The butterfly Pieris brassicae, commonly known as the “large white” or “cabbage white,” is a widely recognized species across its native geographical range. It is a common sight in various open environments.
Identification and Life Cycle
Adult Pieris brassicae butterflies typically have a wingspan of 55 to 70 millimeters. Their wings are predominantly creamy white, with forewings distinctly tipped in black. Female butterflies have two prominent black spots on their forewings, along with a black smear beneath the lower spot, and a larger black tip than males. Males generally lack these two distinct black spots. This helps distinguish them from the smaller Pieris rapae, which has a wingspan of 32 to 47 millimeters and typically displays a single spot on the forewing for males and two for females.
The large white butterfly’s life cycle progresses through four stages: egg, larva, pupa, and adult. Females lay clusters of yellow, skittle-shaped eggs, often on the undersides of host plant leaves. These hatch into caterpillars, which are typically about 45 millimeters long when fully grown. The larvae are olive-green with a yellow dorsal line, marked by black spots and squares, and covered in fine, hair-bearing tubercles. After feeding, the larvae transform into a pupa, or chrysalis, which can be pale green or greyish-white, dotted with black and yellow markings, and features a flattened ventral surface with lateral ridges.
Habitat and Diet
Pieris brassicae is distributed across Europe, North Africa, and Asia. While primarily found in these native areas, occasional sightings have been reported in New Zealand and parts of New England. This butterfly thrives in open environments, including meadows, fields, gardens, and agricultural lands.
The large white butterfly larvae primarily feed on plants belonging to the Cabbage family (Brassicaceae). Common host plants include cultivated varieties such as cabbage, broccoli, cauliflower, and kale, which explains the butterfly’s common name. The caterpillars also consume wild members of this family, including garlic mustard, wild cabbage, charlock, and hedge mustard.
Impact on Gardens and Control Methods
The large white butterfly is a significant pest in gardens and agriculture. Its caterpillars consume substantial leaf tissue from host plants, leading to severe damage, defoliation, and crop destruction.
Managing Pieris brassicae populations involves several strategies to protect plants.
Physical Controls
Physical controls include covering susceptible crops with fine netting to prevent egg-laying. Manually inspecting plants and removing eggs or caterpillars can also reduce damage, particularly in smaller gardens.
Biological Controls
Biological control methods leverage natural processes. Encouraging natural predators, including bird species like sparrows, goldfinches, and skylarks, can help reduce caterpillar populations. Parasitic wasps, such as Cotesia rubecula, are natural enemies that lay their eggs inside caterpillars, leading to the host’s demise. Additionally, microbial insecticides containing Bacillus thuringiensis (Bt) produce toxins harmful to caterpillars when ingested, and are generally safe for other organisms.