Agrilus is a genus of jewel beetles (metallic wood-boring beetles) in the family Buprestidae, order Coleoptera. It is notable for being the single largest animal genus by species count, with nearly 3,000 described species — more than any other genus in the animal kingdom. The genus was established from the Ancient Greek ἄγριλος (ágrilos), meaning "of the field," and its type species is Agrilus viridis.
Agrilus beetles are typically small to medium-sized, elongate, and often brightly metallic in coloration — greens, coppers, bronzes, and blues are common. Like other buprestids, adults are strong fliers and are often found on foliage or bark of host plants, while larvae are legless, flat-headed wood-borers that tunnel beneath bark and in the sapwood of trees and shrubs. Larval feeding creates characteristic serpentine galleries that can girdle and kill host plants.
Members of this genus feed on a wide variety of flowering plant hosts. The most infamous species is the emerald ash borer (Agrilus planipennis), a brilliant green beetle native to northeastern Asia that has become one of the most destructive invasive forest pests in North America, killing tens of millions of ash trees (Fraxinus spp.). Other economically significant pest species include Agrilus biguttatus and Agrilus auroguttatus, which attack oak trees. The genus has a cosmopolitan distribution, occurring on every continent except Antarctica.
Etymology
The name Agrilus is borrowed from Latin, which derived it from Ancient Greek Ἄγριλος (Ágrilos) or ἄγριλος (ágrilos). The Greek word combines ἀγρός (agrós, "field") with the nominal suffix -ιλος (-ilos), roughly meaning "of the field" or "dwelling in the fields."
Distribution
Agrilus has a cosmopolitan distribution, occurring on all continents except Antarctica. The genus is most diverse in tropical and subtropical regions. The emerald ash borer (Agrilus planipennis) is native to temperate northeastern Asia (Russia, Mongolia, northern China, Japan, and Korea) but has become a highly destructive invasive species in North America and is spreading westward across European Russia toward the European Union.
Ecology
Agrilus species are wood-boring beetles whose larvae feed beneath the bark of trees and shrubs, excavating characteristic serpentine galleries in the phloem, cambium, and outer xylem. Adults feed on foliage. Larval galleries disrupt the transport of water and nutrients, and heavy infestation can girdle and kill host trees.
Individual species feed on a wide variety of flowering plant hosts. The emerald ash borer (A. planipennis) preferentially attacks ash trees (Fraxinus spp.) — in its introduced North American range, nearly all native ash species are susceptible, and without control measures all ash trees in an infested area are expected to die within 10 years. Other notable pest species include A. biguttatus and A. auroguttatus on oaks. In their native ranges, Agrilus species are typically held in check by resistant host trees, predators, and parasitoid wasps, and population densities rarely reach lethal levels.
Taxonomy Notes
Agrilus holds the distinction of being the single largest genus in the animal kingdom by number of described species — nearly 3,000. It belongs to family Buprestidae (jewel beetles or metallic wood-boring beetles), subfamily Agrilinae, tribe Agrilini. The type species of the genus is Agrilus viridis. Five fossil taxa have also been described from the genus, including specimens from Mexican amber dating to the Miocene.
Conservation
The emerald ash borer (Agrilus planipennis) is one of the most ecologically and economically destructive invasive forest insects. Since its accidental introduction to North America (first detected in 2002 near Detroit, Michigan), it has killed tens of millions of ash trees across the United States and Canada. Quarantine efforts by the USDA were ended in 2020 due to ineffectiveness, and management has shifted to biological control using parasitoid wasps from the beetle's native range, along with insecticide treatments and tree diversification. In Europe, populations spreading westward from Moscow are expected to reach central Europe by 2031–2036. Conservation concern also extends to host tree species: several North American ash species face severe population decline due to the borer.
