Swollen milkweed pods line country roads in early fall. When fully mature, the pods split and the seeds disperse courtesy of the silky parachute attached to each one.

But a close inspection of these bulging seed pods often reveals a striking black insect with bright reddish-orange markings.

Milkweed bugs are seed eaters. Adults and immatures gather on milkweed seed pods, sometimes by the dozens. These seed-eating true bugs, members of the order Hemiptera, face a dilemma: they have piercing-sucking mouthparts. They cannot chew through a seed's tough outer shell like rodents or crack seeds like birds. Instead, they pierce the seed coat with sword-like beaks and inject saliva into the seed. The saliva digests the seed's insides, and after a time, the bug sucks up the soupy contents through its tube-like beak.

Larger amounts of saliva dissolve seeds faster and more completely. That's why milkweed pods become communal dining sites. Many milkweed bugs attacking many seeds mean more food for all. This technique also permits other seed-eaters to attack larger seeds than an individual bug could handle.

The bright orange markings on milkweed bugs warn predators away. Like monarch butterfly caterpillars, which eat milkweed leaves, milkweed bugs are foul-tasting, thanks to chemicals in the milkweed plants. These chemicals protect milkweeds from most, but not all, herbivores.

Large milkweed bugs (Oncopeltus fasciatus) share another fascinating behavior with monarch butterflies -- they migrate. University of Delaware entomologist Doug Tallamy describes in his book "Bringing Nature Home" (2007, Timber Press), that large milkweed bugs migrate from their wintering grounds along the Gulf Coast to as far north as Canada.

Milkweed pods don't mature until late summer in the northern half of the continent, so milkweed bugs winter in the Gulf Coast states where milkweed seeds are available during the colder months. When summer returns, large milkweed bugs follow milkweeds as they mature from south to north. That's why we only see this species in late summer as milkweed pods mature.