Large milkweed bug

Definition

A medium-sized seed bug (Hemiptera: Lygaeidae: Oncopeltus fasciatus) native to North and Central America, characterized by bold orange-red and black aposematic coloration. Adults and nymphs feed on milkweed (Asclepias) seeds and sap, sequestering cardenolide toxins for defense. The species exhibits geographic variation in wing length and life history traits across its range from southern Canada to Costa Rica, making it a model organism for studying local adaptation, migration, and physiological ecology in true bugs.

Etymology

From 'large' (distinguishing it from the smaller milkweed bug Lygaeus kalmii) + 'milkweed' (host plant genus Asclepias) + 'bug' (Hemiptera).

Example

Large milkweed bugs form dense aggregations on milkweed pods in late summer; their bright warning coloration advertises unpalatability to predators that have learned to avoid cardenolide-laden prey.

Synonyms

• Oncopeltus fasciatus

Related Terms

• milkweed
• aposematic coloration
• cardenolide
• seed bug
• Lygaeidae
• Hemiptera
• local adaptation
• migratory polymorphism
• true bug

Usage Notes

Distinguished from the small milkweed bug (Lygaeus kalmii) by larger size, broader black bands on the pronotum, and more extensive orange coloration. Frequently used in laboratory studies of insect physiology, reproduction, and photoperiodism due to ease of rearing on sunflower seeds. Not a pest of cultivated crops; beneficial as a milkweed specialist that helps regulate host plant populations.