Pl. Nov. Thurb., 326. 1854.
Bracts 4–7, imbricate, circular to ovate, 1–1.5 mm. Flowers brown or maroon, 1.5–2 mm; sepals similar to bracts; stylar column with apex expanded to 1 mm diam., papillose along margins; anthers 15–21, in ring of ca. 3 rows; ovules mostly 120–200. Seeds mostly 120–200. 2n = 60 + 0–1B.
Phenology: Flowering Jan–May.
Habitat: Open desert scrub
Elevation: 100–1000 m
Ariz., Calif., Nev., N.Mex., Tex., Mexico.
Documented hosts from the flora area are Dalea formosa Torrey, D. frutescens A. Gray, Psorothamnus emoryi Rydberg, and P. polydenius (Torrey) Rydberg (Fabaceae). Other species in these genera apparently serve as hosts in Mexico. The taxonomic limits of Pilostyles thurberi are poorly understood. It is difficult to circumscribe the host range of this taxon.