Synonyms and other taxonomic changes
Author: Stal 1874
Adult: dark gray to black with broad orange or red band on forewing, forming an "X" shape that doesn't quite meet in the middle; head black with dull red spot on top, sometimes extending down onto face; pronotum with red transverse band, bordered anteriorly by two black spots, and posteriorly by two black semicircular lobes; membranous portion of forewing all black in eastern specimens
In western specimens, the membranous portion of the forewing is black with large white spots and white posterior margin
Nymph: abdomen all red in young nymphs, developing black spots with age; wingpads black, lengthening with age; pronotum red with two black diagonal markings
widely dist., but rare in se US, and n. Great Plains and Rocky Mtn states (BG data)
Fields, meadows containing milkweed and other flowers
Mostly: Jun-Oct, yr round in CA (BG data)
Adults suck nectar from flowers of various herbaceous plants, and also feed on milkweed seeds(?). Also reported to be scavengers and predators, especially in spring when milkweed seeds are scarce. They have been reported feeding on honey bees, monarch caterpillars and pupae, and dogbane beetles, among others. The Life of a Californian Population of the Facultative Milkweed Bug Lygaeus kalmii
"Adults mainly feed on milkweed seeds, but they often consume nectar from various flowers." Harvard Entomology
Another example of scavenging
Eggs are laid on milkweed in spring. One or more generations per year. Adults overwinter.
Adults of the Large Milkweed Bug
) have a different pattern on the leathery portion of the forewing: an orange forward-pointing triangle anteriorly, and an orange backward-pointing triangle posteriorly, separated by a black band in the middle.
Nymphs of the Large Milkweed Bug are more orange than red, and lack two diagonal black markings on the pronotum.
Adults of the Eastern Boxelder Bug
) lack a red "X" pattern on forewing, and have three longitudinal red stripes on the pronotum, not a red transverse band.
Adults of the Western Boxelder Bug
) are mostly black with very little red.
Arnett, p. 258, fig. 20.28--mislabeled Oncopeltus (2)
Slater, p. 71, fig. 120 (3)
Milne, p. 478, fig. 116 (5)
Arnett and Jacques, #57 (6)
Borror and White, plate 3 (7)
live adult images
(Bruce Marlin, Illinois)
preserved adult image
and foodplant (Virtual Exhibit on Canada's Biodiversity)