Phyciodes mylitta

Edwards, 1861

Mylitta Crescent, Mylitta Crescentspot

Phyciodes mylitta, commonly known as the Mylitta Crescent or Mylitta Crescentspot, is a small native to western North America. It is an abundant, weedy that has expanded its range following the introduction of European thistle species. The is strongly associated with thistles (Cirsium, Carduus, and Silybum) as larval plants, and visit diverse flowers for nectar. It is notable for its variable wing patterns, with males showing especially variable upperside markings, and for its ability to breed continuously in warm conditions.

NW11-10 Phyciodes mylitta mylitta (3429016347) by NSG group from Lund, Sweden. Used under a CC0 license.

Phyciodes mylitta (Mylitta Crescent) by S. Rae from Scotland, UK. Used under a CC BY 2.0 license.

NW11-11 Phyciodes mylitta mylitta (3429016627) by NSG group from Lund, Sweden. Used under a CC0 license.

Pronunciation

How to pronounce Phyciodes mylitta: //faɪˈsaɪoʊdiːz mɪˈlɪtə//

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

Identification

The Mylitta Crescent can be distinguished from the similar Phyciodes pallida (Pale Crescent) by its generally brighter orange coloration and more pronounced black markings. Females are notably darker than males, which aids in sex determination. The shows considerable individual variation in upperside pattern, particularly in males. The hindwing's reddish tone and silvered crescent marking are useful field marks, especially in colder seasons when these features are accentuated.

Images

Habitat

Found in a variety of open including meadows, stream banks in forested areas, roadsides, and disturbed urban environments. Originally associated with native Cirsium in wet habitats, it has expanded into diverse disturbed habitats following the naturalization of weedy European thistle species (Cirsium, Carduus, Silybum). In summer, colonies contract to areas with persistent thistles such as Bull Thistle (Cirsium vulgare) or, on the east slope of the Sierra Nevada, Canada Thistle (C. arvense).

Distribution

Western North America. Range extends from western Canada (British Columbia, Alberta) south through the western United States to California and into Mexico. include P. m. arizonensis (Arizona), P. m. arida, P. m. mexicana (Mexico), P. m. mylitta, and P. m. thebais.

Seasonality

period varies with elevation and latitude. Near sea level: February through November. In the high country: June through October. In Canada: June until late July. In California: until fall. Often one of the last flying at high elevations, where it visits Rabbitbrush.

Diet

Larvae feed on thistle in the Cirsium, Carduus, and Silybum. feed on flower nectar from diverse sources including thistles, Yerba Santa, and Heliotrope.

Host Associations

Cirsium vulgare - larval Bull Thistle; critical summer when other thistles dry up
Cirsium arvense - larval Canada Thistle; important on east slope of Sierra Nevada
Cirsium - larval Native and naturalized ; original before European thistle introduction
Carduus - larval Naturalized European
Silybum - larval Milk thistle; naturalized European

Life Cycle

Breeds continuously in warm weather with multiple per year. Part-grown larvae overwinter and can be observed sunning themselves on mild midwinter days. Development resumes in spring. The exhibits facultative controlled by environmental cues including and temperature, typical of multivoltine butterflies in temperate regions.

Behavior

Males patrol along roadsides and frequently perch at ground level. Both sexes visit many flower for nectar. Larvae are known to sun themselves on warm winter days. The species shows strong fidelity to thistle plants and contracts to persistent thistle colonies when seasonal hosts dry up.

Ecological Role

of diverse flowering plants. Larvae function as herbivores on thistle , with potential to influence thistle . The species has benefited ecologically from the introduction of weedy European thistles, which expanded its available and plant range.

Human Relevance

Not a significant agricultural pest. The has adapted successfully to human-disturbed and urban environments. Its association with weedy thistles makes it a common sight in roadsides and degraded areas. No known cultural or economic significance beyond general appreciation and ecological monitoring value.

Similar Taxa

Phyciodes pallidaPale Crescent; similar size and pattern but generally paler orange with less pronounced black markings
Phyciodes campestrisField Crescent; similar crescent pattern but has experienced regional declines in parts of California, unlike the abundant P. mylitta

More Details

Wing Pattern Variation

Males exhibit exceptional variation in upperside wing pattern, ranging from heavily marked to nearly patternless individuals. This variation has been noted by long-term observers and complicates field identification in some cases.

Seasonal Color Plasticity

The hindwing shows seasonal phenotypic plasticity: redder in cold seasons with more strikingly silvered crescent markings, particularly in females. This appears to be a temperature-mediated developmental response.

Historical Range Expansion

Following the introduction and naturalization of European thistle (Cirsium vulgare, Carduus, Silybum), P. mylitta expanded from native wet with native Cirsium into all types of disturbed and urban habitats. This ecological flexibility has contributed to its abundance and wide distribution.