Pruinescence UK: /ˌpruːᵻˈnɛsns/ US: /ˌpruəˈnɛs(ə)ns/ [1], or pruinosity, is a "bloom" caused by pigment on top of an insect's cuticle that covers up the underlying coloration, giving a dusty or frosted appearance. The pruinescence is commonly white to pale blue in color, but can also be gray, pink, purple, or red; these colors may be produced by Tyndall scattering of light. When pale in color, pruinescence often strongly reflects ultraviolet.[2]
The adjectival form is pruinose.
Pruinescence is found in many species of Odonata, particularly damselflies of the families Lestidae and Coenagrionidae, where it occurs on the wings and body. Among true dragonflies it is most common on male Libellulidae (skimmers).[2]
In the Common Whitetail and Blue Dasher dragonflies (Plathemis lydia and Pachydiplax longipennis), males display the pruinescence on the back of the abdomen to other males as a territorial threat.[3] Other Odonata may use pruinescence to recognize members of their own species or to cool their bodies by reflecting radiation away.[2]
The term pruinosity is also applied for "blooms" on plants, for example on the skin of grapes.[4]