The appearance of a flying insect patterned in black and red immediately draws attention. This striking color combination is known as aposematism, a biological advertisement used by various insects to warn potential predators they are unpalatable or toxic. The contrast of red or orange against black is highly memorable, signaling to birds or other insectivores that the prey is not worth the effort or the resulting bad taste. Many different species across multiple insect orders have independently evolved this warning coloration, making identification complex. Discerning the specific group requires closer attention to physical features, especially wing structure and body shape.
Identification: Red and Black Beetles
The insects most commonly recognized for their hard shell and rounded bodies belong to the order Coleoptera, or beetles. A defining characteristic of this group is the hardened forewings, known as elytra, which meet in a straight line down the center of the back and protect the delicate flying wings beneath. Lady beetles, often called ladybugs, are a prime example, with many species displaying a black-spotted red or orange dome-shaped body. The Asian Lady Beetle, for instance, exhibits a wide range of color variations, including forms that are bright red or orange with black spots, or even black with red spots.
Another common type is the Common Red Soldier Beetle, a slender beetle with a soft body, measuring about half an inch long. This species is reddish-orange, but its legs are black at the ends, and its wing cases have distinct black tips. Soldier beetles are often seen moving slowly over flower heads during the summer. They are sometimes confused with the Red-headed Cardinal Beetle, which has a completely red head and wing cases contrasting with its black legs and antennae.
Identification: True Bugs and Other Flyers
The second major group of red and black flyers are the True Bugs, classified in the order Hemiptera. True bugs are structurally distinct because they possess piercing-sucking mouthparts, unlike the chewing mouthparts of most beetles. Their wings are also different; the forewings, called hemelytra, are partially hardened near the base but membranous toward the tips. The Boxelder Bug is perhaps the most common nuisance species, identified by its flat, elongated, black body featuring thin, reddish-orange lines bordering the wings and three red lines behind the head.
Another prominent example is the Large Milkweed Bug, a slender insect approximately half an inch long. It has a black head and two large, black diamond shapes set against a reddish-orange background on its wings. The Milkweed Assassin Bug is a different type of true bug and a beneficial predator. It features a slender body, a pointed head, and a mostly red or orange coloration with black markings.
Beyond the true bugs, some moths also employ this warning coloration, such as the Cinnabar Moth. This moth has black forewings marked with bright red stripes and spots. The caterpillars of this moth feed on the toxic ragwort plant, absorbing the toxins that are then carried into adulthood, making the flyers distasteful to predators.
Habitat, Diet, and Toxicity
The ecological roles of these red and black flyers vary significantly, from beneficial predators to plant-feeding pests. Lady beetles and soldier beetles are considered helpful, as the adults and larvae of both groups consume soft-bodied pests like aphids. Soldier beetles also eat pollen and nectar. Milkweed bugs are herbivores that specifically feed on the seeds of milkweed plants, often gathering in large numbers on the seed pods. The Boxelder Bug feeds on the sap from the seeds and leaves of boxelder, maple, and ash trees.
Many of these red and black insects are considered nuisance pests when they seek shelter in homes during the cooler months. Boxelder Bugs, for instance, congregate on the sunny sides of homes in the fall before crawling into small crevices to overwinter. While the warning colors suggest danger, most common red and black flyers are not venomous to humans. Boxelder bugs and Lady beetles do not bite, but they can release a foul odor and a fluid that stains fabrics if crushed. The exception is the Assassin Bug, which, while beneficial in the garden, can inflict a painful defensive bite if handled.