A new soldier-producing aphid species, Pseudoregma baenzigeri, sp. nov., from Northern Thailand.

Pseudoregma baenzigeri, sp. nov., is described from northern Thailand. This species forms dense, huge colonies on shoots of the bamboo Dendrocalamus sp., and produces many first-instar, pseudoscorpion-like soldiers. Alate sexuparae were found from the end of September to mid October. Two syrphids, Eupeodes sp. A (allied to E. confrater) and Dideoides chrysotoxoides, and the pyralid Dipha aphidivora were recorded as predators of P. baenzigeri. The aphids were also likely to be eaten by some rodents. The apterous adult, nymphs, soldier and alate sexupara of P. baenzigeri can be distinguished from those of the other congeners by the longer, conical ultimate rostral segment. A tentative key to the species of Pseudoregma living on bamboo is provided.