Chrysina, or jewel scarabs (not to be confused with jewel beetles, which are a different family), is a genus of brightly colored, often metallic iridescent species of ruteline beetles. They range from the southwestern edge of the United States, through Mexico and Central America, and as far south as Colombia and Ecuador. Chrysina contains more than 120 species, includes all those formerly in the genus Plusiotis. The genus name is from Greek χρύσινος (chrysinos), "gold-coloured".

Distribution and habitat

Although the genus is wide-ranging, each species tends to be quite restricted in both habitat and distribution, with the vast majority only found in a single or two countries. Most species are from Mexico and Central America. The highest diversity is in Mexico and Panama, each being home to more than sixty species; Costa Rica, Guatemala and Honduras also have many species, whereas Belize, El Salvador and Nicaragua each only are known to house one or two species. There are only three species in South America where restricted to western Colombia and western Ecuador, and four species in the United States where restricted to highlands of Arizona, New Mexico and western Texas. They tend to be found in pine, juniper or pine-oak forests, or in cloud forests, most commonly between 1000-3000 m elevation, but there are also species found up to 3800 m or in lowlands.

Behavior

The immature stages of most species are unknown, but where known the larvae live in and feed on rotting wood, while the adult beetles feed on foliage. They are harmless to humans and not regarded as pests. The adult beetles are attracted to light during the night.

Appearance

These beetles are typically between 15-35 mm in length. The majority of species have bright shiny green upperparts, but metallic silver and gold are also common colors (species with all-silver or all-golden upperparts only occur in Central and South America), and a few can be metallic reddish. Some species combine the colors, like the green-and-silver striped C. gloriosa. They are very popular among collectors; many species are polymorphic. While their value often is quite low, only a few US$, particularly attractive specimens were reported to sell for as much as US$500 in 2007.

Metallic color mechanism

Research has shown that the elytra of Chrysina are composed of about 70 chitinous layers of exoskeleton. The different reflective indices and spacing of the layers cause light of different wavelengths to be selectively refracted through them and by them in different phases, leading to a metallic appearance, and also leads to different specimens having different colors.

Species