08/26/2026
If you have been checking your milkw**d for monarch caterpillars the past few weeks, you may have noticed some other critters feasting on the milkw**d. Several insects feed on the milkw**d plant besides monarch caterpillars. The most common ones are milkw**d bugs, milkw**d beetles, the milkw**d tussock moth caterpillars, and aphids.
The toxins in milkw**d give monarchs a bitter taste, protecting them from predators. Other insects also take advantage of this natural protection. The milkw**d tussock caterpillar, or milkw**d tiger moth, is a hairy black, white, and orange caterpillar, often seen in small groups from mid to late summer. Like the monarch caterpillars, it feeds on the leaves, often leaving them skeletonized. They generally feed on the older shoots, while monarchs prefer younger shoots, so the two species are not in competition with each other.
Milkw**d beetles are orange-red with black spots. Two of the most common types are the red milkw**d beetle and the swamp milkw**d beetle. Each has its preferred food, the red beetle preferring common milkw**d, while the swamp beetle, as its name suggests, is more often found on swamp milkw**d. They feed on the leaves, buds and flowers of the milkw**d plant.
Then there is the milkw**d bug, a true bug, which means they have specialized, piercing mouth parts. These are red and black and feed on the sap and seeds of milkw**d plants. They are often seen on other species of Asclepias, like butterfly w**d. Because they are often seen in large groups, the sight of them may cause alarm for some gardeners, but they do little damage to the plants and shouldn’t be a cause of concern.
Another insect often found on milkw**d plants is an aphid, specifically the oleander aphid which is bright yellow with black legs. Unlike the other insects feeding on milkw**d, this aphid was introduced from the Mediterranean region but is now found through much of North America. It sucks sap from the plant tissue, and if there are large colonies of them, they can stress or even kill small or new plants. They can be dislodged with a strong spray of water or by using insecticidal soap or neem oil. But keep in mind, this could also affect monarch caterpillars, so it is generally not recommended. They do have some natural predators which may also help to control the population.
The bottom line here is that all of these insects are harmless and best left alone. If you are concerned about them, plant more milkw**d so that there is enough for all of these creatures to share!
For more information and photos of these common insects, check out the University of Wisconsin Extension https://hort.extension.wisc.edu/articles/common-milkw**d-insects/ or this article from the Illinois Extension https://extension.illinois.edu/blogs/good-growing/2021-07-30-more-monarchs-what-are-those-bugs-my-milkw**d