Pearl Crescent (Phyciodes tharos) (Drury, 1773)

Diagnosis: The upper surface of this small (wingspan: 21 to 34 mm) butterfly is bright orange with extensive black markings. However, it is extremely variable and there are several closely related, similar species. The Pearl Crescent is best distinguished by the orange open areas on the wings being crossed by fine black lines. The females are generally larger and darker. The hindwing underside has a dark patch on the rear margin with a silvery crescent. In the eastern U.S. and its eastern Canadian range the antennal clubs of males and most females are rounded and black and white, like those of the Tawny Crescent (P. batesii). In the Prairies, the antennal clubs are more often elongate and have the tips orange, like those of the Northern Crescent (P. cocyta), so tharos must there be identified by the more complete reticulate pattern on the wings and by the tendency for the wing margins to appear slightly scalloped.

Range: The recent separation of this species from Northern Crescent (P. cocyta) has left some confusion concerning their ranges. However, the Pearl Crescent is mainly an eastern U.S. butterfly, reaching into Canada in southern Ontario north to Manitoulin Island, with four records from Quebec in the Aylmer area, west of Ottawa, and in the southern prairie region north to Riding Mountain, Manitoba, Batoche, Saskatchewan, and southeastern Alberta.

Specimen collection data

Similar Species: The very similar Northern Crescent (P. cocyta) has large, open orange areas on the hindwing above. The Tawny Crescent (P. batesii) is darker with a more checkered pattern and the males have a pale orange band on the upperside of the forewing. Females can be confusing and are best identified by association with males from the same colony. [compare images]

Early Stages: The mature larvae are dark brown with brown spines and a yellow stripe on the sides. They feed on a variety of asters (Aster spp.), near Ottawa on Aster ciliolatus (Catling, 1997).

Abundance: This is a common butterfly in the eastern U.S., but in most of its Canadian range it is far less common than the Northern Crescent (P. cocyta).

Flight Season: In the Prairies, there are two broods, the first starting in late May but primarily in June, and the second in August. In Ontario there are small flights in May and late September, but the largest flight is the second generation, which flies in late July and early August, later than the flight of cocyta in June and early July.

Habits: These diminutive orange butterflies often swarm in open fields, freely visiting flowers and sipping mud at the edge of puddles. In Canada they prefer drier habitats than cocyta; in the Prairies they are associated with very dry sites (badlands, hilltops, etc.).

Remarks: Females of cocyta have a more complete black pattern than males and resemble males of tharos. We suspect that some reports of tharos, especially from northern and central Ontario, are actually females of cocyta. Fieldwork in Ontario by Alan Wormington has led to the possibility that two species may be confused within tharos. A form with wider, dark wing borders, a less reticulate wing pattern, and orange-tipped antennal clubs flies abundantly in southern Ontario during July, after the flight of cocyta, but before the second generation of tharos emerges. Phyciodes tharos has been known to have forms with rounded black antennal clubs and more slender, orange-tipped antennal clubs, but the suggestion that these are distinct species is new. Molecular research, and examination of material from more areas, are in progress.

© 2002. This material is reproduced with permission from The Butterflies of Canada by Ross A. Layberry, Peter W. Hall, and J. Donald Lafontaine. University of Toronto Press; 1998. Specimen photos courtesy of John T. Fowler.