Aegidium Westwood, 1845

Frolov, Andrey V., Akhmetova, Lilia A. & Vaz-de-Mello, Fernando Z., 2017, Revision of the mainland species of the Neotropical genus Aegidium Westwood (Coleoptera: Scarabaeidae: Orphninae), Journal of Natural History 51 (19 - 20), pp. 1035-1090 : 1038-1043

Aegidium Westwood, 1845

Aegidium Westwood 1845: 158

Type species: Aegidium colombianum Westwood, 1845 (designated by Paulian (1984)).

Aegidium: Lacordaire 1856: 130 , Gemminger and Harold 1869: 1073, Preudhomme de Borre 1886: 24, Bates 1887: 105, Arrow 1903: 515, 1904: 724, 1912: 31, Heyne and Taschenberg 1907: 72, Schmidt 1913: 61, Vulcano, Pereira and Martinez 1966: 252, Chalumeau 1977: 77, Paulian 1984: 70, Colby 2009: 1, Rojkoff and Frolov 2017: 354.

Description

Aegidium comprises medium-sized beetles (body length 10–20 mm), brown to black coloured, without pattern. Mandibles subsymmetrical, protruding past anterior margin of frontoclypeus in dorsal view. Frontoclypeus without tubercles, horns or ridges. Pronotum of males with deep excavation in the middle, with 2 horns or ridges bordering the excavation near anterior margin (lateral pronotal processes), and with a tubercle or small horn medially on the anterior margin (anterior pronotal process); these characters are subject to allometric variability and may not be developed in some males. Females have a convex pronotum without armature. Propleurae with carinae separating anterolateral areas from basal area. Scutellum narrowly rounded apically, about 1/10 length of elytra. Elytra convex, with marked humeral umbones (except for brachypterous species) and 2 low ridges in basal half; the ridges may be more or less convex, smooth, or almost indistinct. Wings fully developed or vestigial. Metepisternon triangular, its posterior angle rounded to triangular and situated in a distinct concavity of epipleuron. Mesocoxal cavities connected by a hole. Protibiae with 3 strong outer teeth in both sexes and with a smaller, medial tooth in majority of males. Mesotibiae with a tuft of setae ventroapically in males of some species. Phallobase tube-shaped, with strongly sclerotised ventral side but without differentiation of ventral and dorsal sclerites. Parameres relatively long, apices tapering or curved downwards, without setae; 2 species have complex, feeble sclerotised processes on the parameres lateroapically. Spiculum gastrale T- or Y-shaped, with relatively slender apical part. Subcoxites oval, with dense, long setae mediabasally; coxites triangular, long, with dense short setae mediabasally and sparse long setae apically; stili distinct, elongated ( Frolov 2012, figs 1 and 3).

Aegidium is apparently closely related to Onorius Frolov et Vaz-de-Mello, but can be separated by the prominent mandibles and labrum and by the slender and sparsely punctate tarsi. Putative relationships of Aegidium and West African Stenosternus Karsch ( Frolov 2013) were not supported by subsequent findings ( Frolov and Akhmetova 2015).

Diagnostic characters of species

The most reliable diagnostic character of Aegidium species is the shape of the parameres, although the differences between some species may be feeble indicating their close relationships and probably subspecific rather than specific rank (e.g. Ae. cribratum Bates, Ae. asperatum Preudhomme de Borre and Ae. minor Paulian ). Other diagnostic characters include the shape of the pronotal processes in males, dorsal sculpture of the pronotum, shape of the frontoclypeus and development of the wings (macropterous vs brachypterous). The punctation of the mesepimera and metepisterna, used by Paulian (1984) to separate species, proved an unreliable diagnostic character. We found that the shape of the spiculum gastrale varied considerably and is apparently specific for closely related species. We also found a character of sexual dimorphism that was not recorded in the Orphninae so far: the presence of a tuft of setae on the inner side of the mesotibia in males of a number of species. Setation of the tibiae is sexually dimorphic in different scarab beetle taxa, for example in some Sarophorus Erichson ( Frolov and Scholtz 2003) and Aphodius Hellwig ( Frolov 1996; Král 1997) species, and is apparently highly homoplastic in the Scarabaeidae , but in the studied cases it does not vary within the species and is a reliable diagnostic character.

Species composition and distribution

Aegidium is the most speciose genus of the Aegidiini and is widely distributed in the Neotropics. The mainland members of the genus occur in Central America (three species), the Andes (11 species), Amazonia (three species), and in the Atlantic Forest Ecoregion (one species).

Key to Aegidium species (males)

1. Apical elytral umbones well developed ( Figure 4 (a)), macropterous species ......... 2

– Apical elytral umbones indistinct ( Figure 1 (a,c)), brachypterous species....................... .............................. Aegidium angustum Frolov, Akhmetova and Vaz-de-Mello, sp. nov.

2. Endophallus with 2 strongly sclerotised, hook-shaped sclerites ( Figure 2 (b))............. ................................................................................................ Aegidium columbianum Westwood

– Endophallus without 2 strongly sclerotised hook-shaped sclerites ( Figure 4 (e))... 3

3. Mesotibiae with a tuft of setae on inner side apically ( Figures 4 (c) and 6(c))........ 4

– Mesotibiae without a tuft of setae on inner side apically ( Figures 8 (d)) and 20(c)) 7

4. Pronotum granulate at sides.............................................................................................................. ...................................... Aegidium onorei Frolov, Akhmetova and Vaz-de-Mello, sp. nov.

– Pronotum not granulate ................................................................................................................. 5

5. Cranial part of spiculum gastrale wide ( Figure 5 (c)).. ... .... Aegidium borrei Paulian

– Cranial part of spiculum gastrale narrow ( Figures 6 (g) and 7(g)).. ... ... .................... 6

6. Hind angles of pronotum obtuse ( Figure 6 (a)); phallobase long, curved ( Figure 6 (e)), narrower than parameres ( Figure 6 (f)); elytral keels poorly developed, punctate ................................. Aegidium howdeni Frolov, Akhmetova and Vaz-de-Mello, sp. nov.

– Hind angles of pronotum rounded ( Figure 7 (a)); phallobase shorter, less curved ( Figure 7 (e)), as wide as parameres ( Figure 7 (f)); elytral keels distinct, smooth.......... ...................................... Aegidium rafaeli Frolov, Akhmetova and Vaz-de-Mello, sp. nov.

7. Parameres with apical processes ( Figures 8 (b,c) and 9(d,e)) .......................................... 8

– Parameres without apical processes ( Figures 10 (d,e) and 11(d,e)) ............................. 9

8. Inner apical spur of mesotibia longer than basal mesotarsomere and curved downwards ( Figure 8 (d)).................. Aegidium atlanticum Frolov, Grossi , and Vaz-de-Mello

– Inner apical spur of mesotibia shorter than basal mesotarsomere, not curved downwards...... Aegidium peruanum Frolov, Akhmetova and Vaz-de-Mello, sp. nov.

9. Parameres short, with narrow apices (in lateral view, Figure 10 (d,e))............................. ........................................... Aegidium gilli Frolov, Akhmetova and Vaz-de-Mello, sp. nov.

– Parameres longer ( Figure 13 (c,d)), if short, then apices wider ( Figure 12 (d)) ....... 10

10. Hind angles of pronotum distinctly sinuate in dorsal view ( Figure 11 (a)).................... ................................ Aegidium sinuatum Frolov, Akhmetova and Vaz-de-Mello, sp. nov.

– Hind angles of pronotum rounded to slightly angulate in dorsal view ( Figure 12 (a))........................................................................................................................................................... 11

11. Parameres with more or less distinct, transverse, sclerotised plate basoventrally ( Figure 15 (b)) ..................................................................................................................................... 12

– Parameres without distinct, transverse, sclerotised plate basoventrally ( Figure 20 (g)) .......................................................................................................................................................... 17

12. Parameres short, wider than apical part of phallobase (in dorsal view, Figure 12 (e)), rounded apically (in lateral view, ( Figure 12 (d))........................................................................ .............................. Aegidium peres fi lhoi Frolov, Akhmetova and Vaz-de-Mello, sp. nov.

– Parameres longer, as wide as apical part of phallobase (in dorsal view, Figure 13 (d)), acute apically (in lateral view, Figure 13 (c)) ............................................................... 13

13. Sides of elytra relatively sparsely punctate (punctures separated by 1.0–0.5 puncture diameter); Andes and Central America......................................................................... 14

– Sides of elytra relatively densely punctate (punctures almost adjacent); Amazonia ....................................................................................................................... Aegidium geayi Paulian

14. Dorsal side of parameres concave (in lateral view, Figure 14 (d))...................................... .................................... Aegidium bordoni Frolov, Akhmetova and Vaz-de-Mello, sp. nov

– Dorsal side of parameres straight to convex (in lateral view, Figure 15 (d)) .......... 15

15. Parameres with small sensory area apicad of lateral tooth ( Figure 15 (b,d), arrowed) ...................................................................................................................... Aegidium minor Paulian

– Parameres without sensory area apicad of lateral tooth ( Figure 16 (c))................... 16

16. Punctation of elytra denser ( Figure 16 (a,b))................................................................................ ............................................................................ Aegidium asperatum Preudhomme de Borre

– Punctation of elytra sparser ( Figures 17 (a) and 18(a))...... Aegidium cribratum Bates

17. Parameres with smaller, rounded, feebly sclerotised apices, without lateral teeth ( Figure 19 (d,e))...................................................... Aegidium reichei Preudhomme de Borre

– Parameres with larger, somewhat rectangular, strongly sclerotised apices, with ventrolateral teeth ( Figure 20 (e,f))................................................................................................... .................................... Aegidium varians Frolov, Akhmetova and Vaz-de-Mello, sp. nov.

Figures

Figure 1. Aegidium angustum, holotype male (a,b, d, e,f), paratype female (c). Habitus in dorsal view (a, c), labels (b), aedeagus in lateral view (d), parameres in dorsal view (e), spiculum gastrale (f), locality map (g).

Figure 2. Aegidium colombianum, lectotype male (a, d, e), female (c). Habitus in dorsal view (a, c), endophallus (b), aedeagus in lateral view (d), parameres in dorsal view (e), spiculum gastrale (f), locality map (g).

Figure 4. Aegidium onorei, holotype male (a, e–i), paratype female (d). Habitus in dorsal view (a, d), labels (b), apex of metatibiae (c), endophallus (e), aedeagus in lateral view (g), parameres in dorsal view (h), parameres in ventral view (i), spiculum gastrale (f), locality map (j).

Figure 5. Aegidium borrei, holotype male. Habitus in dorsal view (a), apex of metatibiae (b), spiculum gastrale (c), locality map (d).

Figure 6. Aegidium howdeni, holotype male (a, c, g), paratype male (e, f), paratype female (d). Habitus in dorsal view (a, d), labels (b), apex of metatibiae (c), aedeagus in lateral view (e), parameres in dorsal view (f), spiculum gastrale (g), locality map (h).

Figure 7. Aegidium rafaeli, holotype male (a, c, e–g), paratype female (d). Habitus in dorsal view (a, d), labels (b), apex of metatibiae (c), aedeagus in lateral view (e), parameres in dorsal view (f), spiculum gastrale (g), locality map (h).

Figure 8. Aegidium atlanticum, holotype male. Habitus in dorsal view (a), parameres in dorsal view (b), aedeagus in lateral view (c), apex of metatibiae (d), locality map (e).

Figure 10. Aegidium gilli, holotype male (a, b), paratype male (d–f), paratype female (c). Habitus in dorsal view (a, c), labels (b), aedeagus in lateral view (d), parameres in dorsal view (e), spiculum gastrale (f), locality map (g).

Figure 11. Aegidium sinuatum, holotype male (a, b, d–f), paratype female (c). Habitus in dorsal view (a, c), labels (b), aedeagus in lateral view (d), parameres in dorsal view (e), spiculum gastrale (f), locality map (g).

Figure 12. Aegidium peresfilhoi, holotype male. Habitus in dorsal view (a), labels (b), spiculum gastrale (c), aedeagus in lateral view (d), parameres in dorsal view (e), locality map (f).

Figure 13. Aegidium geayi, holotype male (a), male (c–d), female (b). Habitus in dorsal view (a, b), aedeagus in lateral view (c), parameres in dorsal view (d), spiculum gastrale (e), locality map (f).

Figure 14. Aegidium bordoni, holotype male (a, d–f), paratype female (c). Habitus in dorsal view (a, c), labels (b), aedeagus in lateral view (d), parameres in dorsal view (e), spiculum gastrale (f), locality map (g).

Figure 15. Aegidium minor, holotype male (a, d, e), male (b, f), female (c). Habitus in dorsal view (a, c), parameres in ventral view (b), aedeagus in lateral view (d), parameres in dorsal view (e), spiculum gastrale (f), locality map (g).

Figure 16. Aegidium asperatum, holotype male (a, c, d), male (b, e). Habitus in dorsal view (a, b), aedeagus in lateral view (c), parameres in dorsal view (d), spiculum gastrale (e), locality map (f).

Figure 17. Aegidium cribratum, lectotype male (a, c, d), male (e), female (b). Habitus in dorsal view (a, b), aedeagus in lateral view (c), parameres in dorsal view (d), spiculum gastrale (e), locality map (f).

Figure 19. Aegidium reichei, lectotype male (a, d, e), male (b), female (c). Habitus in dorsal view (a– c), aedeagus in lateral view (d), parameres in dorsal view (e), spiculum gastrale (f), locality map (g).

Figure 20. Aegidium onorei, holotype male (a–c, h), paratype male (d, e–g). Habitus in dorsal view (a, d), labels (b), apex of metatibiae (c), aedeagus in lateral view (e), parameres in dorsal view (f), parameres in ventral view (g), spiculum gastrale (h), locality map (i).