The treehopper Micrutalis discalis (Walker), subfamily Smiliinae, tribe Micrutalini, was described in 1858 from Veracruz, Mexico. We report the first U.S. records from five counties in Arizona, describe the male and fifth instar for the first time, and redescribe the female. We collected nymphs and adults from desert mistletoe (Phoradendron californicum Nutt.; Viscaceae), which was hemiparasitic on trees and shrubs of the Fabaceae: yellow paloverde (Parkinsonia microphylla Torr.), velvet mesquite (Prosopis velutina Wooten), and catclaw acacia (Senegalia greggii [A. Gray] Britton and Rose). Our observations of nymphs in both late March to early May and in August suggest that M. discalis is bivoltine. We collected another adult, perhaps incidental, from the mistletoe Phoradendron villosum (Nutt.) Nutt. on Sonoran scrub oak (Quercus turbinella Greene; Fagaceae) and consider an adult from mule-fat (Baccharis salicifolia [Ruiz. and Pav.] Pers.; Asteraceae) an incidental occurrence.