I don't often see the small milkweed bug on milkweed. These specimens are nectaring on wild parsnip.
The long, seed-piercing proboscis is evident in this photo.
 

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.