Pontia protodice

(Boisduval & Leconte, 1830)

Checkered White, Southern Cabbage Butterfly

Pontia protodice, commonly known as the Checkered or Southern Cabbage , is a North butterfly widespread in the southern United States and northern Mexico. The exhibits pronounced in patterning, with females displaying more extensive black and gray markings than males. are highly vagile and have been documented making significant seasonal incursions northward beyond their core range. The green , known as the Southern , feeds on a diverse array of Brassicaceous plants.

Pronunciation

How to pronounce Pontia protodice: //ˈpɒnʃə proʊˈtoʊdaɪsi//

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Identification

are distinguished from similar by the checkered pattern of black and gray markings on , more extensive in females than males. The underside of the shows extensive - veining. Wingspan ranges 3.2–4.4 cm. Males - areas in a characteristically straight, rapid pattern described as 'like it's late for an important date,' differing from the more erratic flight of . Females exhibit a distinctive rejection posture when unreceptive to mating: wings fully opened with tips below horizontal, elevated 45–60 degrees, and extruded.

Habitat

Open, disturbed dry areas including desert, plains, vacant lots, railroad corridors, airports, dry grassland, and urban environments. Also occurs in sparsely wooded areas, grasslands, and meadows in prairie and parkland regions, typically where is not heavy. Absent from heavily forested areas and regions with dense cover.

Distribution

Core range in southern United States and northern Mexico. Regularly occurs northward into the central and northern U.S. and southern Canada, though are irregular and often represent seasonal rather than permanent establishment. Absent from Pacific Northwest and New England; populations east of the Appalachians have become increasingly erratic. GBIF records indicate irregular presence in Alberta, Manitoba, and Saskatchewan, Canada.

Seasonality

Most widespread and abundant from late summer through autumn. In California's Central Valley, historically abundant at low elevations in the 1970s but now rarely seen before September and October in most years. At Sierra Valley, colonizes annually from desert regions in May or June, becoming common by late summer. Overwinters locally and sporadically in limited areas, primarily as .

Diet

nectar on mustards (Brassicaceae), composites (Asteraceae), alfalfa (Medicago sativa), and a wide variety of other flowering plants including legumes. feed on , flowers, and fruit of plants, with older larvae also consuming rosettes when larger plants are senescent.

Host Associations

Arabis petiolaris - larval Brazos rockcress
Senna obtusifolia - larval sicklepod
Brassica nigra - larval black mustard
Brassica oleracea - larval broccoli, Brussels sprouts, cabbage, cauliflower
Brassica rapa - larval turnip
Descurainia pinnata - larval pinnate tansy-mustard
Descurainia sophia - larval flixweed tansy-mustard
Lepidium densiflorum - larval prairie pepperweed
Lepidium virginicum - larval Virginia pepper-grass
Raphanus sativus - larval radish
Sisymbrium altissimum - larval tumble mustard
Thlaspi arvense - larval field pennycress
Hirschfeldia incana - larval short-lived , formerly Brassica geniculata

Life Cycle

stage: orange eggs laid conspicuously near the top of plants. Larval stage: five ; mature black-dotted, bluish-green to gray with , , and sublateral stripes. Pupal stage: overwinters as ; color variable from -gray to cream; pupa lacks the typical of many pierids, attaching only at the end. stage: emerges after winter ; males typically eclipse earlier than females.

Behavior

Males - areas to locate females, assessing female age through UV reflectance patterns on worn —older females have more melanic markings and greater UV due to loss. Males prefer larger females with longer and younger females for longer copulation duration. Males transfer substantial nutrient investment (7–8% of precopulatory body mass) via during mating, with smaller males contributing proportionally more. Females actively solicit males when spermatophore contents deplete, typically 5–7 days post-mating. Females employ thermoregulatory reflectance basking, orienting the body surface toward the sun with wings held open to reflect radiation. High male-to-female ratios in early season drive female from dense colonies to colonize new .

Ecological Role

Larval on Brassicaceae; . Significant seasonal colonizer of disturbed and open . Serves as for various ; specific relationships not documented in available sources.

Human Relevance

known as Southern , a minor agricultural pest on cultivated Brassica including cabbage, broccoli, cauliflower, and turnip. are common subjects for observation and photography. Occasionally abundant in irrigated alfalfa fields where adults visit flowers. Not considered a major economic pest compared to .

Similar Taxa

Pieris rapaeSimilar size and base color; distinguished by more erratic pattern, less extensive dark markings especially in females, and presence year-round in many areas rather than late-season peak abundance.
Pontia sisymbriiSpring overlaps in western range; earlier in season (spring rather than late summer), has dark-patterned underside but with different pattern, and is more wary with difficult-to-approach perching .
Euchloe ausonidesLarge Marble has similar size and coloration; distinguished by reticulated 'marble' pattern on underside, spring period at lower elevations, and more effective when perched.

More Details

Sexual dimorphism in UV signaling

Female surfaces are partially UV reflective, with reflectance changing as females age due to loss and tattering. Males use this as a reliable cue for female age assessment, preferring less worn (more UV reflective) females.

Rejection posture confusion

The female rejection posture— spread, elevated, extruded—has been misinterpreted as a mating invitation by observers unfamiliar with the , due to superficial similarity to attraction displays in other such as Heliconius.

Historical population shifts

In California's Central Valley, this underwent marked decline from 1970s abundance at low elevations; formerly overwintered regularly on dredge tailings along the River, but now rarely persists through winter in most of its historical range.