Oncopeltus unifasciatellus

Appearance

Sexually dimorphic
Male 9.7 - 10.8 mm
Female 10.8 - 12.5 mm

Naming

Slater 1964

Distribution

Northern South America

Behavior

Oncopeltus unifasciatellus occur on a milkweed species, predominantly Asclepias curassavica, the nymphs requiring the milkweed seeds to develop.

Food

Milkweed

Predators

Scelionid wasps and nymph cannibalism

Defense

Milkweed bugs have several ways to protect themselves from predators. If you get too close to a group, the individuals will scatter. When alarmed, MBs drop off the plant into the thicket of grasses at its base. They lie still on the ground for a while before resuming their eating—predators prefer to kill their own food and generally won’t bother an animal that is already “dead.”
These behavioral methods are really moot, because MBs, as their red and black aposematic (warning) coloration suggests, are poisonous due to cardiac glycosides in the milkweed they eat. Insects that make use of milkweed carbs must either produce chemicals to detoxify them or structures to sequester the toxins. MBs sequester. At the very least, eating a bunch of bad-tasting MBs will cause a predator to vomit and to develop a strong avoidance reaction to the next MB it lays eyes on (one on-line source warned readers not to let their dogs eat MBs). The MBs’ habit of feeding in the open in large groups magnifies those colors for near-sighted predators, and there’s some speculation that the equally-gregarious but non-poisonous box elder bugs are milkweed bug mimics.
Taken from:
https://uwm.edu/field-station/milkweed-bugs-large-and-small-family-lygaedidae/