The Margined White belongs to the family Pieridae, which includes the Whites, Marbles, Orangetips and Sulphurs, a worldwide group of butterflies often represented abundantly. Whites often have white wings dorsally punctuated with black markings, while ventrally many species have green or brown markings, particularly on the hindwings. Pierids are mostly medium-sized butterflies which come readily to nectar sources but which also spend a large portion of their time on the wing. Because of their tendency to be constantly moving, many pierids are often difficult to photograph even though they may be very common.

All of our whites overwinter in the chrysalis stage, except for the Pine White in which the egg hibernates. Likewise, all of our species except the Pine White utilize plants of the mustard family as their larval host plants.

The systematics of several of the whites in our region have recently been revised. Our Pieris marginalis was previously included in the European species Pieris napi, which we called the Mustard White. Currently P. napi is regarded as being restricted to the old world, and our North American form has been split into three species, with P. marginalis being the only one to occur in Washington State; the others occur further north in British Columbia. The English name “Mustard White” is still applied to a North American species which does not occur here.

The Margined White occurs from the southwestern Yukon and the Rocky Mountains of Alberta, south through British Columbia, Washington and Oregon to California along the coast and along the Rocky Mountains to Mexico. The species has been reported throughout Washington State except for the central Columbia basin, Klickitat County and the San Juan Islands.

The Margined White is multiple-brooded in Washington, with the final brood hibernating as a pupa. Adults emerge early in the early spring, and have been reported on the wing throughout a long flight period from early March through mid October. Eggs are laid on a number of mustard (crucifer) food plants, including cresses and Arabis, and larvae can be reared easily on garden cabbage. Like all Pierid eggs those of P. marginalis are initially pale yellow becoming orange, spindle-shaped, attached at one pointed end, and sculptured with longitudinal grooves & ridges. Watercress is one of P. napi‘s favorite food plants, and adults can be seen hovering around and ovipositing on this aquatic plant even though surrounded by flowing water. The eggs hatch in about 5 days, and the well-camouflaged green larvae grow and mature quickly, pupating into green chrysalides which also mature quickly. The second brood adult butterflies emerge within about 30 days after the eggs were laid.

The ventral surfaces of the wings of the first (spring) brood are marked with distinct gray borders along the veins, against a white (male) or yellow (female) ground color. Subsequent broods lack these contrasting gray markings, with the ventral wings almost pure white or yellowish.

Margined Whites are common in Washington and can frequently be found along any woodland path or roadside. They often fly together with the imported Cabbage White, Pieris rapae, from which they are distinguished by P. rapae‘s sooty wingtips. Also, the Cabbage White lacks gray vein edges on the ventral hindwing, making the spring brood of P.marginalis easy to separate.

All Photos by Dave Nunnallee

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