Skip to main content
Milkweed bug

Q:  What it the black and red insect on my milkweed plant?

A:  Thanks for bringing in a sample of the insect as there are two very similar looking.  One is the Milkweed assassin bug and the other, the Giant Milkweed bug, Oncopeltus fasciatus.  Yours was the Giant Milkweed bug which feeds in milkweed plants, preferentially the flower buds and seed pods, which are rich in nutrients. Oncopeltus fasicatus lives out its life on milkweed plants. Mating, egg-laying, development of larvae, and courtship all take place on milkweed plants. The primary food is milkweed seed, while the insects also feed on milkweed plant juices. The milkweed diet makes the bugs unpalatable and they tell predators to stay away with their combination of red and black coloring.  The species ranges from Ontario to South America, including the West Indies.