Female. Elliptical, black, shining moderately clothed with narrow, white scales; elytra with a subtriangular patch of broader white scales each side of scutellum; a black patch of scales behind scutellum. Rostrum one-third longer than pronotum, moderately stout, strongly arcuate, abruptly bent back near base; smooth at middle, coarsely, densely punctate laterally. Antennae inserted at middle; second segment of funicle half again as long as third, 3-6 equal. Club ovate, finely, densely pubescent. Head finely punctate; transversely grooved between eyes at base of rostum. Pro thorax strongly convex, sides arcuate, converging to constriction at apex; densely, coarsely punctate on pronotum, punctures confluent laterally, a smooth median line from base to apex; clothed with transversely arranged narrow, white scales, denser before scutellum. Scutellum rhomboidal, longitudinally impressed, denuded. Elytra triangular, slightly wider than pronotum, sides converging to apex, widest behind humeri; not impressed along suture; striae deeply impressed, punctures very small, shallow; intervals with a double line of deep punctures; each interval with a double line of narrow white scales; black patch of scales behind scutellum occupy intervals 1 and 2 of middle disc. Ventral side densely clothed with broad scales except at middle of abdominal segments 3, 4, and 5 which are denuded. Prosternum deeply sulcate, densely, coarsely punctured. Abdominal segments finely, densely punctate except at middle of segments 3 and 4; fifth abdominal segment with coarser punctation and a shallow depression at middle. Legs clothed with narrow, white scales. Claws large, divergent, simple. Length 4.8 mm, width 2.5 mm.
Male. Rostrum bisulcate anterior to point of insertion of antennae, lateral punctation coarser. Prosternum deeply sulcate, armed with two short spines; first and second abdominal segments broadly depressed at middle, depression densely clothed with erect, white pubscence; fifth abdominal segment without depression at middle.
Type Locality. Holotype, female, Patagonia Mts., Ariz. VIII-7-50, DJ & JNK. Allotype same data. Both in (OSU). Nineteen paratypes: 12 same data as types in (OSLJ); 6 same data in (ELS); 1 Nogales, Ariz. IX-2-38, DJ & JNK. in (OSU).
Found on the flowers of Acacia sp. in the Patagonia Mts. Closely related to C. basinotata (Champion) from the mountains of Guerro, Mexico. C. basinotata differs in that it lacks the black patch of scales, has on each interval "a narrow line of fuscous scales, intermixed with larger ones," and the first abdominal segment only is depressed in the male.
Recognition. Geraeus patagoniensis is a robust, 3.1–5.2 mm long species with a distinct color pattern. The dorsal vestiture consists of slender, indistinctly scalloped scales, usually arranged in a single row per interstria. The dark spot on the elytral disk consists of fuscous scales and can be reduced in small-sized specimens. Geraeus modestus tends to be wider, has ovate scales, longer prosternal spines, and few hairs in the ventral depression of the male. Geraeus patagoniensis is closely related to G. basinotatus Champion, a slightly differently scaled species occurring from central Mexico to Colombia.
Distribution. This species occurs in the northern Sierra Madre Oriental and has been collected frequently in southern Arizona (Fig. 75). Type locality. Patagonia Mountains, Arizona.
Material examined. United States: Arizona (CMNC 4, CWOB 33, JPPC 19, TAMU 8, USNM 9). Mexico: Chihuahua (JPPC 1, USNM 3), Sonora (CMNC 3, CWOB 2, TAMU 1). Total 83 specimens.
Temporal occurrence. July to September.
Plant associations. Asclepiadaceae: Asclepias sp. (J. Prena, observation). Asteraceae: Baccharis salicifolia (Ruiz and Pav.) Pers. [as B. glutinosa Pers.] (R. A. Alexander, observation), Senecio flaccidus Less. [as S. longilobus Benth.] (R. A. Alexander, observation). Euphorbiaceae: Cnidoscolus angustidens Torr. (R. A. Alexander, observation), Croton sp. (USNM 1).