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Friday, July 1, 2016

Summer Sulphurs

Orange Sulphur, Colias eurytheme, on Indian Blanket

The family of butterflies known as Pieridae includes the whites and sulphurs, our most conspicuous and abundant butterfly species. They easily draw the attention of even the most casual observer as they flit about our gardens, fields, and open habitats in summer.  Sulphurs are usually some shade of yellow, orange, or white, and avidly visit flowers.  Their uppersides often feature black borders or patterns and while they usually perch closed, these patterns can sometimes be seen faintly through the wing or glimpsed in flight. The most widespread sulphurs in our area include the Orange Sulphur (Colias eurytheme), Southern Dogface (Zerene cesonia), Little Yellow (Pyrisitia lisa), and Dainty Sulphur (Nathalis iole).  

Orange Sulphur, Colias eurytheme
White Female Orange Sulphur

Found throughout most of North America, the coloration of the Orange Sulphur can be quite variable, but the typical male has a yellow upperside with orange overlay, yellow veins, a wide black border, and a dark black cell spot.  Females can be yellow or white with an irregular black border surrounding several light spots.  Both sexes have a silver spot surrounded by two concentric dark rings and a spot above it on the underside of the hindwing. With a wingspan of about 1.5 to almost 3 inches, males patrol around for receptive females, who lay eggs singly on the leaf tops of host plants in the pea family, such as alfalfa and clovers.  Orange Sulphurs have 4 to 5 broods from March to November, and overwinter in the chrysalid form.

Southern Dogface, Zerene cesonia

The Southern Dogface is easily identified by both sexes having the shape of a yellow dog’s head surrounded by black on the upperside of their forewings, with the black and white ‘eye’ not touching the black border.  The underside of the hindwing in summer is pale to bright yellow, becoming tinged with pink markings in the fall.  With a wingspan of 2 to 3 inches, the males seek out females who lay eggs on the undersides of terminal leaves of host plants such as alfalfa, clovers, and indigo.  Three broods are produced almost year round, with adults overwintering in reproductive arrest during the coldest months.

Little Yellow, Pyrisitia lisa

As their name suggests, Little Yellow butterflies are on the small side with a wingspan of 1 to 2 inches.  The upperside of the male has a yellow forewing with a wide black tip or apex and a hindwing with a black border. While the female is usually yellow and sometimes white with black borders, both sexes usually have two tiny black dots at the base of the hindwing underside.  Four to five broods occur in the south, and females lay eggs singly on midveins or between leaflets of partridge pea, wild sensitive plants, and sennas.

Dainty Sulphur, Nathalis iole

A mating pair of Dainty Sulphur in winter form

Our smallest sulphur, the Dainty Sulphur, has a wingspan of ¾ to slightly over 1 inch, and is identified by a yellow upperside with black markings that are more extensive on the female.  The underside of the forewing has an orange or yellow patch near the base with a few strong black spots closer to the outer wing edge.  In summer, the hindwing underside is pale yellow, and turns to dusty green in winter.  Both males and females tend to fly low, rest with their wings closed and held perpendicular to sun’s rays to gather warmth, and overwinter in adult form.  Flying year round, the females lay single eggs on sneezeweed, dogweed, and other asters.
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