**Jewel Beetles** (family Buprestidae), often called **Metallic Wood-Boring Beetles**, are famous for their brilliant, iridescent colors that shimmer with metallic blues, greens, golds, and coppers. The adults are beautiful, active fliers, typically found feeding on flower pollen or leaves in sunny areas. However, their larvae are notorious for causing extensive damage, boring through the wood of trees and shrubs, particularly those that are stressed or dying. The most economically significant species is the highly destructive invasive **Emerald Ash Borer** (*Agrilus planipennis*).
Taxonomy and Classification
Jewel Beetles belong to the order Coleoptera (beetles). They undergo complete metamorphosis. The larval stage is often called a **flat-headed borer** due to its characteristic shape: a broad, flattened thorax followed by a narrower abdomen. The larvae create distinctive, meandering, frass-filled tunnels (galleries) in the cambium and xylem layers beneath the bark, which effectively girdles and kills the host tree.
Physical Description
Adult Jewel Beetles are highly variable, often elongated or bullet-shaped, 1/8 to 2 inches long.
- **Appearance (Key ID):** Hard, bright, metallic exoskeleton. They are active during the day and can be difficult to catch.
- **Larvae (Borers):** White, legless, segmented larvae with a wide, flattened segment behind the head.
- **Damage Sign:** Distinctive **D-shaped exit holes** in the bark of infested trees (often visible after the adult emerges). Swollen, lumpy areas of bark where the galleries are underneath. Sudden, severe decline, and canopy dieback of the host tree (e.g., Ash trees attacked by the Emerald Ash Borer).
Distribution and Habitat
Jewel Beetles are found globally, particularly in tropical and subtropical forests. The adult habitat is sun-exposed foliage and flowers. The larval habitat is the phloem and cambium layer of woody hosts, particularly hardwood trees like oak, ash, maple, and cherry. Their presence is often a sign of declining tree health.
Behavior and Conflict
The larvae are specialized wood consumers and are the main cause of conflict.
- **Host Selection:** Many native species are attracted only to recently dead or severely stressed trees, helping to break down wood. Invasive species, however, can aggressively attack and kill healthy trees.
- **Girdling:** The extensive and serpentine feeding galleries of the larvae disrupt the tree’s vascular system, preventing the movement of water and nutrients, which results in the death of the crown and eventually the entire tree.
- **Economic Impact:** The Emerald Ash Borer has caused the death of tens of millions of ash trees in North America, leading to billions in eradication and replacement costs.
Management and Prevention
Control is integrated pest management (IPM), with a strong focus on prevention and chemical protection.
- **Cultural:** Maintain tree health by ensuring proper watering, pruning, and fertilization to reduce stress that attracts egg-laying females.
- **Preventative Chemical Control (Key):** For high-value, healthy trees in infested areas (like Ash trees), preventative systemic insecticide trunk injections or soil drenches are highly effective but must be applied periodically by professionals.
- **Sanitation:** Remove and properly dispose of (chip, burn, or destroy) heavily infested trees and wood before the adults emerge, often during the spring/early summer.
- **Monitoring:** Use specialized purple or green sticky traps baited with pheromones to monitor the presence and population density of invasive species.
Conservation and Research
Jewel Beetles are managed as serious forest pests. Research focuses on developing specialized, highly targeted biological control agents (e.g., parasitic wasps) for invasive species and improving systemic insecticides to protect high-value urban trees.