New species of Theocolax Westwood (Hymenoptera: Pteromalidae:Cerocephalinae) thought to attack the walnut twig beetle, Pityophthorus juglandis Blackman (Coleoptera: Curculionidae: Scolytinae)

A new species of Theocolax Westwood (Hymenoptera: Pteromalidae: Cerocephalinae) is described from the United States and is one of only three species of Theocolax to be documented in North America.  This new species of Theocolax has been reared in Colorado from wood infested with the walnut twig beetle (Pityophthorus juglandis Blackman) which transmits thousand cankers disease.  The wasp is characterized by a tuft of setae at the apex of the submarginal vein, a patch of horizontal striations on the pronotal side, the post marginal vein being subequal in length to the stigmal vein, the interantennal lamella extending more than half way to the median ocellus, and a large macula behind the stigma vein of the forewing.  In the thousand cankers disease system Cercephalinae pteromalids are the most commonly reared parasitoids and may aid in suppressing P. juglandis in non-native habitats.