Balgus obconicus ( Bonvouloir, 1875 )

Barbosa, Felipe Francisco, 2016, Revision and phylogeny of the genus Balgus Fleutiaux, 1920 (Coleoptera, Elateridae, Thylacosterninae), Zootaxa 4083 (4), pp. 451-482 : 462-463

Balgus obconicus ( Bonvouloir, 1875)

( Figure 6 )

Pterotarsus obconicus Bonvouloir, 1875: 831 , 838 (original description).

Balgus obconicus 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 described).

Diagnosis. Obconical body ( Figures 6A, B, C, F ); light brown or yellow on the apical third of elytra, large black band on basal two thirds of elytra; dorsal and ventral region covered with yellow or golden pubescence, moderately dense in head and pronotum, scattered on elytra; ventrite 5 pentagonal, much longer than wide, then gradually narrowed to two thirds, on this point abruptly and obliquely narrowed, without longitudinal median carina, acuminate at apex.

Redescription. Obconical body, narrowing gradually and strongly on posterior two thirds. Elytra about three times as long as pronotum. Dorsal and ventral region covered with yellow or golden pubescence, moderately dense on head and pronotum, scattered on elytra. Tubercles of pronotum more salient than tubercles of elytra.

Color: first, second and third antennomeres dark brown, other antennomeres dark brown or black; antennal rami brown, yellow apically. Head and pronotum black. Elytra dark brown, darker at base, which varies from black to dark brown; regions with tubercles varies from black to dark brown. Light brown or yellow on apical third of elytra, a large black band on the basal two thirds of elytra. Ventral region dark brown. Legs dark to light brown; tarsi light brown or yellow.

Head ( Figure 6D ): punctate, with deep longitudinal median anterior depression, continues posteriorly on longitudinal groove on the vertex, not V-shaped. Eye with spherical surface in lateral view, dorsal margin not sinuous.

Thorax: subcylindrical prothorax ( Figures 6A, B, C, F ), almost as long as wide; margins sinuous; tubercles prominent; posterior half of pronotum with posterolateral oblong tubercle, posterolateral rounded tubercle and posteromedian rounded tubercle; anterior half of the pronotum with anterolateral oblong tubercle, anterolateral rounded tubercle and anteromedian rounded tubercle. Pronotal sculpture formed by deep punctations, sparser and denser on intervals of the tubrcles. Scutellum rectangular to trapezoidal, little longer than wide, margins subparallel, posterior margin rounded, not carinate. Lateral thoracic sclerites hidden under elytra. Antennal acetabulum shallow next to prosternal process. Prosternal process gradually attenuate toward posterior margin; margin more or less rounded. Prosternum, mesoventrite and metaventrite with weak and low density punctations. Elytra ( Figures 6A, C, F ) finely and sparsely punctated; apex rounded; fifth of elytra with five elevated striae and with tranverse rugosities. Two elongated central tubercles, which seem to be a continuation of second basal stria, first in middle and second in posterior third; less elongated lateral tubercle, which seems to be a continuation of the fourth basal stria; another lateral tubercle which seems to be a continuation of fifth basal stria.

Abdominal ventrites: finely punctate; ventrite 5 ( Figure 6E ) pentagonal, much longer than wide, then gradually narrowed to two third, on this point abruptly and obliquely narrowed, without longitudinal median carina, acuminate at apex.

Female genitalia: apex of available female genitalia was damaged; only the baculum could be observed. Baculi, separated by about width of a baculum, at least at the apical third.

Aedeagus: paramere tapering as it approximates apex; acuminate at apex, with many setae. Penis tapering apically; acuminate at apex, slightly curved ventrally in lateral view; apex extends far beyond apex of paramere. Phallobasis approximately three times as long as paramere; about three paramere width. Concavity of phallobasis in dorsal view, limited to base of phallobasis (based on Chassain & Touroult, 2013).

Intraspecific variation: size variation (N = 3): length 11.50–13 mm (mean = 12.50 mm); humeral width 3.90– 4.20 mm (mean = 4.03 mm).

Remarks. the punctations in this species are weak and sparse compared with other species of the genus. Along with B. schunsei , the pronotal tubercles are salient and more clearly separate. The large black band on the basal two thirds of the elytra is similar, but broader than in B. humilis .

Etymology. obconicus , from Latin, “obconical”, referring to the shape of the body of the species.

Material examined. 1 ex., Bolivia, Santa Cruz, Potrerillos del Guendá , 40km, NW, Santa Cruz de la Sierra, 17°40'26"S, 63°27'44"W, 5–20/XI/2004 ,, B. K. Dozier col., black light trap, FDACS ; 1 ex., Brazil, Rio Grande do Sul (RS), 12°31'S, 51°46'W, R. A. Beaver col. 29/X/1968, C. M. F. von Hayek det., 1960, Brit Mus. 1974-435, BNHM ; 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 (RS) and French Guiana ( Figure 13 ).

Type locality. French Guiana, Cayena.

Figures

FIGURE 6. Balgus obconicus (Bonvouloir, 1875): A) habitus, dorsal view; B) habitus, ventral view; C) habitus, lateral view; D) head, frontal view; E) ventrite 5, ventral view; F) pronotum and elytra, dorsal view. Scales: 2 mm.

FIGURE 13. Geographical distribution of Balgus obconicus (Bonvouloir, 1875) and Balgus humilis (Bonvouloir, 1875).