A new species of emerald ash borer parasitoid from China belonging to the genus Tetrastichus Haliday (Hymenoptera: Eulophidae).
Tetrastichus planipennisi Yang, new species, is described and illustrated based on individuals reared from mature larvae of the emerald ash borer, Agrilus planipennis Fairmaire (Buprestidae), collected from their galleries in the trunks of Fraxinus mandshurica Rupr. in northeastern China. Tetrastichus planipennisi is a gregarious endoparasite, with 56-92 individuals developing in a single host larva and observed parasitism rates from 32 to 65%. Based on reared field-collected material, the female to male ratio is 2.5:1. It is a koinobiont parasitoid and overwinters as a mature larva. The new parasitoid is a potential biocontrol candidate for A. planipennis.