Metalic Wood Boring Beetle
Chrysobothris
Image taken in Phoenix, Maricopa Co., Arizona. June 29, 2005.
Dying branches of trees like this one from a blue palo verde, Parkinsonia florida, are soon found by adult metalic wood boring beetles, family buprestidae. Branches may be broken by storms or scorched by fire. Eggs layed beneath the bark hatch into grubs that bore through the branch leaving a flattened, oval-shaped gallery - which lends another common name: Flat-headed Wood Boring Beetle. Several males were actively patroling the length of this recently fallen branch facing each other in mock battles. Chrysobothris have large eyes providing acute vision and a very wary nature. These beetles are able to fly with great agility, quickly folding and unfolding their wings beneath the elytra (hard wing covers).
Once within a branch the beetle larvae tunnel beneath the outer bark, focusing their attention on the nutritious phloem. This puts them several millimeters or more below the surface. A safe place it would seem, but there are also parasitic wasps that arrive on the scene of dead/dying branches that can drill down through the wood with their ovipositor and lay their own egg into the growing larva. The image below shows an ichneumonid wasp searching and then drilling down. The drill shaft is a very fine structure and is normally protected within a sheath. The shaft can be seen in the lower image.
This beetle belongs to the genus Chrysobothris, which has at least 134 species in North America according to Arnett et. al (2002)!
