Sensilla on antennae and mouthparts of immature and adult Hypochlora alba (Dodge), a monophagous grasshopper, were observed with a scanning electron microscope. The antenna contains sensilla trichodea (s.t.) on the scape and pedicel and four types of sensilla brasiconica (s.b.) on the flagellum. The s.b. include long, thick-walled uniporous and short, multiporous chemoreceptors. Males have 50 to 80% more s.b. types I to III than females. Sensilla coeloconica with strongly ribbed pegs are abundant. Rows of cuticular plates with apical papillae ring the distal margins of flagellar segments. A rosette of cuticular plates occurs on the dorsal side of the antepenultimate segment. Maxillary and labial palpi have the same types and distribution of sensilla which include long s.t. primarily on the distal segment and four types of s.b. Types III and IV s.b. are terminal chemoreceptors on the distal segment; the predominant type III is ribbed and uniporous. The total number of terminal sensilla is less than that on polyphagous species of grasshoppers. The posterior surface of the clypeo-labrum contains three asymmetrical pairs of hair tracts, a central hair group and three types of s.t. Four types of chemoreceptor groups occur (A1 to A3, A10) which consist of pegs, domes or bulbous sensilla. Other bulbous sensilla present are types 9, 11, and 12, the latter forming longitudinal strands of pillow-like structures. Type 13 hairs are elongations of swollen areas on longitudinal strands.