Brachinus Bonelli, 1810

Akhil, S. V., Divya, M. & Sabu, K. Thomas, 2020, Bombardier beetles of genus Brachinus Weber, 1801 (Carabidae: Brachininae Brachinini) from India, Zootaxa 4816 (4), pp. 576-600 : 577-578

Key to Indian species of Brachinus Bonelli, 1810

1. Elytra with spots or transverse bands...................................................................... 2

- Elytra without spots or transverse bands, monochrome black/bluish black/brownish black, only the suture sometimes reddish yellow............................................................................................. 12

2. Elytra yellow; three black markings of various shapes on elytra ( Fig. 1g )................................... B. pictus

- Elytra black/blue black/brown black; with reddish yellow spots or transverse band on elytra.......................... 3

3. Elytra with reddish yellow median transverse band and smaller triangular reddish yellow spot on the apex..... B. longipalpis

- Elytra with only reddish yellow spots, without median transverse bands.......................................... 4

4. Elytra with 6 distinct spots (3 on each elytron).............................................................. 5

- Elytra with 4 spots (2 on each elytron)..................................................................... 8

5. Head and pronotum rough, densely punctated and pubescent with closely placed setae................... B. hexagrammus

- Head and pronotum smooth, sparsely punctated, pubescent with widely spaced setae................................ 6

6. Pronotum longer than broad; elytra with reddish yellow lateral margin starting from the basal spot and continuing to apex, eventually forming an apical reddish yellow band................................................ B. sexmaculatus

- Pronotum broader than long; elytra without reddish yellow lateral margin and apical band............................ 7

7. Elytral apex forming a re-entrant angle ( Fig. 5a ), elytral basal spot large, reaching the humerus; pronotum with basal margin broadly and lateral margin narrowly brownish black................................................. B. eucosmus

- Elytral apex rounded without forming a re-entrant angle ( Fig. 5b ), elytral basal spot small, not reaching the humerus; pronotum with apical, basal and lateral margins broadly black...................................................... B. reyi

8. Pronotal apical margin with anterior lateral projection ( Fig.5c )................................................. 9

- Pronotal apical margin without anterior lateral projection ( Fig.5d )......................................... B. charis

9. Elytra with reddish yellow lateral margin................................................................. 10

- Elytra without reddish yellow lateral margin............................................................... 11

10. Pronotum densely punctated, pubescent with closely placed setae......................................... B. illotus

- Pronotum glabrous........................................................................... B. tetracolon

11. First spot on elytra aligned towards base, elytral apex not forming re-entrant angle ( Fig. 5b )................... B. geiseri

- First spot on elytra placed in the midregion, elytral apex forming a strong re-entrant angle ( Fig. 5a )........ B. tetragrammus

12. Elytra unicoloured; suture same colour as the elytra......................................................... 13

- Elytra bicoloured; suture reddish yellow.................................................................. 21

13. Head with two reddish yellow spots on frons.................................................. B. andamanensis

- Head concoloured, without spots........................................................................ 14

14. Elytra blue-black............................................................................ B. pallidipes

- Elytra pitch black/pitch brown.......................................................................... 15

15. Pronotum and elytra punctated, pubescent................................................................. 16

- Pronotum and elytra smooth, glabrous........................................................ B. chaudoirianus

16. Antennal segment 3 subequal to segments 1 and 2 combined.................................................. 17

- Antennal segment 3 shorter than segments 1 and 2 combined.................................................. 20

17. Pronotum concoloured................................................................................ 18

- Pronotum bi-coloured................................................................................. 19

18. Pronotum dark brownish black with deep median groove deep, reaching the basal and apical margins; elytral apex rounded, not forming a re-entrant angle ( Fig. 5b )................................................................ B. hazardi

- Pronotum reddish yellow with median groove shallow, not reaching the basal and apical margins; elytral apex straight, forming a re-entrant angle ( Fig. 5a )......................................................................... B. inops

19. Pronotum with acute posterior angles ( Fig. 5c, 5e ), basal margin broadly brownish black; elytra convex........... B. dryas

- Pronotum with obtuse hind angles ( Fig. 5d ), both lateral and basal margins broadly brownish black; elytra subparallel............................................................................................... B. limbicollis

20. Pronotum rugose, punctate, median groove shallow; elytral striations weak............................... B. sordidus

- Pronotum smooth, sparsely punctate, median groove deep; elytral striations deep................ B. devagiriensis sp. nov.

21. Elytral sutural line with narrow reddish yellow colouration................................................... 22

- Elytral sutural line with broad reddish yellow colouration.................................................... 23

22. Antennal segment 3 subequal to segment 1 and 2 combined; pronotum longer than broad, median furrow deep, reaching the basal and apical margins; elytral apex forming faint re-entrant angle ( Fig. 5a ) with broad membranous border...................................................................................................... B. flaviventris

- Antennal segment 3 shorter than segment 1 and 2 combined; pronotum wider than long, median furrow shallow, not reaching the basal and apical margins; elytral apex not forming a re-entrant angle ( Fig. 5b ) but with a narrow membranous border................................................................................................ B. vigilans

23. Elytra with reddish yellow lateral margins................................................................. 24

- Elytra without reddish yellow lateral margins.............................................................. 27

24. Antennal segments 1–2 reddish yellow, remainder brownish, segment 3 subequal to segments 1 and 2 combined......... 25

- Antennal segments 1–4 reddish yellow, remainder brownish, segment 3 shorter than segments 1 and 2 combined........ 26

25. Elytra brownish black.......................................................................... B. limbellus

- Elytra black................................................................................. B. cinctellus

26. Pronotum length equal to width, base straight................................................... B. pokharaensis

- Pronotum longer than broad, base bisinuate.......................................................... B. stevensi

27. Pronotum with hind angles pointed, at right angles ( Fig. 5f )........................................... B. suturellus

- Pronotum with hind angles blunt, obtuse ( Fig. 5d ).......................................................... 28

28. Pronotum disc with posterior fourth parallel, hind angles slightly obtuse.................................. B. peltastes

- Pronotum disc with posterior fourth divergent, hind angles very obtuse.................................. B. modestus

Figures

FIGURE 1. Dorsal habitus of Indian Brachinus species: a) B. dryas Andrewes, 1936 (holotype, BMNH); b) B. inops Andrewes, 1932 (holotype, BMNH); c) B. hexagrammus Chaudoir, 1876 (syntype, MNHN); d) B. sexmaculatus Dejean, 1825 (syntype, MNHN); e) B. tetracolon Chuadoir, 1876 (syntype, MNHN); f) B. tetragrammus Chaudoir, 1876 (syntype, MNHN); g) B. pictus (Hope, 1833) (ZSIM); h) B. cinctellus Chaudoir, 1876 (syntype, MNHN); i) B. eucosmus Andrewes, 1937 (holotype, BMNH)

FIGURE 5. Morphological features of Brachinus: a) Elytral apex forming re-entrant angle; b) Elytral apex not forming a reentrant angle; c) Pronotum with apical margin having anterior projection on lateral sides, hind angles slightly acute; d) Pronotal apical margin without anterior projection on lateral sides, hind angles obtuse; e) Pronotum with hind angles acute; f) Pronotum with hind angle at right angles.