Introduced to southern Canada in the 1850s, Pieris rapae can be found throughout North America (2). After winter mortality P. rapae activity and abundance increase from early spring to late fall. During this time they can be found on plants from the Brassicaceae family, attracted by glucosinolates which stimulates oviposition and feeding (2). Yellow, oblong eggs are attached to the underside of leaves during spring, though the number of generations is dependent on geographic location (3). Larvae are green with a faint yellow dorsal stripe on a velvety body about 30 mm long. P. rapae larvae are considered minor pest as they feed on outer leaves and the center of members of the cabbage family (1). Fully developed P. rapae are milky white with black markings on their wings (2). They can be found a wide variety of flowers and are extremely active during daylight hours (1).
(1) Capinera, J. L. (2000, March). Common name: imported cabbageworm scientific name: Pieris rapae (Linnaeus) (Insecta: Lepidoptera: Pieridae). http://entnemdept.ufl.edu/creatures/veg/leaf/imported_cabbageworm.htm
(2) Shapiro, A. (n.d.). Pieris rapae. http://butterfly.ucdavis.edu/butterfly/Pieris/rapae
(3) Opfer, P., & McGrath, D. (n.d.). Cabbage White Butterfly. http://horticulture.oregonstate.edu/content/cabbage-white-butterfly