Geraeus nimbatus (Casey)

Prena, Jens, 2009, A Review of the Species of Geraeus Pascoe and Linogeraeus Casey Found in the Continental United States (Coleoptera: Curculionidae: Baridinae), The Coleopterists Bulletin 63 (2), pp. 123-172 : 145

Geraeus nimbatus (Casey)

( Figs. 11, 12 , 74 )

Geraeus penicellus var.; Champion (1909:491). Centrinaspis nimbata Casey 1920:404 . Holotype male, labeled ‘‘Cuernavaca/ Mor.

Mex./ Wickham,’’ ‘‘σ,’’ ‘‘Casey/ bequest/ 1925,’’ ‘‘ Type USNM/ 37848 ,’’

Casey’s handwriting ‘‘nimbatus/ Csy.’’ Geraeus nimbatus ; O’Brien and Wibmer (1984).

Recognition. Geraeus nimbatus is an inconspicuous, 2.6–3.7 mm long species with slender rostrum and elongate second desmomere. The dorsal vestiture is homogeneous and appears rather sparse and coarse ( Fig. 11 ) when compared with uniformly colored G. penicillus , the most common species of this complex in the United States. The two species may be distinguished by the distribution of setae on the funicle and morphological details of the aedeagus. The internal sac of G. nimbatus has a conspicuous, rod-like basal sclerite almost the length of the entire aedeagus, while G. penicillus has a thread-like flagellum. Male G. nimbatus also have long hairs on the ventral edge of the hind tibia.

Distribution. This species has been found in southern Arizona, western Texas, and at various locations in Mexico ( Fig. 74 ).

Type locality. Cuernavaca , Morelos, Mexico .

Material examined. United States: Arizona, Cochise Co., Pima Co., Santa Cruz Co. ( CWOB 3 , JPPC 5 , TAMU 2 , USNM 1 ) , Texas, Jeff Davis Co. ( TAMU 1 ) . Mexico: Campeche ( CMNC 1 ) , Durango ( TAMU 1 ) , Jalisco ( TAMU 3 ) , Morelos ( JPPC 2 , USNM 15 ) , Quintana Roo ( CMNC 1 ) , Sonora ( USNM 1 ) , Zacatecas ( CMNC 4 ) ; Nogales [interception] ( USNM 1 ) . Total 41 specimens.

Temporal occurrence. July to early September.

Plant associations. Asteraceae : A. adenophora [as Eupatorium adenophorum ] (N. L. H. Krauss). Poaceae : Z. mays (interception 1948, USNM).

Note. Geraeus nimbatus was known previously only from a series collected by Wickham in Cuernavaca, which Champion (1908) considered a variety of G. penicillus and of which Casey described a single specimen. The first collection made in the United States dates from 1924. A small male specimen, intercepted with green corn plants at Nogales in 1948, was examined by Buchanan but could not be identified. Southern Arizona likely represents the northern distributional limit of this and other species, such as G. coarctatus , G. euryonyx , G. pannuceus , and G. patagoniensis . The single record from western Texas needs confirmation.

Figures

Figs. 9–16. Geraeus species, dorsal and lateral aspects; scale bar 1 mm. 9, 10) G. euryonyx, female; 11, 12) G. nimbatus, female; 13, 14) G. penicillus, male, maculate form; 15, 16) G. penicillus, female, unicolored form.

Figs. 73–75. Maps of southern United States and Mexico (top) and United States (without northwestern part) and Central America (bottom) showing distributions of G. euryonyx, G. minor, G. nimbatus, G. pannuceus, G. patagoniensis, G. petilior, and Linogeraeus neglectus.