White-margined Burrower Bugs (Sehirus cinctus) are true bugs, members of the order Hemiptera. The red and black bugs in this photograph are immature nymphs and have molted once. Their coloring serves as a warning to would-be predators that they are at the very least distasteful, and possibly poisonous. Adult White-margined Burrower Bugs are roughly ¼” long, and black with a white margin (not visible in photo) along the edges of their forewings.
These bugs feed on the seeds of plants in the mint and nettle families. Being true bugs, they feed not by chewing but by piercing seeds with a sharp beak, injecting digestive enzymes, and then sucking in the partially digested food.
White-margined Burrower Bugs are fairly unusual for non-social insects in that the mothers provide care and provisions for their young, much like social insects such as ants, paper wasps and honeybees. The adults dig shallow burrows into which they place a supply of seeds and lay between 120 and 150 eggs next to the seeds. They guard their eggs and brood and bring more seeds as needed for 1-3 days after the eggs hatch. At this point, the young bugs can forage for themselves.
Adults dig down into the leaf litter in late fall, where they overwinter and emerge next spring ready to mate. If you see a large cluster of White-margined Burrowers Beetles, do not be alarmed, as they do not bite nor are they interested in eating anything but species of mint and nettle.