Druon ignotum

Agamic generation galls can be distinguished by their clustered arrangement along leaf veins, woolly hair covering, and location on the underside of white oak leaves. The color change of the woolly covering from cream/pink to brown over winter provides a seasonal diagnostic cue. Sexual generation galls are cryptic and require dissection of buds to detect. Druon ignotum is distinguished from other oak gall wasps by its specific association with white oaks (Quercus sect. Quercus) and the particular morphology of its agamic galls.

Found in forests and woodlands where white oaks (Quercus alba and related species) occur. Host trees include bur oak, swamp white oak, overcup oak, and post oak.

Central and eastern North America. Documented from USA: Massachusetts, Connecticut, Illinois, Minnesota, Nebraska; Canada: Alberta, Manitoba, Ontario.

Agamic females emerge from overwintered galls early in spring. Sexual adults emerge later, with timing dependent on bud development. The two generations per year result in spring activity for the sexual generation and summer-to-fall development of the agamic generation.

• Quercus macrocarpa - gall inductionbur oak; agamic generation
• Quercus bicolor - gall inductionswamp white oak; agamic generation
• Quercus lyrata - gall inductionovercup oak; agamic generation
• Quercus stellata - gall inductionpost oak; agamic generation

Heterogonic life cycle with two alternating generations per year. The agamic (parthenogenetic) generation produces galls on leaf undersides; females emerge in spring and oviposit in oak buds. This induces sexual generation galls within buds and young shoots. Sexual adults of both sexes emerge, mate, and mated females oviposit on leaf undersides to induce the next agamic generation.

Females of the agamic generation exhibit precise host-finding behavior, locating oak buds for oviposition after emergence from overwintered galls. Mated females of the sexual generation target the underside of oak leaves for oviposition.

Induces structurally distinct galls on white oaks, creating microhabitats that may be utilized by other organisms. The woolly agamic galls may provide shelter for inquilines or parasitoids, though specific associates are not documented.

No documented economic or medical significance. The galls cause minimal damage to host trees and are primarily of interest to entomologists and naturalists studying gall wasp biology.

• Other Druon speciesSimilar gall morphology and host associations; precise identification requires examination of gall structure and host specificity
• Other Cynipidae on white oaksMany oak gall wasps induce galls on similar hosts; Druon ignotum is distinguished by the woolly, clustered, vein-associated agamic galls

• gall wasp
• oak gall
• Cynipidae
• heterogony
• white oak
• North America

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy