The Cabbage White Butterfly (Pieris rapae) is a familiar insect throughout many parts of the world, recognizable by its small to medium size and distinctive white wings. These butterflies typically display black tips on their forewings, with females also featuring two black spots in the center of their forewings, while males usually have one. Often seen fluttering in gardens, agricultural fields, and open spaces, this species is widespread. While the adult butterfly itself is harmless, its larval stage, commonly known as the “imported cabbageworm,” is a known pest of cruciferous plants.
Seasonal Egg Laying
Cabbage White Butterflies are active throughout the warmer months, with egg-laying occurring across multiple generations. In temperate regions, egg-laying typically begins in early spring (March or April) and continues through summer into early fall (until September or October). The species typically produces between three to five generations annually, though favorable conditions might see more. Each generation progresses from egg to adult in approximately three to six weeks, allowing for this continuous cycle of reproduction. Female butterflies are most prolific during the first week of their adult life, during which they lay the majority of their eggs.
Factors Influencing Egg Laying
Environmental and biological factors influence the timing and intensity of egg-laying by Cabbage White Butterflies. Temperature plays a major role, as the development of eggs and caterpillars is optimal within a range of approximately 15 to 30 degrees Celsius (60-85 degrees Fahrenheit). Larval growth is hindered by temperatures below 10 degrees Celsius or above 35 degrees Celsius, with the fastest growth observed between 30 and 35 degrees Celsius.
The availability of suitable host plants also directly impacts egg-laying behavior. Cabbage White Butterflies exclusively lay their eggs on plants belonging to the mustard family, Brassicaceae. This includes common vegetables such as cabbage, broccoli, kale, and cauliflower, as well as plants like nasturtiums. The presence and health of these host plants dictate where and when females will deposit their eggs, ensuring a food source for the hatching larvae.
Where Eggs Are Laid
Cabbage White Butterfly eggs are small, approximately 1 millimeter in length. When freshly laid, they typically appear pale yellow, gradually deepening as they approach hatching. Some descriptions note them as initially white to cream-colored before turning yellowish.
The eggs possess a distinctive shape, often described as bullet-shaped, oblong, or spindle-shaped, being roughly twice as high as they are wide with a narrow base and a blunt apex. They feature prominent vertical ridges, commonly numbering around 12 to 14, along with fainter horizontal lines across their surface. Females meticulously place individual eggs, typically one by one, on the undersides of host plant leaves.