Balgus albofasciatus ( Bonvouloir, 1875 )

Barbosa, Felipe Francisco, 2016, Revision and phylogeny of the genus Balgus Fleutiaux, 1920 (Coleoptera, Elateridae, Thylacosterninae), Zootaxa 4083 (4), pp. 451-482 : 455-457

Balgus albofasciatus ( Bonvouloir, 1875)

( Figure 2 )

Pterotarsus albofasciatus Bonvouloir, 1875: 832 , 841 (original description).

Balgus albofasciatus Fleutiaux, 1920: 97 (new combination); Schenkling, 1928: 7 (catalogue); Blackwelder, 1944: 275 (catalogue); Chassain & Touroult, 2010: 21 (catalogue); Chassain & Touroult, 2013: 76, 77, 79, 81 (redescription, aedeagus description).

Diagnosis. Subcylindrical body ( Figures 2A, B, C, F ); dorsal and ventral region covered with whitish to gray pubescence, moderately dense on the head and pronotum, denser on light brown bands on the elytra; posterior angle of the pronotum with a short and oblique carina; scutellum not carinate; elytra without tubercles; longitudinal median carina of ventrite 5 with four small teeth.

Redescription. Subcylindrical body, narrower on the posterior third. Length of elytra about three times as long as pronotum. Dorsal and ventral region covered with pubescence, whitish to gray, moderately dense on the head and pronotum, denser on light brown bands on the elytra.

Color: shiny black, except for first and second antennomeres dark brown with remaining antennomeres light brown; antennal rami yellow; legs dark brown; tarsi light brown or yellow. Elytra with two light brown bands: basal band originates on the basal third, following the elytral margin, then extending towards the apex to about half the length of elytra, which curves itself towards the base, sinuous up to suture; the apical band originates on the apical third on the elytral margin, extending towards the apex, up to the suture.

Head ( Figure 2D ): densely punctate, with a deep longitudinal median anterior depression, that extends to the vertex, which is replaced by a thin line. Eye with a spherical surface in the lateral view, dorsal margin not sinuous.

Thorax: subcylindrical prothorax ( Figures 2A, B, C, E, F ), almost as long as wide; margins sinuous; posterior angle with a short and oblique carina; tubercles short, conspicuous; posterior half of the pronotum with posterolateral rounded tubercle and posteromedian rounded tubercle; anterior half of the pronotum with anterolateral rounded tubercle and anteromedian rounded tubercle. Pronotal sculpture formed by deep punctations, sparser and denser in the intervals of the tubercles. Scutellum subrounded, slightly longer than wide, not carinate. Lateral thoracic sclerites hidden under the elytra. Antennal acetabulum shallow next to the prosternal process. Prosternal process gradually attenuate towards the posterior margin; lateral margin slightly rounded. Prosternum, mesoventrite and metaventrite densely punctate. Elytra ( Figures 2A, C, F ) finely and sparsely punctated, thinner and denser punctations on light brown bands; subacuminate apex; fifth of the elytra with four elevated striae and without roughness; elytral striae not elevated on the rest of the elytra; without tubercles.

Abdominal ventrites: densely punctate; ventrite 5 ( Figure 2H ) triangular, with longitudinal median carina forming four small teeth; strong and gradually narrowed from base to apex, which is truncated, not curved.

Female genitalia ( Figure 2G ): baculum about 6 times as long as coxite; separated by approximately the width of the baculum, at least on the apical third. Coxites without setae.

Aedeagus: paramere tapering next to the apex; acuminate apically and without setae; constriction on about half of the paramere’s length. Penis tapering apically; acuminate at the apex. Phallobasis about two and a half times as long as the paramere; about three times as wide as paramere. Concavity of the phallobasis in dorsal view, expanded from the base to the apex, reaching the limit of the parameres (based on Chassain & Touroult, 2013).

Itraspecific variation: size variation (N = 3): length 12.60–13.40 mm (mean = 13 mm); humeral width 4.10– 4.20 mm (mean = 4.16 mm).

Remarks. Balgus albofasciatus is the only known species of the genus that has no setae on the parameres. Based on the original descriptions Balgus albofasciatus and B. subfasciatus are very similar species; however, we did not have access to specimens of the second. Balgus subfasciatus can be distinguished from B. albofasciatus by the presence of an elytral suboval tubercle, covered with strong rugosities. These two species are the only ones of the genus that have only white to silver setae, while in the other species examined only golden to yellow setae or a combination of these last two types were found. These two species are the only ones with a short oblique carina on the posterior angle of the pronotum.

Etymology. [albus + fasciatus]. albus, from Latin, “white”, fasciatus, from Latin, “with bands”, in reference to the elytral pattern of white bands.

Material examined. 2 exs., Bolivia, Santa Cruz, 3,7 km SSE Buena Vista, Hotel Flora & Fauna, 430 m, 15– 22/XI/2001, B. K. Dozier coll., black light trap, Tropical transition forest, FDACS ; 3 exs., Brazil, Rondônia (RO), 62 Km SW Ariquemes, near to Fazenda Rancho Grande , 4–16/XI/1997, J. E. Eger col., black light trap, FDACS ; 1 ex., French Guiana, Cayena , 494-64, E. Fleutiaux det., MNHN ; 1 ex., French Guiana, Cayena , 494-64, MNHN ; 1 ex., French Guiana, RN2 PK65, 20/IX/2008, SEAG, glass trap, J. Chassain det., 2009, Don J. Chassain , I.G.: 31.315, IRSN .

Distribution. Bolivia, Brazil (RO) and French Guiana ( Figure 12 ). Type locality. French Guiana, Cayena.

Figures

FIGURE 2. Balgus albofasciatus (Bonvouloir, 1875): A) habitus, dorsal view; B) habitus, ventral view; C) habitus, lateral view; D) head, frontal view; E) pronotum, lateral view; F) pronotum and elytra, dorsal view; G) female genitalia, dorsal view, apex oriented to the bottom of the page; H) ventrite 5, ventral view. Genitalia scales: 0.5 mm, other scales: 2 mm.

FIGURE 12. Geographical distribution of Balgus albofasciatus (Bonvouloir, 1875), Balgus eganensis (Bonvouloir, 1875) and Balgus eschscholtzi (Laporte, 1835).