Dragonflies (infraorder Anisoptera) are insects whose vibrant appearance is a defining characteristic of wetland ecosystems. Belonging to the order Odonata, their bodies and wings showcase a diverse palette. Their coloration is deeply connected to their survival, reproductive success, and physiological function, meaning the question of “what color are dragonflies” does not have a single answer.
The Spectrum of Dragonfly Colors
Dragonflies display a wide array of colors. Many species are known for brilliant, iridescent blue and green bodies, often seen in the darner family (Aeshnidae). Species like the Blue Dasher are covered in a powdery sky-blue, while others feature deep, metallic green and bronze hues that shimmer in the sun.
A significant number of species are characterized by warmer tones, including bright yellows, rusty browns, and vivid reds. The skimmer family (Libellulidae) includes many examples of red dragonflies, such as the Red Skimmer. These colors often intensify as the insect matures. While usually transparent, the wings can also feature distinct color patches, ranging from pale yellow to black or dark red spots used for signaling.
How Dragonflies Create Color
Dragonflies achieve their color range through a combination of two mechanisms: structural and pigmentary coloration. Structural color is responsible for the most brilliant and metallic blues and greens, and it is purely a physical phenomenon. These colors are produced by microscopic physical structures, or nanostructures, on the insect’s outer layer, the cuticle.
When light hits these nanostructures, it is scattered and refracted, creating the perception of color, similar to how oil slicks create a rainbow effect. Non-iridescent blue is often caused by coherent light scattering from quasi-ordered nanostructures beneath the cuticle. This physical light interaction means the color can change slightly depending on the viewing angle, resulting in iridescence.
In contrast, pigmentary color relies on chemical compounds synthesized or consumed by the dragonfly. These pigments absorb certain wavelengths of light and reflect others, producing the resulting color. The yellows, reds, browns, and blacks on a dragonfly’s body are typically the result of these chemical pigments, such as ommochromes and melanins.
Factors Influencing Color Display
A dragonfly’s displayed color is not fixed; it can change based on internal biological stages and external environmental conditions. The age of the insect affects coloration, with freshly emerged adults, known as tenerals, often appearing pale and dull. These juveniles gradually develop their full, species-specific coloration as they mature.
Sexual dimorphism is another factor, where males and females of the same species exhibit different colors or patterns. Males often possess brighter, more conspicuous colors, such as iridescent blues or dramatic dark wing patches, for use in courtship and territorial defense. Females frequently display duller browns, olives, or pale greens, which can aid in camouflage, especially when they are vulnerable while laying eggs.
Temperature also plays a direct role in color expression and thermoregulation. Darker colors absorb more solar radiation, which can increase a dragonfly’s body temperature. Some species can adjust their coloration over a short period by moving pigment granules within their body cells. When it is cold, they darken to absorb more heat; conversely, in hot conditions, they become lighter to reflect heat and avoid overheating.
The Biological Purpose of Coloration
The coloration of dragonflies serves multiple functions related to survival and reproduction. Color patterns are fundamental for species recognition, ensuring that males and females correctly identify and mate with individuals of their own species. This is particularly important in areas where multiple similar species coexist.
Bright, conspicuous colors and dark wing patches are used in territorial display and competition among males. These visual signals warn rivals to stay away from prime breeding territory, often reducing the need for physical confrontation.
While bright colors are associated with mating, many dragonflies rely on duller browns, greens, and cryptic patterns for camouflage. This is relevant for females seeking to avoid harassment from males or for individuals attempting to hide from predators. The balance between attracting a mate and avoiding danger is a primary evolutionary driver for dragonfly colors.