Pruinescence , or pruinosity, is a "frosted" or dusty-looking coating on top of a surface. It may also be called a pruina (plural: ''pruinae''), from the Latin word for hoarfrost. The adjectival form is pruinose .

Entomology

In insects, a "bloom" caused by wax particles on top of an insect's

cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

covers up the underlying coloration, giving a dusty or frosted appearance. The pruinescence is commonly white to pale blue in color but can be gray, pink, purple, or red; these colors may be produced by

Tyndall scattering The Tyndall effect is light scattering by particles in a colloid or in a very fine suspension. Also known as Tyndall scattering, it is similar to Rayleigh scattering, in that the intensity of the scattered light is inversely proportional to the ...

of light. When pale in color, pruinescence often strongly reflects

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

. Pruinescence is found in many species of

Odonata Odonata is an order of flying insects that includes the dragonflies and damselflies. Members of the group first appeared during the Triassic, though members of their total group, Odonatoptera, first appeared in Late Carboniferous. The two comm ...

, particularly

damselflies Damselflies are flying insects of the suborder Zygoptera in the order Odonata. They are similar to dragonflies, which constitute the other odonatan suborder, Anisoptera, but are smaller and have slimmer bodies. Most species fold the wings along ...

of the families

Lestidae The Lestidae are a rather small family of cosmopolitan, large-sized, slender damselflies, known commonly as the spreadwings or spread-winged damselflies. Characteristics While most damselflies rest with their wings folded together, most member ...

and

Coenagrionidae The insect family Coenagrionidae is placed in the order Odonata and the suborder Zygoptera. The Zygoptera are the damselflies, which although less known than the dragonflies, are no less common. More than 1,300 species are in this family, making i ...

, where it occurs on the wings and body. Among true

dragonflies A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threa ...

it is most common on male

Libellulidae The skimmers or perchers and their relatives form the Libellulidae, the largest dragonfly family in the world. It is sometimes considered to contain the Corduliidae as the subfamily Corduliinae and the Macromiidae as the subfamily Macromiinae. Ev ...

(skimmers). In the

common whitetail The common whitetail or long-tailed skimmer (''Plathemis lydia'') is a common dragonfly across much of North America, with a striking and unusual appearance. The male's chunky white body (about 5 cm or 2 inches long), combined with the brown ...

and

blue dasher The blue dasher (''Pachydiplax longipennis'') is a dragonfly of the skimmer family. It is the only species in the genus ''Pachydiplax''. It is very common and widely distributed through North America and into the Bahamas. Although the species nam ...

dragonflies (''Plathemis lydia'' and ''Pachydiplax longipennis''), males display the pruinescence on the back of the abdomen to other males as a territorial threat. Other Odonata may use pruinescence to recognize members of their own species or to cool their bodies by reflecting radiation away.

Plants, fungi, and lichens

The term ''pruinosity'' is also applied to "blooms" on plants—for example, on the skin of

grape A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus ''Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters. The cultivation of grapes began perhaps 8,000 years ago, ...

s''‘Sangiovese’ and ‘Garganega’ are two key varieties of the Italian grapevine assortment evolution''
, M. Crespan, A. Calò, S. Giannetto, A. Sparacio, P. Storchi and A. Costacurta, Vitis 47 (2), 97–104 (2008); p. 98-99 discusses different

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...

s of ''

Vitis vinifera ''Vitis vinifera'', the common grape vine, is a species of flowering plant, native to the Mediterranean region, Central Europe, and southwestern Asia, from Morocco and Portugal north to southern Germany and east to northern Iran. There are curre ...

'' '

Catarratto Catarratto is a white Italian wine grape planted primarily in Sicily where it is the most widely planted grape. Catarratto can make full bodied wines with lemon notes.J. Robinson: ''Jancis Robinson's Wine Course'' Third Edition, p. 101. Abbevill ...

' showing varying pruinosity—and to powderings on the cap and stem of

mushroom A mushroom or toadstool is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground, on soil, or on its food source. ''Toadstool'' generally denotes one poisonous to humans. The standard for the name "mushroom" is t ...

s, which can be important for identification. An epinecral layer is "a layer of horny dead fungal hyphae with indistinct lumina in or near the cortex above the algal layer".Pruina as a Taxonomic Character of the Lichen Genus ''Dermatocarpon'', Starri Heidmarsson, The Bryologist Vol. 99, No. 3 (Autumn, 1996), pp. 315-320

/ref>

References

{{reflist Insect morphology Plant morphology