Margined Whites are extremely variable in wing pattern between subspecies, between sexes, and between seasonal forms. They are best identified by elimination of other species. In southern BC there are no other Pieris except P. rapae, which has a black spot in the middle of the ventral forewing that is lacking in all other BC Pieris. In central and northern BC, Margined Whites occur with Mustard Whites, which have strongly defined narrow green vein borders on the ventral hindwings in the spring form. In northern BC, Margined Whites also occur with Arctic Whites, which have strongly defined dark grey vein borders on the ventral hindwings, with the vein borders narrowing strongly towards the wing margin. In contrast, in central and northern BC, the hindwing vein borders in Margined Whites are wide and show little or no narrowing towards the wing margin, and in southern BC populations the vein borders are not sharply defined and at most narrow only weakly towards the wing margin.
Eggs are pale yellow and conical, and have 12 vertical ribs. First instar larvae are yellow when newly hatched, turning to pale green. The mature larvae of subspecies tremblayi from McBride, BC, and marginalis from Duncan, BC, are an even green without any markings. The pale lateral line that appears in the photographs of subspecies reicheli larvae from Revelstoke, BC (Eitschberger 1983) is actually a lateral band of stiff, shiny hairs rather than colour formed by pigment. Pupae have well-developed rounded apical and dorsal projections, and are pale tan to dark green with dark markings (Eitschberger 1983; CSG).
On the ventral hindwing of the nominate subspecies, P.m. marginalis Scudder, 1861, the vein borders narrow only slightly in width from wing base to outer wing margin in the spring generation. Females are commonly yellow, and the upperside of the forewing has relatively undeveloped dark pattern elements. Pieris pallida Scudder, 1861 is a synonym of nominate Pieris marginalis, being its summer form. In subspecies reicheli Eitschberger, 1983, the vein borders on the ventral hindwing are narrower towards the outer wing margin in the spring generation. Females are almost always white, rarely yellow, and have strongly developed dark pattern elements. The summer low-elevation generation of both sexes of subspecies marginalis and reicheli have, at most, only traces of ventral vein borders. P.m. reicheli is a weakly defined subspecies, with no detected electrophoretic difference from Oregon P.m. marginalis (Geiger and Shapiro 1992). In subspecies marginalis and reicheli, the dark vein borders on the dorsal forewing of females are wider near the wing apex than near the discal cell. The vein borders on the dorsal hindwing are narrower and more faded towards the outer edge of the wings. The discal cell spots, when present, usually contrast strongly with the ground colour. The dorsal cell is usually less than half-filled with dark grey scale dusting. Females are white to clear pale yellow.
Subspecies guppyi and tremblayi usually have the vein borders on the ventral hindwing equally wide from wing base to outer margin, and the vein borders are well defined in the summer generation. The forewing outer margin is relatively straight, and the hindwing is less round than in subspecies marginalis and reicheli. Females of these two northern subspecies have dark vein borders on the dorsal forewing, and usually on the dorsal hindwing, all of even width from wing base to outer margin. The discal cell spots are usually present, faded and merging into the ground colour. The dorsal cell is usually mostly filled with dark grey scale dusting. Females are white to brownish yellow. Subspecies guppyi (TL: Skagway, AK) occurs in the wet coastal forests of the Alaska panhandle, extending into BC only on the wet coastal side of the height of land on the Haines Highway and the lower end of the Tatshenshini River. The ventral hindwing vein borders are dark grey to brown grey, and the female dorsal vein borders and dusting between veins are brown grey. Subspecies tremblayi Eitschberger, 1983 (TL: Pink Mountain, BC) occurs throughout northern BC, from Bella Coola northward in the west and McBride northward in the east. The ventral hindwing vein borders are light grey to medium grey, and the female dorsal vein borders and dusting between veins are grey.
During the last glaciation, there was an ice-free refugium in the Alexandra Archipelago of the Alaska panhandle (Pielou 1991), where subspecies guppyi may have survived, with postglacial inland dispersal prevented by continued glaciation along crest of the Coast Range. There was another ice-free refugium on the Queen Charlotte Islands (Pielou 1991), where subspecies tremblayi may have survived before dispersing inland postglacially through the Nass River and Skeena River gap in the Coast Range. Alternatively tremblayi may have evolved from guppyi during postglacial colonization inland.
Pieris was one of the Muses (Pierides) who lived on Mt. Pierus, close to Mt. Olympus. Pieris was one of the five families into which Schrank divided the butterflies. Originally Schrank applied the name to all the swallowtails and whites, with the first species name being apollo (Apollo was the patron of the Muses). Latreille later separated the swallowtails and whites, applying the name Pieris to what we now call the family Pieridae (Emmet 1991). The common name "whites" is shared with Pontia and refers to the predominantly white colour of the wings.
Whites in the genus Pieris are all medium-sized white butterflies with black markings and, especially when newly emerged, with pale yellow ventral hindwings. Some females of all the species are entirely yellow. The genus Pontia includes other species of whites.
The eggs of whites are conical, with vertical ribs down the sides and numerous small horizontal ridges between the vertical ribs. The eggs are pale yellow or yellow green. Eggs are laid singly on the leaves or flowers of plants in the mustard family (Brassicaceae), both cultivated species and native mustards. Mature larvae are green and smooth-skinned with a thin coat of fine hairs. Whites hibernate as pupae, which are roughly cylindrical and smooth except for dorsal and dorsolateral ridges; the pupae are held against a stem or other vertical surface with a girdle.
In the genus Pieris, the cross-vein at the end of the forewing discal cell curves inward towards the wing base. Unlike in the genus Pontia, this vein is not surrounded by a black spot. There are dark borders to the veins on the ventral hindwing and ventral forewing apex, except in the Cabbage White and summer broods of some other species. Geiger and Scholl (1985) and Robbins and Hensen (1986) showed that Artogeia Verity, 1947, into which some authors have placed the BC species of Pieris, is a synonym of the genus Pieris.
Until recently only two species of the genus Pieris were thought to occur in BC, the introduced Cabbage White and the Holarctic Pieris napi. Instead, there are four species of Pieris in BC, and it is now clear that Pieris napi does not occur in North America (Geiger and Shapiro 1992).
Eitschberger (1983) proposed four BC species: P. rapae, P. marginalis (four subspecies), P. oleracea, and P. angelika, which are distinguished by small differences in wing pattern characteristics. The fact that Eitschberger's book was in German, its high cost, and unreasonably critical reviews of this book by Kudrna and Geiger (1985), Ferris (1989), and Shapiro (1985b) combined to make Eitschberger (1983) ignored by most North American authors. Eitschberger's revision of Pieris is substantially supported by the electrophoretic data of Geiger and Shapiro (1992), however, which has led to a grudging acceptance of parts of his work.
During the preparation of this book, we examined several series of northern Pieris collected by Norbert Kondla and CSG, and various museum specimens. CSG conducted further sampling and rearing of northern BC Pieris. Two Pieris are sympatric in various northern locaIities, from Valemont to the southern Yukon: P. oleracea and P. marginalis tremblayi. Near the Yukon border, they a rejoined by a third species, P. angelika. Eitschberger's P. marginalis guppyi is electrophoretically quite distinct from P. marginalis marginalis (Geiger and Shapiro 1992), and the wing pattern of tremblayi indicates that it is closely related to guppyi. This suggests that guppyi and tremblayi may be a separate species from
P. marginalis. We do not raise Pieris guppyi to species status, with tremblayi as a subspecies of guppyi, because the electrophoretic data are, by themselves, insufficient to separate the taxa into two species.
Margined Whites are one of the first butterflies in flight in the spring after emerging from hibernating pupae. They are bivoltine at low to mid elevations, and univoltine at high elevations (July, August). A partial third generation occurs in September near Vancouver, and possibly elsewhere at low elevations. Females oviposit on the leaves of foodplants, and larvae feed on leaves, flowers, and fruit. At room temperature, subspecies tremblayi matures from egg to pupa in 19 days, with the adult emerging about 10 days later. Some pupae of each generation go into diapause, and adults emerge the next spring. Adults of subspecies guppyi may feed "on honey-dew, which is found on the leaves and twigs of Alder bushes," and may occur in very high densities (Wright 1892b).
Margined Whites normally utilize native Brassicaceae such as Arabis and Dentaria species that grow in open forest or subalpine meadows, but cultivated Brassicaceae are used when grown in the correct habitat. Oviposition by subspecies tremblayi on Cardamine pennsylvanica (det. A. Ceska) was observed near McBride, and the larvae were reared on that plant (CSG). Subspecies guppyi near the Tatshenshini River lays eggs on annual Brassicaceae growing deep under the surface of lush subalpine meadows (CSG). Arabis species are commonly used as the larval foodplant along the Alaska Highway in northern BC (CSG). Outside BC, foodplants include Arabis glabra, Barbarea verna, Cardamine cordifolia, Dentana, Rorippa nasturtium-aquaticum, and Thlaspi arvense (Shields et al. 1970; Emmel et al. 1971; Shapiro 1976d, 198oa; Chew 1980). Subspecies guppyi and/or Arctic Whites in Sitka, AK, use garden cabbage (Wright 1892b), unless modern competition with Cabbage Whites prevents it. In captivity Margined Whites are easily reared on common watercress (Rorippa nasturtium-aquaticum).
Margined Whites occur locally throughout southern and central BC, north to Atlin. The habitat at low elevations is damp deciduous forest areas with partial shade and cool temperatures; at mid elevations, willow/alder scrub river floodplains or avalanche chutes; and at high elevations, cool, damp subalpine meadows. Their habitats are cool and moist, and usually have regularly occuring low to moderate disturbance levels that expose patches of soil to allow their short-lived (annual, biennial, or short-lived perennial) cruciferous foodplants to constantly produce new plants from seed.
Margined Whites occur from southwestern YT east to the AB Rockies, and south to CA on the coast and in the Rockies to MEX.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2021-04-13 6:21:04 PM]
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