Thecavermiculatus carolynae n. sp. from the Pacific coastal area of California is described from female, male, and juvenile (J2) specimens reared on Festuca megalura Nutt. in the greenhouse. Differences between females of T. carolynae and those of its closest relative, T. gracililancea Robbins, 1978, include shorter stylet, shorter length, and lesser length of the vulval slit. Of these two species, males have been found only for T. carolynae. The habitats of the two species are vastly different: T. gracililancea has been found only in shallow clay soil near hilltops in an area subject to high summer temperatures where the soil becomes brick-like during the summer; T. carolynae has been found only in deep sandy soil of a creek bottom subject to cool summer temperatures where the soil remains moist. Key words: Festuca megalura, foxtail rescue, habitat, morphology, new species, scanning electron microscopy, taxonomy, Thecavermiculatus carolynae n. sp.