White butterflies are common in gardens and fields across the globe, particularly in temperate regions. They belong primarily to the family Pieridae, often referred to as the “whites and yellows.” This widespread insect family includes many species that use white coloration as a major part of their visible wing pattern.
Identifying Common White Species
The most widespread and commonly observed white butterfly is the Cabbage White (Pieris rapae). This small-to-medium-sized species has a wingspan ranging from 32 to 47 millimeters. Its white coloration is marked distinctly by black or dark gray tips on the forewings.
Male Cabbage Whites typically display one black spot on each forewing, while females have two, helping distinguish the sexes. Another common relative is the Large White (Pieris brassicae), which is noticeably bigger. It features a more prominent black band at the tip of the forewings, distinguishing it from its smaller cousin.
The Checkered White (Pontia protodice) is often mistaken for the Cabbage White, though it features more intricate dark markings on the wings. These distinct patterns create a checkered or mottled appearance, especially on the underside.
The Biology of White Coloration
The white color is not simply a lack of pigment but is due to specialized chemical compounds called pterins. The pigment leucopterin is responsible for the intense white appearance of the wings in species like the Cabbage White. These pterin pigments are deposited within microscopic granules inside the scales covering the wings.
The white color plays a role in thermoregulation, the butterfly’s ability to regulate its body temperature. White scales are highly reflective, helping the insect avoid overheating by scattering solar radiation away from the body. This reflection prevents the delicate flight muscles in the thorax from reaching lethal temperatures in direct sunlight.
Conversely, darker markings, often found closer to the body, help the butterfly absorb heat necessary for flight. By adjusting the angle of their wings relative to the sun (basking behavior), the butterfly reflects solar energy onto the dark areas of the thorax. This mechanism allows the butterfly to rapidly warm up flight muscles on cooler mornings.
Feeding Habits and Agricultural Impact
The most significant agricultural impact of the common white butterfly occurs during its larval stage, known as the imported cabbageworm. The caterpillar of the Cabbage White (Pieris rapae) has a strong preference for plants in the Brassica family. This includes commercially grown crops such as cabbage, broccoli, cauliflower, and kale.
The larvae feed voraciously, creating noticeable circular holes in the leaves. In commercial settings, the damage is compounded because caterpillars often bore into the developing heads of cabbage and broccoli. Beyond direct feeding damage, their dark green excrement, known as frass, can contaminate the harvested vegetable, making it unmarketable.
While adult butterflies feed harmlessly on flower nectar, their egg-laying behavior causes economic problems. The female lays single, yellowish eggs on the underside of host plant leaves. Multiple generations can occur in a single growing season, leading to persistent challenges for gardeners and large-scale agricultural operations.