sulfur butterfly

sulfur butterfly, (subfamily Coliadinae), any of a group of about 300 species of butterflies that are bright yellow or orange and have a wingspan of 35 to 60 mm (1.5 to 2.5 inches). Seasonal and sexual dimorphism in pattern and color occur in many species. The pupae are attached to a twig by a posterior spine and a girdle of silk.

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Some species have two color patterns. For example, the alfalfa butterfly (Colias eurytheme) is usually orange with black wing margins, but some females are white with black margins. The larvae are caterpillars that feed on clover and may seriously damage crops, including alfalfa and soybeans.

One of the largest species of sulfur butterfly is the cloudless sulfur (Phoebis sennae); its wingspan ranges from about 5.7 to 8.0 cm (2.2 to 3.1 inches). Males are often solid bright yellow, whereas females are yellow with black wing margins. The cloudless sulfur is found in the Americas and is especially common in the southwestern United States. Larvae feed on plants of the genus Cassia in the pea family, and adults feed on the nectar of flowers such as geraniums, cardinal flowers, and hibiscus.

 In Asia and parts of Australia, vast swarms of lemon emigrants (Catopsilia pomona) migrate with the monsoon winds. It is thought that they primarily use visual landmarks, such as rivers and valleys, to guide them. (See also How Do Butterflies Migrate.)