The familiar sight of a yellow butterfly fluttering across a garden or meadow is common worldwide. These bright insects are often among the first butterflies people notice, prompting the simple question about what they are called. While yellow coloration is widespread across the order Lepidoptera, a few specific groups account for the vast majority of sightings. Identifying these creatures requires recognizing the distinct family they belong to and the unique chemical process that gives them their color.
The Primary Family of Yellow Butterflies
Most yellow butterflies encountered globally belong to the family Pieridae, commonly known as the Whites, Sulphurs, and Yellows. This large family contains approximately 1,100 species worldwide, and the yellow and white species are numerous and widespread. Within the Pieridae, yellow butterflies are concentrated in the subfamily Coliadinae, often referred to specifically as the Sulphurs or Yellows.
Pierid butterflies are medium to small, typically having wingspans between 36 and 75 millimeters. A defining characteristic is the source of their bright colors, which are produced by pigments derived from metabolic waste products. They exhibit a distinct flight pattern, often fluttering rapidly and erratically close to the ground. Many males also engage in “mud-puddling,” gathering on moist soil to imbibe salts and nutrients.
Identifying Common Species
The most frequently seen yellow butterflies are Sulphurs, including the Clouded Sulphur (Colias philodice) and the Orange Sulphur (Colias eurytheme). These two species are difficult to distinguish, displaying yellow to orange-yellow color with black borders along the wing margins. They are common across North America, where their caterpillars feed on legumes like clover and alfalfa.
A much larger species is the Cloudless Sulphur (Phoebis sennae), which can have a wingspan over 70 millimeters. The male is a clear yellow with virtually no markings on the upper wing surface. The female is a darker yellow and may have a thin black border and a few dark spots. This species is a strong migrator, often traveling from the southern United States into northern regions during the summer.
The Sleepy Orange (Eurema nicippe) is a smaller, bright orange-yellow butterfly often featuring wide black borders on the upper side of the wings. Its name is thought to derive from a small black marking on the forewing that resembles a closed eye. Another yellow butterfly that does not belong to the Pieridae family is the Eastern Tiger Swallowtail (Papilio glaucus), a large insect with yellow wings marked by bold, vertical black stripes.
The Biological Source of Yellow Color
The vibrant yellow coloration in Pierid butterflies is not a structural color but a pigmentary one, created by chemical compounds called pterins. These pigments are a type of pteridine, a heterocyclic compound that the butterfly synthesizes internally, typically derived from guanosine triphosphate (GTP). The specific yellow coloring comes from a pigment known as xanthopterin, which is deposited within the nanoscale granules of the wing scales.
Pterins were first studied in these butterflies, where they were initially recognized as excretory substances used for ornamentation. The storage of these compounds in the wing scales allows the butterfly to display bright yellows, oranges, and whites, with the white coloration coming from a related pterin called leucopterin. This biological mechanism is unique to the Pieridae family among the major butterfly groups, giving them their characteristic palette.