Harlequin Bugs (Murgantia histrionica) are usually found on plants in the Mustard Family (Brassicaceae), and these bugs are serious pests of cabbage and related cruciferous crops like broccoli, turnips, cauliflower, and mustard. Harlequin Bugs will suck the sap of cruciferous plants, causing the plants to wilt and die, and entire crops can be lost due to their actions.
Harlequin Bugs are boldly patterned in black and orange, and their conspicuous coloration serves as a warning to potential predators like birds that they are poisonous and foul-tasting. Harlequin Bugs accumulate the glucosinolates normally found in plants in the Mustard Family. Many glucosinolates have a hot, bitter flavor, and they are what gives cruciferous vegetables like mustard or broccoli their distinctive flavors.
In normal dietary doses, glucosinolates have extremely healthful, anti-cancer properties, but highly concentrated glucosinolates (as found in Harlequin Bugs) can be inedibly bitter and toxic, especially to smaller, non-herbivorous creatures like birds. Interestingly, glucosinolates may also serve as a natural form of weed control.
This particular Harlequin Bug was crawling around on a blooming Pink Windmills or Slimleaf Plainsmustard (Schoenocrambe linearifolia).
These native, Southwestern wildflowers, as indicated by the presence of a Harlequin Bug, are members of the Mustard Family. Here in Arizona, Pink Windmills can be found blooming anytime from May to October. Their pinkish lavender flowers have 4 petals with narrowed bases, and their green leaves are linear to lanceolate in shape. Pink Windmills can grow to be up to 4 feet (1.2 m) tall, and they can be found in a variety of habitats. I discovered this one growing in the Chihuahua Pine Picnic Area in the Santa Catalina Mountains near Tucson in October of 2005.