With the arrival of fall, we’re starting to see pumpkins, spooky yard decorations, and pumpkin spiced everything (*shudder*). Not to be left out of the festivities, one insect can be quite noticeable this time of the year—the large milkweed bug (Oncopeltus fasciatus).
If you’re wondering, we do also have a small milkweed bugs (Lygaeus kalmii), although it’s not usually as common as the ubiquitous, larger cousin. Both juveniles (nymphs) and adults of the large milkweed bug are fittingly adorned for fall. Adults reach lengths of nearly 3/4 inch long and are mostly orange with black patches on the wings and body. Going through “simple metamorphosis” (technically, they’re paurometabolous), the juveniles or nymphs look similar in body shape to adults (although smaller) and are also orange with some black. In more mature nymphs, the developing blackish wing pads are quite noticeable. When you see a group of nymphs and adults hanging out on milkweed in the fall, it’s easy to recognize that they’re all the same species.
Large milkweed bugs specialize on milkweed plants and are one of the many creatures that can be found in and around milkweed patches. When they feed, large milkweed bugs use their sucking-type mouthparts to sip fluids from plants; they’re especially fond of the developing seed pods and are often spotted on pods. While home gardeners hoping to rear monarchs might be concerned about competition, these insects generally cause little harm to plants and are more of a curiosity than a pest.
Large milkweed bugs have a very seasonal pattern in the upper Midwest. They can’t survive the winter at more northern latitudes, so they must migrate northwards each year. Here in Wisconsin, you’d be hard pressed to find large milkweed bugs in spring, but by July they’ve often arrived in low numbers. Large milkweed bugs can become quite common by late summer and early fall as it typically takes 40+ days for a new generation of adults to appear from eggs laid in our area.
In much of Wisconsin, we’re just starting to see foliage change to reds, oranges, and yellows, but as you’re out enjoying the fall weather, keep an eye out for these festive-looking insects around milkweed patches.