Phylloteras cupella

The galls induced by this species are diagnostic: urn-shaped leaf galls with a distinctive ombré color gradient—lighter at the apex and darker toward the base. New galls are yellow, red, or mauve; aging galls develop purple coloration; old galls turn brown. The wasp itself is minute (1.3–2 mm) and requires microscopic examination for definitive identification. Distinguishing the adult from other Phylloteras species requires specialist taxonomic knowledge.

Oak-dominated habitats in western North America, specifically woodlands and forests containing host oak species including Arizona white oak, blue oak, Engelmann oak, gray oak, leather oak, netleaf oak, scrub oak, and shrub oak.

Documented in the United States in California, Arizona, and New Mexico. Likely present in adjacent regions of Mexico and Canada based on host oak distribution, though not formally documented there.

• Arizona white oak - gall inductionleaf galls
• blue oak - gall inductionleaf galls
• Engelmann oak - gall inductionleaf galls
• gray oak - gall inductionleaf galls
• leather oak - gall inductionleaf galls
• netleaf oak - gall inductionleaf galls
• scrub oak - gall inductionleaf galls
• shrub oak - gall inductionleaf galls

Gall inducer that manipulates oak leaf tissue to form protective structures for larval development. The galls represent a form of plant–insect interaction that creates novel microhabitats on oak foliage.

• Other Phylloteras speciesInduce morphologically similar urn-shaped galls on oaks; require microscopic examination of adult wasps or detailed gall morphology for separation.
• Other Cynipidae on western North American oaksMany cynipid wasps induce oak galls; the distinctive ombré color gradient and specific host associations help distinguish P. cupella galls.

• gall wasp
• cynipid
• oak gall
• leaf gall
• western North America

• BugGuide
• Wikipedia
• iNaturalist taxon
• NCBI Taxonomy