Large Milkweed Bug

Oncopeltus fasciatus — the large milkweed bug — is one of about 4,000 species in family Lygaeidae and a flagship species of milkweed-community ecology in temperate North America. Adults are 12-18 mm long with bright red-and-black aposematic (warning) coloration. The species feeds exclusively on milkweed (Asclepias) seeds and stems, using stylet mouthparts to pierce seeds and consume the developing endosperm. Like monarch butterflies, milkweed beetles, and several other species in the milkweed-associated insect community, milkweed bugs sequester the milkweed's toxic cardenolides (cardiac glycosides) into their own tissues — making the bugs themselves toxic to bird predators. The shared red-and-black warning coloration across multiple unrelated milkweed-feeding species is a textbook example of Müllerian mimicry: each species reinforces the predator-learning of the warning signal. Oncopeltus is one of the most-used model organisms in invertebrate developmental biology, alongside Drosophila melanogaster and Tribolium castaneum. The species' large eggs, transparent embryo, ease of laboratory rearing, and basal hemipteran phylogenetic position have made her a flagship for studies of insect segmentation, appendage development, and the evolution of the hemipteran feeding apparatus.