|Color and Texture of Beetles|
|Beetles are invertebrates, which means that they
have no internal skeletons. A tough, yet flexible exoskeleton called the cuticle serves as
their structural support. The cuticle serves the dual purpose of skeleton and skin,
armature and protective coating. It is composed of protein and chitin, a tough, fibrous
substance related to cellulose. Layers of chitin function like natural fiberglass,
combining toughness and flexibility with the added advantage, for a flying creature, of
being extremely light.
Coloration in beetles comes either from pigmentation or optical interference or both factors in combination. Pigmentation results from the presence of melanins, producing browns and blacks; or carotenoids, producing reds, oranges, and yellows. Optical interference colors result when light reflecting and refracting through the micro-thin transparent outer layer of the cuticle interacts visually with the pigmented layer beneath. The final effect is iridescence, in some cases subtle and lustrous, in others metallic and flashy. The mechanics of optical interference produce a variable, fluctuating color, like the moire rainbows on the surface of a diffraction grating. Light wrapping the contours of the beetles body produces color shifts; a green surface graduates to a pink or magenta edge, deep greens and blues flash bronze or gold reflections. With the added dimension of textures such as ridges, ribbing, granulation, or dimpling, the play of light over the surface creates ever more nuances and variations in color. Patterning in beetles includes all variations of stripes, zig-zags, chevrons, pinstripes, freeform brushstrokes, spots, dots, blotches, and mottling.
Many of the taxonomic names which categorize beetles within their respective genera and species are almost poetic, revealing that their human namers scientific objectivity came tinged with an appreciation of the beauty of these creatures. Translated from the Latin, Euchroma means beautiful color; Chrysophora, gold bearer; Chrysochroa, with a golden surface; and Sumptuosa gema means sumptuous, costly, and gemlike.
Many beetles exhibit cryptic coloration; their color allows them to disappear into their surroundings. Given the tremendous diversity of beetle habitats, beetle camouflage includes quite a variety of colors and textures. Iridescent and metallic colors are commonest in the tropical rainforests of Southeast Asia, South America, and Australia, while in African grasslands pigment colors in red, orange, yellow, and brown predominate.
Some of the most exotic and beautiful examples of iridescence are to be found in the various genera within the family Buprestidae, the metallic wood-boring beetles. They are commonly known as jewel beetles or flying jewels, entirely appropriate names, as no other creatures so closely approximate the color and glitter of precious gems. The elytra (wing sheaths) of Amazonian buprestids are strung and worn as necklaces and ear pendants, and fashioned into headdresses by indigenous tribes in South America.
In Japan there exists a buprestid beetle shrine, the Tamamushi-no-zushi in the Horyuji temple at Nara. Built in the seventh century AD for the Empress Suiko, it contains sacred Buddhist objects embellished with nine thousand shimmering green elytra of the buprestid Chrysochroa fulgidissima set in gilded filigree. An old Japanese legend says that a specimen of Chrysochroa placed in a tansu chest will cause clothing to magically accumulate within.
Ranging in size from 1.5 to 70 mm, buprestid beetles are usually spindle-shaped, rather like an aerodynamic elongated almond with rounded head and thorax, and abdomen tapering down to a point. Resembling nothing so much as a Surrealists vision of a toothbrush, some buprestids of the genus Julodis sport bundles of setae (bristle-like structures) in vivid shades of yellow or orange, contrasting with their metallic blue or green bodies. Another buprestid genus, Sternocera, has the same overall almond shape. Their colors vary by continent with a number of Southeast Asian species being entirely metallic emerald green in color, while some Indian and Sri Lankan cousins contrast a metallic green head and thorax with deep plum red eleytra. Central African species display rich earth reds, cinnabar, golden ochre, and shiny black.
A number of ruteline scarabs of the genus Chrysina have coloration that is utterly unique among living creatures. Their colors are such that they appear to be made of polished metal. Some golden, some silver, and some two-toned, with golden thorax and silver elytra, they are highly prized by collectors. Native to Costa Rica, and rare enough to be protected species, these specimens are costly and difficult to obtain.