Rhysium Pascoe, 1866

Santos-Silva, Antonio, Galileo, Maria Helena M. & Wappes, James E., 2017, Descriptions, notes and reassignments in Neoibidionini (Coleoptera: Cerambycidae: Cerambycinae) with a new genus, three new species and keys to species of Brechmoidion Martins, 1969, Compsibidion Thomson, 1864 and Rhysium Pascoe, 1866, Insecta Mundi 2017 (560), pp. 1-21 : 13-15

On Rhysium Pascoe, 1866 and Rhysium bimaculatum Pascoe, 1866

( Fig. 19–26 , 38 )

Pascoe (1866) defined Rhysium as follows: “The head is short and concave in front; the antennary tubers are stout and divergent; the eyes are broadly emarginate; the antennae are without spines, as long as the body in the female, and half as long again in the male, the scape is subpyriform, the third joint is twice the length of the scape in both sexes; the rest of the joints in the female are not longer than the scape, in the male they are considerably longer; the prothorax is oblong, broader in the middle, its disk marked with three nearly obsolete tubercles; the elytra are narrow and elongate, and rounded at the apices; the legs are compressed, the femora thickened, the four posterior tarsi equal; the pro- and mesosterna depressed, the latter elongate.”

According to Martins (1969), Rhysium is characterized as follows (translated): “Frons irregular, pubescent; lateral foveae well-marked; antennal tubercles slightly developed, rounded at apex, with longitudinal carinae and sulci between its bases; vertex with sericeous pubescence. Scape gradually thickened toward apex, without sulcus on dorsal side of the base, finely pubescent; antennomere III slightly (male) or longer (female) than IV, carinate; antennomere IV slightly shorter or subequal than V; antennae in male distinctly longer than in females. Prothorax cylindrical, slightly constricted anteriorly and posteriorly; pronotum pubescent, with 5 slightly distinct tubercles, without transverse roughness. Elytra unarmed at apex; setae variable. Profemora thickened, with peduncle not very short and not depressed on outer side; metafemora unarmed at apex; hind tibiae finely or not ( bimaculatum ) carinate; metatarsomere I (male of bimaculatum ) slightly elongate.”

Later, Martins and Galileo (2007) defined the genus as follows (translated): “Antennal tubercles rounded at apex, with sulci and carinae between its bases. Antennae in male longer than in female. Scape subcylindrical, without basal sulcus. Antennomere III (male) slightly longer than IV that is subequal or slightly shorter than V. Prothorax cylindrical. Pronotum pubescent and with 5 slightly marked tubercles. Elytra with rounded apex. Apex of metafemora normal. Metatibiae carinate or not.”

The following inconsistencies (considering only specimens of R. bimaculatum ) were found in the description and redescriptions of Rhysium :

Pascoe (1866):

1. Antennae in female ( Fig. 19–20 ) are usually slightly longer than body (surpassing elytral apex by about 1.5 antennomere), but may be distinctly longer (surpassing elytral apex by about 2.5 antennomeres);

2. Antennae in male are longer than 1.5 times body length (including in a syntype male), in some males examined more than 1.7 times body length ( Fig. 21 );

3. Antennomere III ( Fig. 19–21 ) is shorter than twice the length of scape in both sexes (including in syntypes);

4. Antennomeres IV–VIII in females ( Fig. 19–20 ) may be at times longer than scape.

Martins (1969):

1. In the redescription of R. bimaculatum it was pointed out that (translated): “In the scape: one of the specimens examined, a female, shows on dorsal side of the base a very distinct and elongate sulcus; in all other specimens this sulcus does not exist.” We are sure that this specimen is the paratype female of R. contracticorne Martins, 1960 from Peru, belonging to MZSP collection. We find that this sulcus is distinct from base to near apex, although somewhat deeper in basal third ( Fig. 22 ). Also, according to Charyn Micheli (USNM) regarding the types of R. contracticorne (personal communication): “The two specimens from Peru do have a very slight sulcus as you mention, though it is harder to see from some angles. In the others from Bolivia, including the holotype, Ido not see anything.” And, according to Eugenio H. Nearns (PERC – personal communication) there is no sulcus on dorsal side of the scape of the syntype male of R. bimaculatum . In the series of specimens of R. bimaculatum examined by us, the sulcus is absent ( Fig. 26 ) or slightly indicated (except in the paratype female of R. contracticorne ). This suggests that the presence of a distinct sulcus, although not common, is not an aberration. As Martins (1969) recorded that the scape in Rhysium is not dorsally sulcate, apparently he also considered the sulcus in the paratype female to be an aberration.

2. Although the metatibia is not carinate, it is longitudinally sulcate laterally. The sulcus is shallow and in some specimens can be less distinct.

3. Additionally, the elytral pubescence is variable in the specimens examined: sparse in basal third and gradually somewhat denser toward apex ( Fig. 23, 25 ), or sparse throughout ( Fig. 24 ).

Summary: Variable character states in Rhysium bimaculatum include: the length of both male and female antenna; the presence of a dorsal basal sulcus on the scape of females; the development of the lateral carina on the metatibia; and the location and amount of elytral pubescence.

Material examined of R. bimaculatum . BOLIVIA, Chaco (Yungas; 3000 m), 1 male, G. Garlepp col. (no date) ( MZSP). Santa Cruz: Refugio Los Volcanes (3400-4200 ft.; 18º06’S / 63º36’W), 1 male, 14 females, 16-20.IX.2012, Wappes, Skelley, Bonaso & Hamel col. ( ACMT) ; 4 km N Bermejo ( Refugio Los Volcanes ; 1000 m; 18º06’S / 63º36’W), 2 females, 4-8.X.2007, Wappes & Morris col. ( ACMT) ; Refugio Los Volcanes ; 1045-1350 m; 18º06’S / 63º36’W), 1 female, 17-24.X.2014, Wappes & Morris col. ( ACMT); ( Refugio Los Volcanes ; 3363’) , 1 female, 1-10.X.2008, Morris & Wappes col. ( RFMC). La Paz: Mapiri (no other data), 1 female ( MZSP) . PERU, San Miguel (5000 ft.), 1 female (paratype of R. contracticorne ), 1.IX.1911, Yale Peruv Exp. col. ( MZSP). Junín: Pampa Hermosa ( Lodge , nr. San Ramon ; 1220 m), 1 female, 6-7.XI.2009, J. Heppner col. ( RFMC). Pasco: Palomas (Eneñas), 1 female, 26.VIII.1983, P. Hockins col. ( MZSP) .

Figures

Figures 19–26. Rhysium bimaculatum. 19) Dorsal habitus, female from Bolivia. 20) Dorsal habitus, paratype female of R. contracticorne from Peru. 21) Dorsal habitus, male from Bolivia. 22) Head and scape, lateral view, paratype female of R. contracticorne from Peru. 23) Elytral apex, male from Bolivia. 24) Elytral apex, paratype female of R. contracticorne from Peru. 25) Elytral apex, female from Bolivia. 26) Head and scape, dorsal view, male from Bolivia.

Figures 27–38. Adult habitus and structures of Rhysium and Brechmoidion spp. 27–30, Rhysium separatum, paratype male: 27) Dorsal habitus. 28) Apex of metafemur. 29) Antennal tubercles. 30) Pronotum. 31–33, Brechmoidion falcatum: 31) Dorsal habitus, paratypefemale. 32) Apex of metafemur, paratype male. 33) Antennal tubercles, paratype male. 34–37, Brechmoidion exicisifrons, paratype male: 34) Dorsal habitus. 35) Apex of metafemur. 36) Antennal tubercles. 37, Pronotum. 38, Rhysium bimaculatum, male, antennal tubercles.