Discodon tricolor
Creators: name: Biffi, Gabriel
name: Geiser, Michael
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Cantharidae
Discodon
Discodon tricolor

description: Key to the species of D. tricolor mimetic complex
Several species in different beetle families from the Atlantic Forest biome in Brazil show a similar colour pattern with a black body and elytra, a pronotum with orange lateral margins, and white to orangish elytral spots (Fig. 17). This identification key distinguishes cantharid species with such a colour pattern, as well as similar species with entirely black elytra. Included in the key is the cantharid species Chauliognathus fenestratus (Perty, 1830) (Fig. 17A) which, despite belonging to a different subfamily (Chauliognathinae), is sympatric and may easily be confounded with species of D. tricolor mimetic complex.
1. Fronto-clypeal suture distinct; anterior and lateral margins of pronotum broadly arched; tibial spurs absent; tarsal claws always simple; last ventrite broad and strongly convex in males and flat and with a median parallel-sided notch in females (Chauliognathinae, Chauliognathus) ................................ .......................................................................................... Chauliognathus fenestratus (Perty, 1830)
– Fronto-clypeal suture indistinct; lateral margins of pronotum slightly sinuous, males with a notch at posterior third (Figs 7–8); tibial spurs present (Fig. 9L); anterior prothoracic tarsal claws lobed basally (Fig. 9A–K), posterior claws on meso- and metathoracic tarsal claws apparently split at the apex; last ventrite deeply divided into two halves in males (Fig. 10), and entire, sometimes with median projections in females (Fig. 15) (Silinae, Discodon) ........................................................... 2
2. Elytra with white or yellowish spots ................................................................................................ 3
– Elytra entirely black ........................................................................................................................ 12
3. Elytra with small and weakly defined rounded spots, legs reddish brown (Fig. 4D, F) ..................... ....................................................................................................................... D. testaceipes Pic, 1930
– Elytral spots large, legs entirely black .............................................................................................. 4
4. Antennae mostly black with some antennomeres clearer, or antennae mostly testaceous to light brown ................................................................................................................................................ 5
– Antennae entirely dark brown or black ............................................................................................ 7
5. Males: lobe of protarsal claws sinuate (Fig. 9A–D); aedeagus: ventral wall of tegmen short and broad, distal margin with two rounded lobes and a median notch (Fig. 11). Females: distal margin of last ventrite sinuate, with short median projection (Fig. 15A–C) ..................................................... 6
– Males: lobe of protarsal claws broadly rounded (Fig. 9J); aedeagus (Fig. 13D–F): ventral wall of tegmen elongate, distal margin slightly concave medially. Females: distal margin of last ventrite broadly arched, without projections or notches (Fig. 15J) ..................... D. viridimontanum sp. nov.
6. Antennae mostly pale yellow to testaceous brown, except antennomere I or I and II. Males: lobe of protarsal claws slightly sinuate (Fig. 9A); aedeagus (Fig. 11A): ventral wall of tegmen longer, median lobe with a narrow central sclerite. Females: last ventrite with distal margin almost straight, with a slight median projection (Fig. 15A) .............................. D. tricolor (Guérin-Méneville, 1832)
– Antennae with last two or three antennomeres orange to light brown. Males: lobe of protarsal claws with a distinctly projecting lobule (Fig. 9C); aedeagus (Fig. 11G–I): ventral wall of tegmen less distinctly narrowed laterally, central sclerite of median lobe broader. Females: last ventrite with distal margin sinuate (Fig. 15C) ............................................................................. D. vanini sp. nov.
7. Elytra with weakly defined costae, more visible anteriorly (Fig. 3D); elytral spots rounded, dark yellow to orangish; antennae without lines ............................................. D. aurimaculatum sp. nov.
– Elytra smooth, without costae; elytral spots variable; antennae with or without lines ..................... 8
8. Pronotum black with dark reddish-brown markings at the angles (Fig. 7G) ...................................... ...................................................................................................................... D. marginicolle sp. nov.
– Pronotum with a broad longitudinal black band with irregular yellow and orange markings at the sides .................................................................................................................................................. 9
9. Pronotum distinctly narrower than humeri, about 1.3 times as wide as long (Fig. 7K). Males: hind leg strongly modified, coxa with unciform projection, femur swollen and tibia flattened distally (Fig. 9L); antennomeres VIII–XI with antennal lines (Fig. 6K); lobe of protarsal claws with broadly rounded margin (Fig. 9K); last ventrite broad, inner margins of halves notched, divergent, exposing the aedeagus (Fig. 10K); aedeagus with ventral wall of tegmen with a long median projection (Fig. 13G–J) ............................................................................................. D. crassipes Wittmer, 1952
– Pronotum wider, nearly or as wide as humeri. Males: hind leg slender, not modified; antennomeres with or without antennal lines ......................................................................................................... 10
10. Elytral spots somewhat triangular, elongate, extending anteriorly and posteriorly (Fig. 3A). Males: antennomeres without antennal lines (Fig. 6B); lobe of protarsal claws with sinuate margin (Fig. 9B); last ventrite elongate, inner margins of halves nearly parallel (Fig. 10B); aedeagus with ventral wall of tegmen short and broad, distal margin with a pair of rounded lobes and a median incision (Fig. 11D–F). Females: distal margin of last ventrite sinuous, with a short projection medially (Fig. 15B) .................................................................................................... D. neoteutonum sp. nov.
– Elytral spots smaller and rounder. Males: antennomeres with or without antennal lines; aedeagus elongate, distal margin of ventral wall of tegmen greatly projected. Females: distal margin of last ventrite with a pair of projections and a median V- ou U-shaped incision (Fig. 15E–F, H–I) ........11
11. Males: antennomeres without antennal lines (Fig. 6I); last ventrite elongate, distal margins of halves truncate, inner margins broadly separated, exposing part of aedeagus and meeting distally (Fig. 10I); aedeagus: distal margin of ventral wall of tegmen triangular, with an acute apex (Fig. 13A–C). Females: distal margin of last ventrite with two short projections and a median V-shaped notch (Fig. 15I) ................................................................................................................ D. tamoio sp. nov.
– Males: antennomeres IX–XI with antennal lines (Fig. 6E); last ventrite broad, distal margins of halves rounded, inner margins almost parallel (Fig. 10E); aedeagus: distal margin of ventral wall of tegmen with a pair of short and truncate projections, and a very long and curved median projection (Fig. 12A–C). Females: distal margin of last ventrite with two long projections and a median U-shaped notch (Fig. 15E) ............................................................................ D. lineaticorne sp. nov.
12. Antennae mostly orangish to light brown; head much narrower than pronotum, eyes prominent ..... ......................................................................................................................................................... 13
– Antennae dark brown to black; head broad, nearly as wide as the pronotum (Fig. 5E–F); eyes not prominent .............................................................................................. D. nigrocephalum Pic, 1949
13. Elytra narrower, nearly parallel, with weakly defined costulae (Fig. 5D); pronotum transverse, anterior margin nearly straight (Fig. 7H); antennae black at the base, clearing towards the apex; aedeagus elongate, distal margin of ventral wall of tegmen with a flat median projection and lateral sinuous lobes (Fig. 12J–M). Females: distal margin of last ventrite with two long projections and a median U-shaped notch (Fig. 15H) .......................................................... D. tenuecostatum sp. nov.
– Elytra wider, rough, without weakly defined costulae (Fig. 5A); pronotum with anterior and lateral margins broadly arched (Fig. 7D); antennae mostly light brown to orangish; aedeagus short, distal margin of ventral wall of tegmen with a median incision (Fig. 11J–L). Females: last ventrite short, distal margin sinuous, not strongly projected posteriorly (Fig. 15D) ................................................. ......................................................................................................... D. obscurior Pic, 1906 stat. nov.
description: Published as part of Biffi, Gabriel & Geiser, Michael, 2022, A revision of Discodon tricolor (Guérin-Méneville) and its mimics from the Atlantic forests of Brazil (Coleoptera: Cantharidae), pp. 148-189 in European Journal of Taxonomy 834 (1) on pages 181-183, DOI: 10.5852/ejt.2022.834.1907, http://zenodo.org/record/7017677