Gromphas lemoinei Waterhouse, 1891, Waterhouse, 1891
Cupello, Mario & Vaz-De-Mello, Fernando Z., 2013, Taxonomic revision of the South American dung beetle genus Gromphas Brullé, 1837 (Coleoptera: Scarabaeidae: Scarabaeinae: Phanaeini: Gromphadina), Zootaxa 3722 (4), pp. 439-482: 454-458
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|Gromphas lemoinei Waterhouse, 1891|
Type specimen: Holotype: undetermined sex (“ Type ”, “Caracas”, “ Gromphas lemoinei Waterh. type ”, “ Onthophoida lemoinei Reiche” “ Gromphas aeruginosa (Perty) 614: 99 ”, “ Gromphas aeruginosa Perty, 1830 det. CPDT Gillet, 2007 ”), BMNH (examined by photos [ Figs. 11 View FIGURES 11 – 12. 11 a –c]).
Type locality: “Caracas, La Guayra” (Waterhouse 1891).
Redescription: Color: Anterior region of head black; remainder of dorsum with bright and metallic reflections of green, copper, and burgundy, with some of these colors predominating or, more commonly, a mixture of all. Pygidium colored as elytra. Metasternum bright and with uniform coloring.
Head: Clypeus with two lobes at apex (in worn specimens lobes absent and apex rounded or truncate); margin between these lobes and genae rounded ( Fig. 25 View FIGURES 24 – 28 ). Margin of genae extended beyond clypeal margin ( Fig. 25 View FIGURES 24 – 28 ). Clypeus with smooth tegument adjacent to eyes; granulation gradually denser and squamous toward the outer margin ( Fig. 25 View FIGURES 24 – 28 ). Cephalic projection ranging from a low and transverse elevation arched upward to anteroposteriorly flat horn with acuminate apex; horn granulate on both faces ( Figs. 30 View FIGURES 29 – 33 a –c). Frons smooth adjacent to eyes and granulate in center ( Fig. 25 View FIGURES 24 – 28 ).
Thorax: Lateral region of pronotum with dense squamous granulation (Fig. 17); granulation always dense, without gradual decrease toward posteromedian region; posterior region with sparse granulation abruptly delimited ( Figs. 7–10 View FIGURES 7 – 10 ). Longitudinal midline with smooth and glossy tegument present at center of pronotum (easily observable in Fig. 3). Posterior pronotal fossae absent or greatly reduced only in major specimens; in other specimens, fossae present without granulation. Posterior margin of pronotum rounded.
Anterior region of pronotum with ornamentation ranging from two shallow impressions in anterior margin ( Figs. 9–10 View FIGURES 7 – 10 ) to a prominence with two wide, triangular projections; lateral margin of prominence always straight ( Figs. 7–8 View FIGURES 7 – 10 ); separation between projections always very narrow; anterior to prominence a with a pair of concavities with smooth tegument (Fig. 17).
Mesosternum with dense pilosity ( Fig. 52 View FIGURES 49 – 52 ). Metasternum very densely punctate in center. Anteromedian angle of metasternum flat and with rounded apex ( Fig. 52 View FIGURES 49 – 52 ), area in front of angle with evident setae (Figs. 16, 52).
Legs: Protibiae very broad in both sexes; in ventral view, longitudinal carina simple in both sexes ( Fig. 22 View FIGURES 21 – 23 ). Protibial spur with apex slightly bent laterally and downward ( Figs. 22 View FIGURES 21 – 23 , 46 View FIGURES 34 – 48. 34 ); inner apical protibial angle with a tuft of long setae in both sexes ( Fig. 22 View FIGURES 21 – 23 ). Apical protarsomere tapered and only slightly elongate at apex ( Figs. 22 View FIGURES 21 – 23 , 46 View FIGURES 34 – 48. 34 ). Metatibiae very broad and robust ( Fig. 41 View FIGURES 34 – 48. 34 ). Mesotarsi and metatarsi not particularly enlarged and with apical tarsomeres slightly curved apically ( Fig. 48 View FIGURES 34 – 48. 34 ). Metatibial spur with apex distinctly curved ( Fig. 39 View FIGURES 34 – 48. 34 ).
Elytra: Striae very fine and, especially those more medial, carinulate from base to no more than midlength of elytra, where they become simple ( Fig. 37 View FIGURES 34 – 48. 34 ); interstriae, especially mesial, slightly convex, producing a grooved appearance of striae to the naked eyes. Sutural margin densely punctate.
Abdomen: Pygidium flat, not margined basally ( Fig. 36 View FIGURES 34 – 48. 34 ). Groove of propygidium extending to base of pygidium. Abdominal sternites sparsely punctate.
Aedeagus: Phallobase in ventral view with a very narrow apical membranous area ( Fig. 53 View FIGURES 53 – 56 c). Medial sclerite wide, flat and strongly curved laterally ( Fig. 58 View FIGURES 57 – 62 ).
Measurements: Males (10 specimens): TL: AV: 16; MX: 20.1; MN: 12.7; SD: 2.04. PL: AV: 13.07; MX: 17; MN: 10.3; SD: 1.9. PW: AV: 9.4; MX: 11.7; MN: 7.1; SD: 1.29. PP: AV: 2.51; MX: 3.8; MN: 1.4; SD: 0.40. Females (4 specimens): TL: AV: 17.3; MX: 19.2; MN: 13.9; SD: 2.09. PL: AV: 13.73; MX: 14.8; MN: 11.2; SD: 0.9. PW: AV: 9.78; MX: 10.4; MN: 8.3; SD: 0.63. PP: AV: 2.63; MX: 3.1; MN: 2.1; SD: 0.46. Total (14 specimens): TL: AV: 16.38; SD: 2.06. PL: AV: 13.25; SD: 1.68. PW: AV: 9.5; SD: 1.14. PP: AV: 2.54; SD: 0.62.
Intraspecific variation and taxonomic discussion: The closest relative of G. lemoinei is G. aeruginosa , with which it was synonymized for more than a century. The description given by Waterhouse (1891), although short and based only on a single specimen, is very accurate and uses basically the same morphological features used by us to distinguish these two species; it is surprising, therefore, that this synonymy has remained for so long. Gillet (1911) was the first author to mention Waterhouse’s species as “ var. lemoinei ” of G. aeruginosa , not making clear, however, whether or not he considered them synonymous; d’Olsoufieff (1924) was the first to state unequivocally this synonymy. Nevertheless, neither of these two authors nor even Barattini & Saénz (1960, 1964) discussed or justified this synonymy or the condition of variety of G. lemoinei , and it is very likely that they have not seen the type specimens. All this confusion probably occurred simply because of the superficial similarity that these two species show at the first glance; as they share only between themselves the following characteristics: genae and frons smooth adjacent to eyes ( Figs. 24–25 View FIGURES 24 – 28 ); cephalic projection very high ( Figs. 29–30 View FIGURES 29 – 33 ); pronotum with a smooth midlongitudinal line; presence of pronotal prominence (Figs. 1 –5, 7– 10); flattened anteromedian angle of metasternum ( Fig. 52 View FIGURES 49 – 52 ); tibiae very broad in both sexes ( Fig. 22 View FIGURES 21 – 23 ); protibia with ventral carina simple in both sexes and with apical tuft of setae without apparent sexual dimorphism ( Fig. 22 View FIGURES 21 – 23 ); protibial spur only slightly curved at apex ( Figs. 22 View FIGURES 21 – 23 , 46 View FIGURES 34 – 48. 34 ); elytral striae carinulae extending at most only to midlenght of elytron ( Fig. 37 View FIGURES 34 – 48. 34 ); and phallobase with a narrow apical membranous area ( Fig. 53 View FIGURES 53 – 56 c). Despite this extensive list of similarities, several morphological and biogeographical differences convincingly demonstrate the validity of each of these two species.
Morrone (2001, 2006) recognized four subregions of the Neotropical region (Caribbean, Amazonian, Chacoan, and Parana), each them divided into several provinces. Gromphas lemoinei and G. aeruginosa inhabit northern South America, but have widely separated distributions. The former species occurs in the Venezuelan Coast and Venezuelan Llanos provinces of the Caribbean subregion, while the latter species is widely distributed in eight provinces of the Amazonian subregion and in the north of Chaco province of Chacoan subregion. Nowhere are these two species found in sympatry; in fact, they are separated by large physiographic barriers such as the Guiana Shield and the Orinoco River. This geographical separation certainly has contributed to the emergence and maintenance of the morphological distinction between them.
The main distinction in the external morphology between G. aeruginosa and G. lemoinei is in the shape of the pronotal prominence of well-developed specimens: each of the two projections of the prominence of G. aeruginosa is clearly thin and tapered, while the projections are wide and triangular in G. lemoinei . In general, the projections are strongly divergent in G. aeruginosa , and always subparallel in G. lemoinei ; hence the lateral margins of the prominence are usually curved in G. aeruginosa (Fig. 1), while in G. lemoinei they are always straight ( Figs. 7–8 View FIGURES 7 – 10 ). The space between the apices of the projections in G. lemoinei is much narrower than in G. aeruginosa , and the total width of the pronotal prominence is proportionally greater in G. aeruginosa than in G. lemoinei . For example, the largest specimen of G. lemoinei examined by us has a total length of 20.1 mm and a width of pronotal prominence of 3.8 mm; at the same time, the average width of the prominence in three specimens of G. aeruginosa with total length between 19.8 mm and 20.3 mm is 4.6 mm (the total average in G. aeruginosa is 2.83 mm and in G. lemoinei 2.54 mm). In a few specimens of G. aeruginosa the lateral margins of the prominence are subparallel and not strongly divergent (Fig. 2); however, in such cases, the thin and tapered projections and especially the wide separation between the projections are clear characteristics of G. aeruginosa .
Characteristics of the tegument also separate these two species. The punctation in the center of metasternum and along the sutural margin of the elytra is very sparse in G. aeruginosa and seen only in unwarn specimens; in G. lemoinei , however, this punctation is much denser and clearly evident. Regarding the pronotal granulation, in G. aeruginosa , the squamous granules of the lateral region become progressively finer and sparser toward the center of the pronotum; in G. lemoinei , on the other hand, the density of granulation is always very high across the pronotum, except within the smooth anterior concavities and along the midline. The presence of posterior pronotal fossae also distinguish these two species: in G. lemoinei , larger specimens have no trace of these fossae, which are apparent in smaller specimens; in G. aeruginosa , the fossae are always present regardless of specimen size.
The elytral striae are also distinct: in G. aeruginosa , the interstriae are flat and in the same plane as the striae, whereas in G. lemoinei the interstriae, especially the more mesial ones, are slightly convex at the base and the striae appear furrowed to the naked eye. This furrowed appearance gives the impression of a more elongate elytra in G. lemoinei than in G. aeruginosa .
More developed specimens of G. aeruginosa have the cephalic projection distinctly notched and bifid ( Fig. 29 View FIGURES 29 – 33 b) (round or truncate in worn specimens [ Fig. 29 View FIGURES 29 – 33 c]). In large G. lemoinei , on the other hand, the cephalic projection is always acuminate ( Fig. 30 View FIGURES 29 – 33 ). While one could argue that the lack of notch in specimens of G. lemoinei has resulted from wear, even the best preserved specimens of G. lemoinei have no trace of an incision and no worn G. aeruginosa has the projection acuminate, thus ruling out this possibility. A very large Bolivian specimen of G. aeruginosa shows the cephalic projection extremely broad in a way not seen in any other specimen ( Fig. 29 View FIGURES 29 – 33 a).
Finally, there is a difference between these two species also in the medial sclerite. While in G. aeruginosa the curvature is mainly downwards ( Fig. 57 View FIGURES 57 – 62 ), in G. lemoinei this sclerite is flatter, wider and very much more strongly curved to the side ( Fig. 58 View FIGURES 57 – 62 ). However, these two forms are clearly more similar to each other than to the other species of Gromphas .
Comments: The presence of G. lemoinei in San Fernando de Apure is inferred from the geographic distribution of G. aeruginosa presented by Barattini & Saénz (1960, 1964). These authors regarded the latter species (which does not occur in Venezuela) as a senior synonym of the former, but it is likely that these data refer to G. lemoinei .
Bionomics: Noriega (2002) found five specimens of G. lemoinei (cited as G. aeruginosa ) on the floodplain of Rio Duda, La Macarena, Meta, Colombia; the only other species of Scarabaeinae found by him in this place was Sulcophanaeus leander (Waterhouse, 1891) . According Noriega (personal communication) these two species share the same activity time and the same food resource. As G. lemoinei is found only in savannas, open areas and river sandbanks and never enter in the forest, it is possible that this species use the rivers and their banks as corridors from the savannas of the Llanos Orientales to inside Amazon region in Colombia (Noriega, personal communication). Noriega also reported that all specimens collected by him were associated with cattle ( Bos indicus Linnaeus, 1758 ), capybara ( Hydrochoerus hydrochaeris (Linnaeus, 1766 )) , or crocodile ( Crocodylus intermedius Graves, 1819 ) dung.
Based on the specimens examined in this study, G. lemoinei seems to be active throughout the year, as is G. aeruginosa . The recorded months are January, March, June, July, September, November, and December.
Geographical distribution: Caribbean subregion: Venezuelan Coast and Venezuelan Llanos. COLOMBIA: Arauca: Arauca. Meta: La Macarena, Puerto Gaitan, San Martín, Villavicencio. Guaviare: San José del Guaviare. VENEZUELA: Distrito Capital: Caracas. Barinas: Andrés Eloy Blanco (El Cantón), Ezequiel Zamora (San Antonio de Pagen). Táchira: Libertador (San Joaquín de Navay), San Cristóbal, Santo Domingo. Apure: San Fernando de Apure. ( Fig. 66 View FIGURE 66 ).
Material examined: 17 males and 10 females. COLOMBIA: ARAUCA: Arauca, 120 m., IX. 2005, Jorge Ari Noriega col.— 1 male (CJAN). GUAVIARE: San Jose del Guaviare, sabana, IX. 2000, J. Noriega col.— 2 males (CJAN). META: La Macarena, CIEM, Playa del Rio Duda, 350 m, XII. 1995, Jorge A. Noriega col.— 2 females (CJAN); La Macarena, CIEM, I. 1998, J. Noriega col.— 1 male (CJAN); Puerto Gaitan, 150 m., X. 2001, Jorge Ari Noriega col.— 1 female (CJAN); San Martín, 350m., VII. 2007, Jorge Ari Noriega col.— 1 male and 1 female (CJAN); Villavicencio, 13.XII. 1994, Oscar Gómez col.— 1 female (CEMT). VENEZUELA: BARINAS: Andrés Eloy Blanco, El Cantón, XI. 1983, C. Borges col.— 1 male (MIZA); Ezequiel Zamora, San Antonio de Pagen, VII. 1989, without collector— 1 female (MZSP) and 2 males (CEMT); San Antonio, VII. 2007, J. Noriega col.— 1 male and 1 female (CJAN). DISTRITO CAPITAL: Caracas, 1905, Fry col.— 1 male (BMNH). TÁCHIRA: Libertador, San Joaquín de Navay, 100 m, 24.III. 1989, D. Havranek col.— 1 male (CMNC); San Cristóbal, without date and collector— 2 male (MIZA); San Cristóbal, 17.III. 1980, without collector— 1 male (MIZA); Santo Domingo, Hacienda Santa Rosa, VI. 1992, J. Blanco col.— 1 male (MZSP) and 2 male and 2 female (CEMT).
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