Balgus Fleutiaux, 1920

Barbosa, Felipe Francisco, 2016, Revision and phylogeny of the genus Balgus Fleutiaux, 1920 (Coleoptera, Elateridae, Thylacosterninae), Zootaxa 4083 (4), pp. 451-482 : 454-455

Balgus Fleutiaux, 1920

( Figures 1–9 )

[=subgenus Pterotarsus (Pterotarsus) Bonvouloir, 1875: 830 , 831, 832, 833].

Balgus Fletiaux, 1920: 95 , 97, 98 (original description); Schenkling, 1928: 7 (catalogue); Blackwelder, 1944: 275 (catalogue); Chassain & Touroult, 2010: 21 (catalogue).

Type species: Melasis tuberculosa Dalman, 1823 , Fleutiaux (1920) designation.

Diagnosis. Pronotal tubercles present ( Figure 1 ); elytra entirely covered with tubercles, tubercles only on basal region or without tubercles; antennal pocket deep, located mesally on hypomeron, following notosternal suture; tarsomeres 2–4 with elongate ventral lobes, and yellow setae.

Redescription. Body elongate and convex; obconical, subcylindrical or cylindrical. Dorsal and ventral region covered with pubescence of variable density, length, location and color (gold to silver). Color patterns vary from black, brown to yellow.

Head: Hypognathous. Median anterior region with depression or longitudinal groove of variable length and depth. Eyes wide, ocular index (EI) of Calder (1996) between 0.46 and 0.31; finely faceted. Flabellate antenna; fourth to tenth antennomeres shorter and narrower than the others; densely covered with short setae; second antennomere about twice as long as the third, and inserted obliquely into the fourth. Labrum visible and sclerotized. Mandibles almost as long as wide, mesally curved at apex and bidentate.

Thorax: Pronotum ( Figure 1 ) covered with tubercles, more or less notable in various patterns. Tubercles from each side of pronotum are separate from the base to the apex by a median longitudinal groove. Posterior margin of scutellum widely rounded or truncated. Elytra convex and elongate; entirely covered with tubercles, tubercles only on the basal region or without tubercles; epipleuron reduced. Hind wing with well-developed radial and cubital anal cell; cubital anal cell apically oblique; median area of hind wing with five free nervures. Antennal pocket deep, located mesally on hypomeron, following notosternal suture. Mesepisternum and mesepimeron fused. Mesocoxal cavity closed. Metaventrite elongate, slightly smaller than the prosternum. Metacoxal plate well developed. Tibiae strongly expanded and flattened dorsoventrally, with a depression where the tarsus is fitted. Tarsomeres 2–4 with elongated ventral lobes and yellow setae.

Abdomen: Five visible ventrites, four basal connate. Ventrite 5 triangular, subtriangular or pentagonal; other ventrites rectangular or subpentagonal. Ventrite 4 with gold or light brown thin transversal strip on posterior margin.

Female genitalia: Symmetrical. Styli absent, baculum and coxite elongate. Coxite apically inserted in relation to the baculum, with or without setae. Baculum at least 4 times as long as the coxite.

Male genitalia: Aedeagus trilobed. Parameres acuminate or rounded at apex. Penis with acuminate apex. Median strut present and elongate. Phallobasis symmetrical or slightly asymmetrical; dorsal surface with concavity, normally confined to base or expanded from base to apex, reaching or not up to limit of parameres.

Sexual dimorphism: Males with antennal rami setae significantly longer than females ( Chassain & Touroult 2013).

Size variation: (N = 107): length 9.40–25.60 mm (mean = 15.35 mm); humeral width 3–7.70 mm (mean = 4.85 mm).

Etymology. When Fleutiaux (1920) described the genus Balgus he did not make any mention of etymology.

Distribution. Neotropical—Belize, Bolivia, Brazil, Colombia, Ecuador, Guyana, French Guiana, Mexico, Nicaragua, Panama, Peru and Trinidad & Tobago ( Figures 12–15 ).

Figures

FIGURE 1. Balgus tuberculosus (Dalman, 1823), pronotum showing tubercles and names, dorsal view.

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 3. Balgus eganensis (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 4. Balgus eschscholtzi (Laporte, 1835): 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; G) aedeagus, dorsal view; H) aedeagus, lateral view; I) aedeagus, ventral view. The genitalia apex oriented to the bottom of the page. Genitalia scales: 0.5 mm, other scales: 2 mm.

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 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 7. Balgus rugosus (Blanchard, 1843): 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. Genitalia scales: 0.5 mm, other scales: 2 mm.

FIGURE 8. Balgus schnusei (Heller, 1914): 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. Genitalia scales: 0.5 mm, other scales: 2 mm.

FIGURE 9. Balgus tuberculosus (Dalman, 1823): 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; G) aedeagus, dorsal view; H) aedeagus, lateral view; I) aedeagus, ventral view. The genitalia apex oriented to the bottom of the page. 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).

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

FIGURE 14. Geographical distribution of Balgus rugosus (Blanchard, 1843).

FIGURE 15. Geographical distribution of Balgus tuberculosus (Dalman, 1823), Balgus subfasciatus (Bonvouloir, 1875) and Balgus schnusei (Heller, 1914).