Clustered Midrib Gall Wasp
Andricus dimorphus
This record describes Andricus dimorphus (species). Recorded family: Cynipidae. Recorded order: Hymenoptera.
Identification and Appearance
Forms galls on leaves in the white oak group. Galls in rounded masses, a few to 30 in each, closely packed, clustered on the under side of the midrib or petiole, one-celled, globose, pointed basally, greenish, tinged with pink when fresh, grayish when old, individual galls, diameter 1/10 to 1/8 inch, diameter of masses from 1/4 to 1/2 inch, on white, burr and chestnut oaks. In addition to these hosts ( Quercus alba, Q. macrocarpa, and Q. prinus ), Weld lists Q. prinoides (dwarf chinkapin oak), and notes that there is a similar gall on Q. laceyi .
Classification
- Kingdom
- Animalia
- Phylum
- Arthropoda
- Class
- Insecta
- Order
- Hymenoptera (Ants, Bees, Wasps and Sawflies)
- Superfamily
- Cynipoidea
- Family
- Cynipidae (Gall Wasps)
- Tribe
- Cynipini
- Genus
- Andricus
Imported taxonomy record. Source availability varies; see the source references and editorial policy below.
Diet and Behavior
Life History
Weld reports that adults emerged from collected galls in the second, third, and fourth springs, in late March or early April.
About Flies: the wider group
Order-level background for Hymenoptera, the group containing Andricus dimorphus. Species-specific details appear above.
Group overview
Hymenoptera includes over 150,000 described species of ants, bees, wasps, and sawflies. Earth harbors approximately 20 quadrillion (20×10^15) ants, with a combined biomass of ~12 megatons of dry carbon - exceeding the combined biomass of all wild birds and mammals (PNAS, 2022).
Ecological role of the group
About 35% of the world's food crops depend on animal pollinators. The chocolate industry, valued at over $100 billion, depends on pollinating flies and midges. Ants are the dominant soil engineers in most terrestrial ecosystems, turning more soil than earthworms in many habitats.
Economic and practical significance of the group
Pollinators contribute $235-577 billion worth of annual global food production (FAO). In the U.S., bee pollination alone benefits crops valued at $18 billion annually, and honey bees are responsible for $5.4 billion in agricultural productivity. Between April 2023-2024, 55.1% of managed honey bee colonies were lost. The U.S. bee population dropped from 5 million to 2.5 million.
Recorded sources for this group: FAO, USDA, EPA, PNAS (2022), US Fish & Wildlife Service. Imported estimates may describe particular regions or reporting periods.
Photos of Clustered Midrib Gall Wasp (2)
Photo credits: Contributed by Charley Eiseman; Additional contributions by john and jane balaban