A large milkweed bugs, Oncopeltus fasciatus, is a red-orange and black bug that you'll commonly find on and around milkweed plants. From a distance large milkweed bugs look a lot like box elder bugs, but they're larger and have different coloring. If you're growing a wildlife garden and plant milkweed plants for butterflies and bees you may already be very familiar with the large milkweed bug.
The coloring of this bug ins't just for show. Milkweed bugs absorb toxic compounds (cardiac glycosides) in the milkweed plant's milky sap. Birds who are dumb enough to try to eat one will probably not make the same mistake again.
Milkweed bugs feed on the seeds of milkweed plants by piercing the seed pod. They also will feed on nectar and on the plant's juices. Since they're not a much of pollinator I have to consider them a pest. Although, in areas where there are lots of unwanted milkweed plants they are a beneficial insects. They help keep down the populations of milkweeds by feeding on the seeds. Female milkweed bugs will lay eggs in and around the seed pods of milkweed plants. If you're trying to collect seeds from a milkweed plant and fail to do so because the seed pod has been damaged, it is probably a result of the milkweed bug.
I came across this mating pair of large milkweed bugs on a common milkweed (Asclepias syriaca) in the alley near my house. As you can see they are stuck together at the ends, they can remain in that position for up to 10 hours. I'm not sure who I feel bad for, the male or the female.
While I was playing bug whisperer with these milkweed bugs I came to the conclusion that they're fancy-looking roaches. For all that warning coloration they are pretty skittish but seem to be very aware of their surroundings. I will swear on a stack of Bibles that one of them charged me when I got too close the the seed pod they seemed to have laid eggs in. If you're trying to identify a red and black bug in your garden I hope these pictures will help you ID it.
Here's a video I took of a couple of large milkweed bugs. Unfortunately, when I returned with this camera they were no longer mating. You can find more of my gardening videos here. The link will open in a new window.