Colias philodice

Godart, [1819]

common sulphur, clouded sulphur

Colias philodice is a North commonly known as the clouded sulphur or common sulphur. It is a that produces multiple per year. are typically pale above with no orange traces, distinguishing them from the closely related orange sulphur (C. eurytheme). Females exhibit a form (alba) that can be common in some . The species is a legume-feeder whose primarily develop on alfalfa (Medicago sativa) and various clovers, making it economically significant in agricultural settings. It ranges across most of North America except for the far northern regions of Labrador, Nunavut, and northern Quebec.

Pronunciation

How to pronounce Colias philodice: /ˈko.li.æs ˌfi.ləˈdaɪ.ki/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Males have clean borders while females have dots within the border region. The display a series of four small red spots along the outer third, a trait shared with C. eurytheme but not with C. interior. Underside of male wings is yellow; female underside is yellow or greenish-. Both sexes have a doubled hindwing spot trimmed in brownish-red. Wingspan 32–54 mm. The white form (alba) in females can be distinguished from C. eurytheme alba by border pattern when normal specimens are present; some individuals cannot be separated without reference specimens. White form males are exceedingly rare.

Habitat

Open including fields, lawns, alfalfa or clover fields, meadows, and roadsides. frequently congregate at mud puddles.

Distribution

Most of North America; absent from Labrador, Nunavut, and northern Quebec. Present in Canadian provinces including Alberta, Manitoba, and Saskatchewan, and throughout the United States.

Seasonality

with multiple per year; active spring through fall. Migratory move annually.

Diet

feed on legumes (Fabaceae), primarily alfalfa (Medicago sativa), clover (Trifolium repens), red clover (Trifolium pratense), and various other Trifolium . Also recorded on deer vetch (Lotus species), white sweet clover (Melilotus albus), ground-plum (Astragalus crassicarpus), and other Astragalus species. nectar at (Asclepias), (), coneflowers (Echinacea, Rudbeckia), dandelion (Taraxacum), tall verbena (Verbena bonariensis), and numerous other flowers.

Host Associations

Medicago sativa - primary larval alfalfa
Trifolium repens - larval clover
Trifolium pratense - larval red clover
Melilotus albus - larval sweet clover
Astragalus crassicarpus - larval ground-plum
Astragalus plattensis - larval Platte River milk-vetch
Lotus species - larval deer vetch
Robinia pseudoacacia - larval black
Prunella vulgaris - larval self-heal
Vicia species - larval vetch
Glycine max - larval soybean

Life Cycle

Pale laid singly on plants; eggs turn red after a few days, then gray before hatching. are green with stripes along each side, sometimes with pink or orange bars. Young larvae exhibit . Green hangs upright by silken ; turns yellow with pink 'zipper' just before . with multiple per year. Overwinters as larva primarily in vetch at low altitudes, colonizing alfalfa as vetch senesces in May–June.

Behavior

engage in , congregating at mud puddles in swarms. Virgin females discriminate males from C. eurytheme males using scent cues. Receptive females assume a fixed position with held ventrally between . Exhibits . show facultative monophagy based on prior feeding experience—early experience on a particular can lead to behavioral and physiological specialization for that host.

Ecological Role

of diverse flowering plants through nectar-feeding. Larval on leguminous plants, with significant economic impact as a pest of alfalfa. Serves as for various and . Relative to herbivores of non-legume C3 plants, appears less affected by elevated atmospheric CO2 due to nitrogen-fixing capacity of legume .

Human Relevance

Significant agricultural pest of alfalfa; damage when are high. Subject of extensive research in , range evolution, and climate change biology. Popular with watchers and photographers. Used in educational contexts for rearing and observation.

Similar Taxa

Colias eurythemeOrange sulphur; may also be yellowish but typically shows orange traces, especially in males; males lack UV-reflective pattern present in C. philodice males; red spot pattern similar; alba forms can be difficult to distinguish without reference specimens
Colias interiorPink-edged sulphur; lacks four red spots on outer third; with different ; feeds on Vaccinium rather than legumes
Pieris rapaeCabbage ; white form alba of C. philodice may be confused with this , but differs in style and pattern details
Pontia protodiceCheckered ; white form alba of C. philodice may be confused with this , but differs in style and pattern details

More Details

UV reflectance and mate recognition

Males of C. philodice possess UV-reflective surfaces while C. eurytheme males do not; this difference is visually apparent under UV light and plays a behavioral role in courtship. Virgin females use scent to discriminate males from C. eurytheme males.

Host range evolution

have demonstrated documented shifts in preference, including of legumes such as alfalfa and Coronilla varia. This represents a well-studied example of host range expansion in .

Elevated CO2 response

Unlike of non-legume C3 plants, C. philodice are relatively buffered against effects of elevated atmospheric CO2 due to the nitrogen-fixing capacity of legume , which maintain leaf nitrogen content under elevated CO2 conditions.

Hybridization

When hybridized with the C. interior, hybrid exhibit abnormal dynamics—approximately 50% cease feeding but fail to enter diapause, subsequently starving—and show reduced utilization on legume hosts.

Blue-green caterpillar mutation

A mutation affecting color produces -green ; the origin and of this mutation has been investigated.