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 : 471

Key to the species of genus Balgus Fleutiaux, 1920 , adapted from Bonvouloir (1875) and Chassain & Touroult (2013)

The identification key to the species of Balgus was adapted from Bonvouloir (1875) and Chassain & Touroult (2013), with the inclusion of new characters: presence or absence of a pair of yellow pronotal tubercles capable of emitting green light ( Costa, 1984); thoracic sclerites in lateral view partially visible or hidden under the elytra; shape of eye in lateral view; body format; presence or absence of the anterior pronotal tubercles; presence or absence of the longitudinal median carina on ventrite 5 and the number of longitudinal teeth; format of ventrite 5; shape of the elytral apex; and format of the median longitudinal depression in the anterior region of the head.

1. Pronotum with a pair of yellow tubercles capable of emitting green light (bioluminescence) ( Costa, 1984); thoracic sclerites in lateral view partially visible; eye in lateral view with corrugated surface, dorsal margin sinuous; large size (20–26 mm). (Figure 8)................................................................................. Balgus schnusei

- Pronotum without bioluminescent tubercles; thoracic sclerites, hidden under the elytra, not visible in lateral view; eye in lateral view with spherical surface, dorsal margin not sinuous; small to medium size (7.5–18.7 mm) ( Chassain & Touroult, 2013).. 2

2. Elytra covered with diverse tubercles distributed across the elytral surface......................................... 6

- Elytra covered only with an anterior suboval tubercle or without tubercles........................................ 3

3. Posterior angle of the pronotum with short oblique carina ( Figure 2E )........................................... 4

- Posterior angle of the pronotum without short oblique carina.................................................. 5

4. Scutellum carinate; elytra with an anterior suboval tubercle, covered with strong rugosities........... Balgus subfasciatus

- Scutellum not carinate; elytra without tubercles. ( Figure 2 )..................................... Balgus albofasciatus

5. Subcylindrical body; dorsal and ventral regions covered with moderately dense pubescence on head and pronotum, much denser on bands on elytra; basal region of elytra slightly rugose, with no elevated longitudinal stria; anterior pronotal tubercles absent; longitudinal median carina of ventrite 5 with three or four longitudinal teeth. ( Figure 4 )........ Balgus eschscholtzi

- Body cylindrical; body covered with dense pubescense; basal region of the elytra with five elevated longitudinal stria and without tranversal rugosities; anterior pronotal tubercles present; longitudinal median carina of ventrite 5 with one longitudinal tooth. ( Figure 7 )......................................................................... Balgus rugosus

6. Apical third of the elytra light brown or yellow, with a large black band on the basal two thirds of the elytra............. 7

- Apical third of the elytra dark brown to black, and may have various yellow or light brown bands, apex always black...... 8

7. Obconical body; elytral apex subrounded; ventrite 5 pentagonal, without longitudinal median carina; longitudinal median anterior depression of head continues posteriorly on a longitudinal groove on the vertex, not V-shaped. ( Figure 6 )................................................................................................... Balgus obconicus

- Subcylindrical body; elytral apex subacuminate; ventrite 5 triangular, with longitudinal median carina; longitudinal median anterior depression of head continues posteriorly on a longitudinal groove on the vertex, V-shaped. ( Figure 5 )..................................................................................................... Balgus humilis

8. Ventrite 5 with sinuous margins; strongly serrate; abruptly narrowed from base to the apex, which is abruptly truncated and curved; longitudinal median carina of the ventrite 5 with two or three longitudinal teeth; pronotum not abruptly attenuate at the anterior third; elytra with subacuminate apex, not narrowed abruptly. ( Figures 1 , 9 )................. Balgus tuberculosus

- Ventrite 5 without sinuous margins; slightly serrate; abruptly narrowed from base to the apex, which is truncated and not curved; longitudinal median carina of the ventrite 5 with two longitudinal teeth; pronotum abruptly attenuate at the anterior third; elytra with subacuminate apex, abruptly narrowed. ( Figure 3 )............................... Balgus eganensis

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 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.