|scientific name Colias gigantea |
common name Giant Sulphur
Fens, bogs and wet meadows.
One brood annually, with peak flight activity from late June to late July.
Most similar to the Pink-edged Sulphur (C. interior), but gigantea is larger (forewing length 26 - 32 mm, compared to 22 - 27 mm), with a larger discal spot and often with a more pronounced satellite spot. The shape of the forewing is also more rounded. Boreal region populations are subspecies mayi, while those from the Crowsnest Pass region southward are slightly smaller and are considered supspecies harroweri (Bird et al. 1995).
The immature stages are undescribed. It is believed that larvae overwinter (Bird et al. 1995). The wet, shrubby areas inhabited by this species means it is not often observed, but road allowances through fens and bogs with regenerating willows are good places to look for this insect.
Not of concern.
The larvae feed on willows (Layberry et al. 1998). There are no published reports of adult feeding behaviour.
Alaska south to northern Ontario, southern Manitoba, and northwestern Wyoming (Opler 1999).
Joe Belicek (2014-04-08)
Colias gigantea mayi F. & R. Chermock, 1940
The easiest way to see Northern Giant Sulphur in central Alberta is to drive to Redwater area, approx. 52 km NE of Edmonton (Hwy. 28A, 43 min. from Edmonton). The town of Redwater is surrounded by wide, flat expanses of farming country, interconnected by several secondary rural roads. Shoulders of these roads are in many places bordered by willow shrubs, growing to 7-8 ft., or even higher. More willows usually grow in the surrounding fens. If you come in mid June-July, as you drive slowly on the secondary, unpaved road, watch for yellow butterflies. Chances are that you will spot patrolling males of Northern Giant Sulphur in no time. The males are looking for females, using the linear road as a guide. Most of these roads are several ft. higher than the surrounding country side, built on a gravel bed. It is likely that this patrolling habit of males is similar to hill topping.
(a) Immature stages. Females lay the typical, spindle shaped, Colias type eggs singly, sometimes in pairs, on the upper surface of the willow leaf. Initially, the yellowish-white colour eggs turns intense pink as the egg develop. The larva is leafy green in colour, with two wider white, and two thin yellowish lateral lines. The body is covered with many, short, black setae, giving it a fuzzy appearance. The pupa is initially leafy green, with yellowish lateral lines and a prominent ochreous vita on the sides of the hood. The pupa is attached to the stem by the caudal silken patch and two strands of dorsal silk girdle.
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