer and rabbits mostly avoid milkweed because of the latex, though young shoots are occasionally browsed in spring.
- Mice and voles take seed from fallen pods over winter.
What this means for a garden
Almost nothing on a milkweed needs controlling. The tussock moths arrive in August, after monarchs have largely finished with the plant, and it comes back unharmed next spring. The milkweed bugs eat seed, which is a nuisance only if you are collecting it. The beetles chew leaves cosmetically. The aphids get eaten.
The only genuinely damaging things are a drainage problem, which rots the crown, and an insecticide, which removes the entire community including the one you planted for. <a href="/guides/milkweed-pests/">The pests guide has the detail</a>.
A milkweed covered in insects is a milkweed working.
Frequently asked questions
What are the orange and black bugs on my milkweed?
Most likely large or small milkweed bugs, which feed on the seeds inside the pods and do no harm to the plant. Bright yellow-orange clusters on the stems are oleander aphids instead. Both are normal and neither needs controlling.
What eats milkweed besides monarchs?
About a dozen insects in North America eat milkweed and almost nothing else: queen and soldier butterflies, the milkweed tussock moth, delicate cycnia, large and small milkweed bugs, red milkweed beetles, the swamp milkweed leaf beetle, the milkweed stem weevil and several aphids. Hundreds more species visit the flowers for nectar without eating the plant.
Why are so many milkweed insects orange and black?
They are all chemically defended by the same plant toxins, and they have independently converged on the same warning coloration. A predator that learns to avoid one of them avoids all of them, so each species benefits from the others advertising too. This is called a Müllerian mimicry ring.
Should I remove milkweed tussock moth caterpillars?
No. They are native, they arrive in late summer after monarch use is mostly over, and although a colony can strip a plant, it returns unharmed the following spring. If you need the foliage for late monarch larvae, move them to another plant rather than killing them.
References
- Agrawal, A. A. (2017). Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution. Princeton University Press. The standard general account of the milkweed and monarch relationship. View
- Malcolm, S. B. (1994). Milkweeds, monarch butterflies and the ecological significance of cardenolides. Chemoecology 5/6: 101–117. How larvae sequester cardenolides and what that buys them. View
- Kephart, S. R. (1983). The partitioning of pollinators among three species of Asclepias. Ecology 64(1): 120–133. Which insects actually move milkweed pollinia, and how they divide up. View
- Borders, B. and Lee-Mäder, E. (2014). Milkweeds: A Conservation Practitioner’s Guide. The Xerces Society for Invertebrate Conservation, Portland, Oregon. Seed production, establishment and habitat management at field scale. View
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title = {Everything else that lives on milkweed},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/guides/milkweed-community/},
note = {Accessed DATE}
}