Milkweed Bugs

Boldly-patterned large milkweed bugs can be found in colonies feeding on the developing and maturing seed pods of milkweeds along roadsides and field edges in late summer and early fall. Large milkweed bug is an insect in the order Hemiptera, the “half wings.” The hind wings of insects in this order are uniformly membranous and used for flight; the forewings are leathery at the base and membranous only at the overlapping tips. The edges of the wings of “true bugs” cross over the middle of the back to create a distinct “X” with a triangular scutellum above it. Sucking mouthparts arise from the front of the face, folding between the legs when not in use.

Like other true bugs, large milkweed bug undergoes simple metamorphosis. Nymphs are red with black antennae and legs, but lack functional wings. Adults are black at both ends with red (older individuals) or orange (younger individuals) markings on the edges of the thorax and scutellum and a black band across the middle. Unlike true bugs in other families, the seed bugs have both simple eyes and compound eyes.

Milkweed bugs have evolved an immunity to the cardiac glycosides in milkweed plants. Their bright colors warn birds to avoid them. Milkweed bugs drop into the grass when disturbed.

Carol McFeeters Thompson is the site interpreter at Weldon Springs State Recreation Area.

By: Carol McFeeters Thompson