The large milkweed bug ranges east of the Rocky Mountains. They eat the seeds of milkweed plants, and occasionally suck juices from other plants, but appear to do no significant damage.

Both small and large milkweed bugs have incomplete metamorphosis. The nymphs (immatures) look like the adults (meaning they have all the same body parts), except that they do not have full wings and their color pattern is different. Black wing pads appear early in their development. Nymphs have bright orange abdomens, and usually molt 5 times. (5 nymphal instars (stages) before becoming an adult). Eggs take about 1 week to hatch and a month to become adults. Milkweed bugs are usually found in groups on milkweed plants, often on the underside of the leaves. I have seen them in conglomerations of hundreds.

The plant produces a milky white sap when a leaf is removed. These plants are large (3-4 feet high) with sprays of small white flowers in the summer. In the fall, seed pods develop which are 4 inches long and 1 1/2 inches wide. When the seeds ripen, the seed pods open up releasing the seeds which float on fluffy white parasols. Milkweed bugs can be found on seed pods piercing the wall of the pod to feed on seeds.  Milkweed bugs are one of a small group of insects that have the ability to tolerate the toxic (poisonous) compounds in the milkweed plant. They are therefore important in regulating populations of this plant.

Milkweed bugs have few predators because they concentrate in their bodies bad tasting compounds found in the sap of milkweed plants. The bugs use their bright colors to advertise their bad taste. Inexperienced birds that taste their first milkweed bug are unlikely to try to eat another orange and black insect, such as a Monarch or Viceroy butterfly.