Metallic Wood-boring Beetle

Metallic wood-boring beetle is the common name most often used in North America for the family Buprestidae — the same iridescent, bullet-shaped beetles known elsewhere as jewel beetles. The name highlights their larval life stage, when the grubs tunnel through the inner bark and sapwood of trees.

This family includes well-known genera such as Chrysobothris (flatheaded borers) and Agrilus, the genus that contains the emerald ash borer, one of the most economically significant tree pests introduced to North America in recent decades.

Adults are sun-basking, quick-flying beetles usually seen on bark or foliage, while the wood-boring larvae play a natural role in breaking down weakened, damaged, or dead trees, accelerating decomposition and nutrient cycling in forest ecosystems.

• Compact, elongated, tapering body with a hard, domed back and a coppery, bronze, green, or blue metallic sheen.
• Short antennae and strong, spade-like legs adapted for gripping bark.
• Larvae are legless, flattened, and cream-white with an enlarged, flattened segment just behind the head, giving rise to the name "flatheaded borer."
• Lookalikes: distinguished from roundheaded (longhorn beetle) borers by the flattened larval body and the D-shaped, rather than round, adult exit hole in bark.

These beetles are found wherever host trees grow, from forests and woodlots to orchards, parks, and street trees. Adults favor warm, sunlit bark surfaces and are most active on hot, sunny days in late spring through summer. Larvae remain hidden within bark and wood tissue, often concentrated on the sun-exposed side of trunks and limbs that are stressed, damaged, or declining in vigor.

Adults are strong fliers that bask on tree trunks and branches, feeding lightly on foliage, bark, or flowers, and are quick to take flight when approached. Larvae feed by tunneling winding galleries through the cambium layer just beneath the bark, disrupting the tree's ability to move water and nutrients in heavily infested wood. Because they preferentially target already-weakened or stressed trees, they function ecologically as agents of decomposition, though certain species are considered pests of orchard, ornamental, or forest trees when populations are high.

Development follows complete metamorphosis. Eggs are laid in bark crevices, and larvae bore inward to feed on the phloem and outer sapwood, passing through several instars over a period of one to two years depending on species and wood conditions. Pupation occurs within a chamber in the wood, and the emerging adult chews its way out through a flattened, D-shaped hole. Most species have one generation per year in temperate climates, overwintering as larvae inside the tree.