Andricus tumefaciens n. sp.

Gall (Figs 3a-c). Large red-chestnut gall, irregular, woody mass completely surrounding small twigs. Polythalamous, 6x4 cm, too hard to cut. The entire gall is formed of very many distinct but thoroughly fused masses, resulting in a rather irregular gall. The surface is very rough, completely cracked similar to burnt leather, and with raised polygonal portions that are 1-2 mm in diameter, dark or blackish brown, lines separating them much lighter. Galls remain several years in the oak branch, but after months or years become fragile.

Biology. Only the asexual generation is known which induces galls on Quercus chihuahuensis. Distribution. Currently known only from Mexico (Zacatecas).

Etymology. The shape and form of the gall resembles stem tubers caused by Agrobacterium tumefaciens Smith & Townsend (Proteobacteria: Rhizobiales), thus we have given the same specific name to this new species of gallwasp.