Balgus humilis ( Bonvouloir, 1875 )

Barbosa, Felipe Francisco, 2016, Revision and phylogeny of the genus Balgus Fleutiaux, 1920 (Coleoptera, Elateridae, Thylacosterninae), Zootaxa 4083 (4), pp. 451-482 : 460-462

Balgus humilis ( Bonvouloir, 1875)

( Figure 5 )

Pterotarsus humilis Bonvouloir, 1875: 833 , 837 (original description).

Balgus humilis Fleutiaux, 1920: 97 (new combination); Schenkling, 1928: 7 (catalogue); Blackwelder, 1944: 275 (catalogue); Chassain & Touroult, 2010: 21 (catalogue); Chassain & Touroult, 2013: 75, 76, 77, 79, 81 (redescription, aedeagus described).

Diagnosis. Subcylindrical body ( Figures 5A, B, C, F ); light brown or yellow on apical third of elytra, large black band on basal two thirds of elytra; dorsal and ventral regions covered with yellow or golden pubescence, moderately dense in head and pronotum, scattered on elytra; ventrite 5 with short conspicuous longitudinal median carinae.

Redescription. Subcylindrical body, narrowing on the posterior third. Elytra about two and a half times as long as pronotum. Dorsal and ventral region covered with yellow or golden pubescence, moderately dense on head and pronotum, scattered on elytra.

Color: first antennomere dark brown, other antennomeres dark or light brown; antennal rami brown, yellow apically. Head and pronotum black. Elytra dark brown, darker basally, varying from black to dark brown; regions with tubercles vary from black to dark brown. Light brown or yellow on apical third of elytra, large black band on basal two third of elytra. Ventral region dark brown. Legs dark to light brown. Tarsi light brown or yellow.

Head ( Figure 5D ): punctate, with deep longitudinal median anterior depression, continues posteriorly on the longitudinal groove on vertex, V-shaped. Eye with spherical surface in lateral view, dorsal margin not sinuous.

Thorax: subcylindrical prothorax ( Figures 5A, B, C, F ), almost as long as wide; sinuous margins; abruptly attenuate on anterior third; prominent tubercles; posterior half of pronotum with posterolateral oblong tubercle; 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 punctuations becoming sparser, denser on intervals of tubercles. Scutellum rectangular to trapezoidal, slightly longer than wide, subparallel margins, 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 densely punctuate. Elytra ( Figures 5A, C, F ) finely and sparsely punctuate; subacuminate apex; fifth basal with five elevated striae and with tranverse rugosities. Two elongated central tubercles which seem to be a continuation of second basal stria, first at middle and second in posterior third; less elongated lateral tubercle, which seems to be a continuation of fourth basal stria; another lateral tubercle seems to be a continuation of fifth basal stria.

Abdominal ventrites: densely punctate; ventrite 5 ( Figure 5E ) triangular, with short conspicuous longitudinal median carina; strong and gradually narrowed from base to apex, which is truncated, not curved.

Female genitalia ( Figure 5G ): baculum about 5.5 times as long as coxite; baculi, at least in apical third, separated by about width of a baculum. Coxites without setae.

Aedeagus: paramere tapering apically; acuminate at apex and with maximum of three setae. Penis tapering to apex; acuminate at apex, slightly curved ventrally in lateral view. Phallobasis about twice as long as paramere; about three times the paramere’s width. Concavity of the phallobasis in dorsal view, limited to base of the phallobasis (based on Chassain & Touroult, 2013).

Sexual dimorphism: males have longitudinal median carina of ventrite 5 with three, four or five teeth, while the females have only one tooth.

Intraspecific variation: size variation (N = 11): length 10.90–15.70 mm (mean = 13.93 mm); humeral width 3.40–5.10 mm (mean = 4.40 mm).

Remarks. Balgus humilis and B. tuberculosus are very similar, but the first can be easily distinguished by the light brown to yellow coloration on the apical third of the elytra with a black small oblique tubercle next to each suture. In B. humilis the longitudinal groove at the apex of the head is less deep than in B. tuberculosus and B. eganensis .

Etymology. humilis , from Latin, “humble”, (adjective).

Material examined. 1 ex., Brazil, Goiás (GO), Rio Verde, E. Fleutiaux coll., MNHN; 1 ex., Brazil, Minas gerais (MG), Ipatinga, A. M. Bello col., XI/1994, FIOCRUZ; 1 ex., Brazil, Santa Catarina (SC), Hansa Humboldt (currently municipality of Colorupá), Reitter, MNHN; 1 ex., French Guiana, Cayena, 331-62, J. Chassain det., 2011, MNHN; 1 ex., French Guiana, (illegible), 25-62, MNHN; 1 ex., French Guiana, Roches de Kourou, Le Moult coll., E. Fleutiaux coll., MNHN; 1 ex., Nicarágua, Chontales, E. Fleutiaux coll., MNHN; 1 ex., Nicarágua, Chontales, D. Sharp coll. 1905-313, BNHM; 1 ex., Nicarágua, Chontales, T. Belt col., J. Muona det., 1982, BNHM; 1 ex., Trinidad & Tobago, Trinidad, Simia, Arima /Blanchisseuse Road., 27/VII/1975, J. Price col., black light trap, FDACS; 2 exs., Trinidad & Tobago, Trinidad, G. E. Bryant col., (?)/ I/1903, G. E. Bryant coll. 1919-147, BNHM.

Distribution. Brazil (GO, MG & SC), French Guiana, Nicaragua and Trinidad & Tobago ( Figure 13 ). Type locality. French Guiana, Cayena (Mniszech coll.).

Figures

FIGURE 5. Balgus humilis (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; G) female genitalia, dorsal view, apex oriented to the bottom of the page, apex damaged. Genitalia scales: 0.5 mm, other scales: 2 mm.

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