Neuroterus anthracinus

The two distinct galls provide the primary means of identification. The oyster gall appears on leaf undersides between midrib and lateral veins, approximately 0.3 cm across, with two persistent valve-like tissue flaps; coloration varies from green to brown, pink, or red-spotted. The April-bud gall is smooth, oval, about 0.8 cm, developing within terminal or axillary bud scales with a clearly visible escape aperture after emergence. Adults are small wasps typical of the genus Neuroterus, with reduced wing venation characteristic of Cynipidae.

Associated with oak trees (Quercus spp.), specifically forming galls on leaves and buds. The oyster gall develops under the lower leaf epidermis; the April-bud gall forms within bud scales.

Native to Europe with records from Belgium, Denmark, and other European countries. Introduced to North America. The species has been observed in both northeastern and Pacific coast regions of the United States and Canada.

Agamic generation females emerge in autumn from oyster galls. Sexual generation emerges from April-bud galls around May. The April-bud gall is of brief duration, with insects emerging within a week of gall formation.

Larvae feed on nutritive plant cells induced within the gall tissue. Adults do not feed; their mouthparts are adapted for emergence from galls rather than feeding.

• Quercus - hostOak species; specific host species not definitively identified in sources

Heterogonous life cycle with alternating generations. The agamic (parthenogenetic) generation develops in unilocular, unilarval oyster galls; females emerge in autumn and lay eggs in buds, inducing the sexual generation. The sexual generation develops in April-bud galls; males and females emerge in spring, mate, and females lay eggs in leaf lamina, inducing oyster galls.

Females of the agamic generation exhibit a specific oviposition behavior, laying eggs within buds to induce the subsequent sexual generation. The species has been observed to form galls through chemical induction of plant tissue, causing multiplication of nutritive cells and abnormal development of infested tissue.

As a gall former, creates microhabitats that support a community of parasites and inquilines. The galls serve as food and refuge for the developing wasp at the expense of the oak host. Sweet secretions produced by cynipid galls attract sugar-feeding wasps such as yellow jackets and paper wasps.

Contributes to oak gall biodiversity studied by naturalists and scientists. The species is part of the complex community of gall wasps that form the basis of research into parasite-host coevolution and biodiversity discovery. No direct economic impact documented.

• Neuroterus quercusbaccarumAlso forms leaf galls on oaks; distinguished by gall morphology (spangle galls vs. oyster gall) and life cycle timing
• Neuroterus numismalisForms disc-shaped spangle galls on oak leaves; differs in gall shape and location from N. anthracinus
• Neuroterus albipesRelated gall wasp on oaks; distinguished by gall characteristics and generation timing

• gall wasp
• cynipid
• oak gall
• heterogony
• parthenogenesis
• leaf gall
• bud gall
• introduced species

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• What’s that on an oak leaf? Animal? Plant? Fungus? Nah, gall insect – Galls wasps, Cynipidae — Bug of the Week
• Zookeys | Blog - Part 6
• Discovery of wasp species previously unknown in the U.S.