Blue monarch butterflies are not real. Monarch butterflies (Danaus plexippus) are known for their distinctive orange and black patterns. While monarchs do not exhibit blue coloration, the natural world is home to numerous other butterfly species that display shades of blue.
The True Colors of Monarch Butterflies
Their wings feature a vibrant orange base, intersected by prominent black veins and outlined with black borders. These black borders also contain two rows of small white spots along the edges. The wingspan of an adult monarch typically ranges from 8.9 to 10.2 centimeters.
This coloration serves as a warning signal (aposematism) to potential predators, advertising the butterfly’s toxicity. Monarchs acquire these toxins, called cardenolides, by feeding on milkweed plants during their caterpillar stage. While there can be minor variations in the intensity of the orange hue, with migratory populations sometimes displaying redder tones, blue is not a natural color for this species.
Common Blue Butterflies Often Mistaken for Monarchs
Many blue butterfly species coexist in regions where monarchs are found. The Eastern Tailed-Blue (Cupido comyntas) has a wingspan ranging from 1.9 to 3.2 centimeters. Males have iridescent blue upper wing surfaces, while females can be lighter blue to brown or charcoal. A distinguishing feature of this butterfly is the presence of one or more thin tails on each hindwing, often accompanied by small orange spots near the tails.
Another common blue species is the Summer Azure (Celastrina neglecta), which has a wingspan of 2.3 to 2.9 centimeters. Males display an iridescent blue, while females may exhibit blue with a black border or white wings with blue at the base. Unlike the Eastern Tailed-Blue, Summer Azures lack tails on their hindwings and do not have orange spots.
In tropical regions, large, iridescent Morpho butterflies are known for their bright blue. With wingspans up to 20 centimeters, these butterflies exhibit bright blue upper surfaces contrasted by drab brown undersides with eyespots. Their blue color is not due to pigment but rather how light interacts with their wing structures.
Understanding Butterfly Coloration
Butterfly coloration arises from two mechanisms: pigments and structural colors. Pigmentary colors are produced by chemical compounds within the butterfly’s scales. These pigments absorb certain wavelengths of light and reflect others, determining the color we perceive. For example, the orange of the monarch butterfly is due to ommochrome pigments.
In contrast, structural colors are not caused by pigments. Instead, they result from the intricate microscopic structures on the butterfly’s wing scales. These nanostructures scatter and interfere with light waves, selectively reflecting certain colors, such as the blues seen in many species. This phenomenon can create iridescent effects, where the color appears to change depending on the viewing angle. The blue of Morpho butterflies is an example of structural coloration.