Synonyms and other taxonomic changes
Orig. Comb: Lygaeus fasciatus Dallas, 1852
7-8 spp. (in 2 subgenera) n. of Mex. (1)(2)
Adult: overall black and orange - leathery portion of forewing with orange forward-pointing triangle anteriorly, and orange backward-pointing triangle posteriorly, separated by a black band in the middle; membranous portion of forewing black; pronotum black with orange lateral margins; freshly-molted young adults are very pale yellow, their color becoming darker and more orangish with age; adult males have a black band on the ventral side of the fourth abdominal segment; adult females have two black spots in that location
Nymph: early instars have a bright orange abdomen, developing black spots with age; later instars are more orangish-yellow; pronotum orange with black posterior margin; wingpads black, lengthening with age
Egg: oblong with three downcurved projections at tip; color initially yellow, changing to orange and then bright red before hatching
Fields and meadows containing milkweed or dogbane
yr round in CA, TX, FL, otherwise mostly in late summer and fall (BG data)
Seeds of milkweed plants. They can be reared and fed other seeds such as sunflower, watermelon, cashew, etc. Illinois.edu
Adults sometimes take nectar (and other plant juices).
Eggs are laid in milkweed seed pods or in crevices between pods. About 30 eggs are laid a day, and about 2,000 over a female's lifespan, which lasts about a month during the summer. One or more generations per year.
They overwinter as adults. They can't survive cold winters, so they migrate south in the fall. They overwinter in the southern Atlantic and Gulf coast states where they feed and breed and gradually migrate north again in the spring and summer.
In the course of feeding these bugs accumulate toxins from the milkweed, which can potentially sicken any predators foolish enough to ignore the bright colors which warn of their toxicity.
Adults of the Small Milkweed Bug
) have a red "X" marking on the forewing, and a red transverse band on the pronotum, not orange lateral margins.
Small Milkweed Bug nymphs are more red than Oncopeltus nymphs, and have two diagonal black markings on the pronotum.
Adults of the Eastern Boxelder Bug
) and the Western Boxelder Bug
) lack triangular orange patches on the forewing.
In the far south, other species of Oncopeltus
such as the Six-spotted Milkweed Bug
) have two large orange patches on the pronotum, whereas only the lateral margins of the pronotum are orange in the Large Milkweed Bug
Arnett, p. 258, fig. 20.27--mislabeled Lygaeus (1)
Rea et al., pp. 35-36 (4)
Slater, p. 71, fig. 119 (5)
Baylor College of Medicine
live adult and nymph image
- U. of Illinois at Urbana-Champaign