Species Profile: Margined White

Margined Whites range throughout most of western Washington, with scattered populations in the northeast and southeast corners of the state.  They are one of the first butterflies to appear in the Spring in Western Washington, and are common along forest roads and wooded rural areas.  Margined Whites are often mistaken for their introduced European cousin: the Cabbage White.  On May 1 of this year, I found some Margined White eggs on a native bittercress (likely Cardamine angulata) in the Mosquito Creek area northwest of Longview, WA. I brought three of the eggs home and all three hatched three days later.  Only one of the larvae survived to adulthood, and it emerged yesterday, June 7.  During another trip to Mosquito Creek on May 22, I found a 1st instar larva on the same plants where I found the eggs, and brought it home.  It is in the final (5th) instar right now and should be pupating soon.  I reared both larvae entirely on garden cabbage (young plants I purchased from a garden center).
Margined White (Pieris marginalis)
Description
Wingspan: 38 to 57 mm
Male: white above and below, sometimes with yellowish tint.  Veins usually lined with gray to greenish-gray, especially on VHW.  Spring form has more gray on dorsal wings.
Female: slightly heavier gray markings.
Egg: yellowish white.
Larva: bright green covered with tiny white and dark green speckles and faint stripes.
Pupa: greenish yellow to tan.
Similar Species
Cabbage White (Pieris rapae) almost always has one or two black spots on DFW and black FW apex, and lacks the dark wing veins on the VHW.  Some forms of Margined White lack strongly-marked VHW veins and may have faint black DFW spots similar to Cabbage Whites.  Margined Whites tend to be more common in woodlands and forest edges, while Cabbage Whites are more common in disturbed habitats.
Habitat & Biology
Habitat: woodland edges and clearings, riparian areas and forest road corridors.
Overwintering stage: pupa.
Larval host:  native crucifers, including rockcress (Arabis spp.) and bittercress (Cardamine spp.).
Adult food source:  many flowers, including mustards, dandelions, asters, daisies, cinquefoils, and salmonberry.

Flowers of plant (likely Cardamine angulata) that eggs were found on.

Leaf of plant (likely Cardamine angulata) that eggs were found on

Margined White (Pieris marginalis) egg on Angled Bittercress (Cardamine angulata)

Newly-hatched larva (L1) of Margined White (Pieris marginalis)

Late L1 (first instar) larva of Margined White

Freshly molted L2 (second instar) larva of Margined White

Late L2 (second instar) larva of Margined White

Freshly molted L3 (third instar) larva of Margined White

L4 (fourth instar) larva of Margined White (head is facing down)

L4 (fourth instar) larva of Margined White (head is on left)

L5 (fifth instar) larva of Margined White (head is on right)

Newly-formed pupa of Margined White

Pupa (4 days old) of Margined White - note the small white patch of the wing forming

Pupa (4 days old) of Margined White

Pupa (8 days old, 3 days before emergence) of Margined White

Empty pupa after emergence of adult Margined White

Newly-emerged male Margined White