Buprestid beetles, commonly called jewel beetles, form a large and diverse family of insects known for their striking appearance. These beetles often display iridescent, metallic colors. With approximately 15,500 species identified across 775 genera, they are distributed globally, inhabiting various environments from forests to grasslands.
Distinctive Features
Buprestid beetles are recognizable by their flattened, elongated, and often boat-shaped bodies. Their most notable characteristic is the metallic iridescence, which gives them the “jewel beetle” moniker. This coloration is not due to pigments but rather to structural coloration, where microscopic textures in their cuticle selectively reflect specific frequencies of light, similar to how a compact disc reflects colors. This optical effect can produce a variety of metallic hues, including greens, blues, reds, coppers, and golds.
These beetles vary in size, ranging from a few millimeters long to up to 80 mm, although most species are under 20 mm in length. Their bodies can be elongated or squat and compact, often featuring large, protruding eyes and serrated antennae that may be tucked close to the body. The tough, smooth elytra, or wing covers, provide protection for the delicate wings underneath and are frequently pitted, ridged, or lumpy.
Life Cycle and Behavior
Buprestid beetles undergo a complete metamorphosis, progressing through four stages: egg, larva, pupa, and adult. The female beetle lays her eggs in bark crevices of a host plant. Once the eggs hatch, the larvae tunnel into the wood or plant tissue.
These larvae are referred to as “flatheaded borers” due to their flattened shape and their habit of tunneling into wood. As the primary feeding stage, larvae chew winding tunnels, known as galleries, within the host plant, often under the bark. These tunnels can span the entire length of a tree or stem, and larvae may remain in this stage for several years before pupating within these tunnels. Adult beetles then emerge from the host plant, often through D-shaped exit holes. Adult feeding habits vary; some species feed on foliage, pollen, or nectar, while others do not feed significantly.
Impact on Trees
Buprestid beetles, particularly their larval stage, cause damage to trees by creating winding tunnels, or galleries, underneath the bark. These tunnels disrupt the tree’s vascular system, specifically the phloem and xylem, which transport nutrients and water. This disruption can lead to girdling, effectively cutting off resources and causing tree death.
Common signs of an infestation include D-shaped exit holes on the bark. Sawdust-like frass, which is beetle excrement, may also be visible in bark crevices. Canopy dieback or thinning, where branches in the upper crown begin to die, can indicate larval activity within the tree. While many buprestid species target dead or dying wood, some are serious pests of healthy trees, such as the Emerald Ash Borer (Agrilus planipennis), which has devastated ash tree populations, and the Bronze Birch Borer (Agrilus anxius), a native insect that attacks birch species.
Management Strategies
Preventing and managing buprestid beetle infestations involves several strategies, with maintaining tree health being a primary defense. Proper watering, fertilization, and pruning help trees remain vigorous, increasing their natural resistance to attack. Early detection of infestation signs, such as D-shaped exit holes or canopy dieback, aids timely intervention.
Physical removal of infested wood involves pruning affected branches or removing infested trees to prevent further spread. For high-value trees or severe infestations, chemical treatments, such as systemic insecticides, are an option. These treatments often require professional application and adherence to guidelines. Biological controls, which involve introducing natural predators or parasites of the beetles, are also being explored and used as part of integrated pest management plans.