Jewel beetles, members of the family Buprestidae, are easily recognized by their striking, often iridescent, metallic coloration. This large family, encompassing over 15,500 named species, is found globally, with the majority residing in tropical and subtropical regions. The feeding habits of these beetles vary significantly throughout their life cycle, moving from a deeply internalized, wood-focused diet as larvae to a more external, plant-surface diet as adults. Understanding the specific food sources consumed by each life stage is key to appreciating their role in the ecosystem and their potential impact on horticulture and forestry.
The Wood-Boring Larvae: Primary Diet
The larval stage of the jewel beetle, often referred to as a flat-head borer, is characterized by its internal feeding within plant tissues. These larvae primarily consume the inner layers of wood, specifically the sapwood, phloem, and cambium, of host plants, which can include trees, shrubs, and even grasses. In some species, the larvae also bore into plant roots or stems, while a few specialized types are leaf miners or gall-makers.
The material consumed is generally the wood or bark of dead, decaying, or stressed trees, making many species important agents in the natural decomposition cycle. The larvae burrow as they feed, creating characteristic winding tunnels or galleries beneath the bark. The duration of this wood-boring stage is extensive, lasting from several months to multiple years, depending on the species and environmental conditions.
However, a small number of species, like the Emerald Ash Borer (Agrilus planipennis), target and successfully infest otherwise healthy trees. Regardless of the tree’s health, the larval diet is centered on the nutrient-rich tissues found beneath the outer bark layer. This sustained consumption fuels the larva’s development until it is ready to pupate and emerge as an adult.
Adult Feeding Habits
Adult jewel beetles engage in external feeding that is primarily focused on energy acquisition for reproduction and flight. The adult diet consists of soft plant materials like nectar, pollen, and the foliage of host plants. Nectar and pollen provide the necessary sugars and proteins to sustain their active, often diurnal, lifestyle.
Foliage consumption, which involves feeding on the leaves of various plants, trees, and shrubs, is generally less destructive than the larval boring. Adult feeding is a means of maturation feeding, ensuring the beetles have sufficient energy reserves for mating and egg production. While some species show a preference for specific plant families, their diet is broad enough that adult feeding rarely results in significant plant damage.
Adult beetles of certain pest species, such as the Emerald Ash Borer, feed on the edges of ash tree leaves, causing minor, characteristic notches. The adult life span is relatively short, often ranging from a few days to a few weeks, which limits the total amount of plant material they consume. Their feeding supports this brief, final stage of their life cycle.
Economic and Ecological Significance of Their Feeding
The feeding habits of jewel beetles result in both beneficial ecological roles and significant economic impacts. The vast majority of species, whose larvae target dead or dying wood, contribute positively to forest ecosystems by breaking down woody debris. This wood consumption accelerates the nutrient cycling process, returning organic matter to the soil much faster than natural decay alone.
The economic significance arises from a small but notable group of species that attack commercially important healthy trees, leading to serious pest status. Larval feeding on the phloem and cambium layers of a living tree disrupts the flow of water and nutrients, effectively girdling the tree. This destruction of the tree’s vascular system, rather than the consumption of wood mass, is what causes the death of the host.
A prime example is the Emerald Ash Borer, whose larvae tunnel through the inner bark of ash trees, causing millions of tree deaths across North America. The impact of this larval boring is the destruction of the tree’s structural integrity and its ability to transport resources. The consequences of their feeding include loss of forest canopy, high costs for tree removal, and the disruption of urban and forest ecosystems.