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Una nueva especie del genero sudamericano Metachaetodus (Coleoptera: Scarabaeoidea: Hybosoridae: Hybosorinae).

A new species of the South American genus Metachaetodus (Coleoptera: Scarabaeoidea: Hybosoridae: Hybosorinae)


The genus Metachaetodus was described by De Borre (1886) for two species: D. discus De Borre (type species) from Argentina and Uruguay and M. brunneicollis De Borre from Argentina (De Borre, 1886; Allsopp, 1984; Ocampo & Ballerio, 2006). Schmidt (1913) provided a short reference to the genus without providing further details on these species. Many years after that, Martinez (1994) refers to Metachaetodus and briefly discussed its systematic relationships, suggesting that this genus is closer to Coilodes Westwood, Apalonychus Westwood, and Hapalonychoides Martinez (Hybosorinae) than it is to Chaetodus Westwood (Anaidinae) as it was originally proposed by De Borre (1886). The latter hypothesis was supported by Ocampo & Hawks (2006) in a phylogenetic analysis of the family Hybosoridae. In his contribution, Martinez (1994) also indicated that M. discus and M. brunneicollis are probably color variations of the same species, but he preferred to keep them as different species.

As a result of a survey and inventory of the scarab fauna of the Chacoan region in Northern Argentina, a new species of Metachaetodus was found and it is described here as part of my continuous work on the New World hybosorid fauna. The purpose of this contribution is to describe the new species of Metachaetodus, provide a key and diagnostic characters for the three species of the genus, and summarize what it is known about their distribution including a new country record for Brazil.


Body measurements, puncture density and size, and density of setae are based on the following standards. Body length was measured from the anterior margin of the pronotum (at the middle) to the apex of the elytra. Body width was measured across the elytra at the widest point. Puncture density was considered "dense" if punctures were nearly confluent to less than two puncture diameters apart, "moderately dense" if punctures were two to six diameters apart, and "sparse" if punctures were more than six diameters apart. Puncture size was defined as "small" if punctures were 0.02 mm or smaller, "moderate" if 0.02-0.07 mm, and "large" if 0.07 mm or larger. Setae were defined as "sparse" if there were few setae, "moderately dense" if the surface was visible but with many setae, and "dense" if the surface was not visible through the setae. Elytral carinae were counted from the elytral suture, with the elytral suture included. Holotype specimen label data was copied verbatim using "/" between the lines of the labels.

This study was based on specimens from the following institutions (with curators given in brackets):

CMNC--Canadian Museum of Nature, Ottawa, Canada (R. S. Anderson, F. Genier).

CNCI--Canadian National Collection of Insects, Ottawa, Canada (Y. Bousquet)

FMNH--Field Museum of Natural History, Chicago, USA (A. Newton, M. Thayer)

IADIZA--Coleccion del Laboratorio de Entomologia (CEI), Instituto Argentino de Investigaciones de las Zonas Aridas, Mendoza, Argentina (F. C. Ocampo).

UNSM--University of Nebraska State Museum, Lincoln, Nebraska, USA (B. C. Ratcliffe).


Metachaetodus De Borre, 1886

Metachaetodus De Borre, 1886: 118.

Type species: Metachaetodus discus De Borre, 1886 (original designation).

Diagnosis. Hybosorid genus that can be recognized from all other New World genera of the family by the following combination of characters: Mandibles dorsoventrally flat, broadly rounded, lacking dorsal teeth; labrum transverse, with anterior margin slightly emarginated; antenna with nine antennomeres, antennal club with three antennomeres, basal antennomere of club cup-shaped; pronotum with lateral margins convergent toward apex; pronotal anterior angles acute and posterior angles right-angled; pronotal and elytral surface glabrous, punctate, punctures moderately dense; meso- and metatibiae with one transversal carinae, tarsal claws simple, curved; and male parameres strongly asymmetrical.

Metachaetodus brunneicollis De Borre, 1886

(Figs. 1,2, 9)

Metachaetodus brunneicollis De Borre, 1886: 119.

Diagnosis. Metachaetodus brunneicollis can be recognized from other species in the genus by the following combination of characters: Body color uniform light brown; pronotum with lateral margins smooth; elytral surface punctate lacking carinae; male genitalia as in figures 1, 2.

Distribution (Fig. 9). ARGENTINA. Cordoba: Anisacate (1), Cruz del Eje (2). La Rioja: Chepes (6 km E) (2), Quebrada del Rosillo (3). Mendoza: Nacunan (1). San Luis: El Milagro (1), La Toma (1), Quines (3).

Remarks. Aside from the differences in color that are consistent between M. discus and M. brunneicollis, I found differences in the male genitalia that justify to keep these two as separate species (Figs. 1-4), contrary to what was suggested by Martinez (1994) who probably, at that time, did not study the genitalia of Metachaetodus.


Metachaetodus discus De Borre

(Figs. 3-5, 9)

Metachaetodus discus De Borre, 1886: 118.

Diagnosis. Metachaetodus discus can be recognized from other species of the genus by the following combination of characters: Body bicolored; head, pronotum, and elytral disc brown, elytral margins light brown; pronotum with lateral margins smooth; elytral surface punctate, lacking carinae; and male genitalia as in figures 3-4.

Distribution (Fig. 9). ARGENTINA. Buenos Aires: Jose Carlos Paz (2), Felipe Sola (1), La Plata (1), Sierra de la Ventana (1). Entre Rios: Pronunciamiento (16). BRAZIL. Santa Catarina: Nova Teutonia (2). URUGUAY. Montevideo (De Borre 1886).

Metachaetodus carolineae sp. nov.

(Figs. 6-9)

Diagnosis. Metachaetodus carolineae can be recognized from other species of the genus by the following combination of characters: Body color uniformly dark brown; pronotum with lateral margins denticulate; elytra with 10 well developed, punctate carinae.

Description. Holotype Female (Figs. 6-8). Length 6.12 mm; width 3.85 mm. Color: Head, pronotum, elytra, legs, and venter brown. Head (Figs. 7, 8): Frons slightly convex; surface rugo-strigulate. Frontoclypeal suture obsolete. Clypeal shape subtrapezoidal, anterior margin straight, surface rugo-strigulate. Clypeal anterior declivital surface developed (Fig. 8), surface smooth. Labrum transverse, anterior margin indented; dorsal surface with sparse setae. Mandibles protruding beyond labral apex, dorsoventrally flat. Labial surface sparsely setose, setae long, labial palps with 4 palpomeres. Maxillary palps with 4 palpomeres. Eyes visible in dorsal view. Antennae with 9 antennomeres; antennomere 2 cylindrical, 3 slightly conical, 4-6 moniliform; antennal club with 3 antennomeres; basal antennomere of club cup-shaped, capable of receiving penultimate and ultimate antennomeres. Pronotum (Figs. 6, 8): Shape convex, pronotum 0.57 times as long as wide; surface mostly moderately punctate, slightly rugo-punctate on apical half in middle; punctures moderate in size. Anterior margin with weak bead and membrane well developed; lateral margins nearly straight, beaded, denticulate with long setae; posterior margin beaded. Anterior angles acute; posterior angles right-angled. Scutellum. Shape sub-triangular. Elytron (Fig. 6): Globose, apex rounded; surface with 10, punctate striae, lateral striae only evident in middle; interval surface punctate, punctures moderately dense. Lateral margin glabrous. Epipleuron only developed on elytral basal half, surface smooth, wider at base, tapered toward middle. Venter. pro-, meso-, metasternum, and abdominal sternites surface smooth, sparsely setose, setae long, slender; prosternal shield with posteromedial process poorly developed, not erected. Six abdominal sternites exposed, basal sternite only visible on lateral view. Legs (Figs. 7, 8): Protibia with 3 teeth and 3 denticles on outer margin; basal tooth small, middle and apical teeth well developed, curved; tibial dorsal surface with 2 setose, longitudinal carinae, outer carinae only reaches medial tooth; outer margin setose, setae moderately long; protibial spur shorter than apical tibial tooth, curved, apex acute. Meso- and metatibial apex expanded. Mesoand metatibiae with 1 transversal carina; with two apical, acuminate (mesotibia) and spatulate (metatibia) spurs. Pro-, meso-, and metatarsomeres 1 longer than 2; tarsomeres 2-4 subequal in length; tarsomere 5 longer than 4. Pro-, meso-, and metatarsal claws 0. 5.times as long as tarsomeres 5, simple, curved.






Etymology. I take great pleasure in naming this species after my cousin and goddaughter Caroline Maricourt.

Male: unknown.

Type material. Holotype female at IADIZA labeled: "ARGENTINA: Formosa / RP 39 23 km S Ing. Juarez / 24[degrees]05'27" S 61[degrees]56'49" W / 13-17-XII-08. F. Ocampo / G. San Blas., F. Campon / MV&UV light trap"; " Metachaetodus / carolineae / F. C. Ocampo 2010 / HOLOTYPE" (red label).

Distribution (Fig. 9). ARGENTINA. Formosa: Ingeniero Juarez (23 km S).

Key to species of Metachaetodus

1. Body distinctively unicolor, brown or light brown ... 2

1'. Body bicolored, head, pronotum and elytral disc dark brown to black, elytral margins light brown (Fig. 5) ... M. discus De Borre

2. Body light brown, lateral margins of pronotum lacking denticles ... M. brunneicollis De Borre

2'--Body dark brown, lateral margins of pronotum with denticles (Figs. 6-8) ... M. carolineae sp. nov.


I am grateful to all the curators and collection managers listed in the material and methods section for loans of specimens and/or making material accessible for this study. This project was supported by NSF (The National Science Foundation, USA) through the following grants: Advances in Biological Informatics # 0743783, and AToL # EF-0531768, and by CONICET (Consejo Nacional de Investigaciones Cientificas y Tecnicas, Argentina) through the grant PIP #112-200801-01869. Finally, I thank CONICET and the Instituto de Ciencias Basicas (ICB), Universidad Nacional de Cuyo, for their permanent support to my research.


(1.) ALLSOPP, P. G. 1984. Checklist of the Hybosoridae (Coleoptera: Scarabaeidae). Coleopterists Bulletin 38: 105-177.

(2.) BORRE, A. P. de. 1886. Liste des lamellicornes laparosstictiques recueillis par feu Camille van Volxem pendant son voyage au Bresil et a la Plate en 1872 suivie de la description de dix huit speces nouvelles et un genre nouveau. Annales de la Societe Entomologique de Belgique 30: 103-120.

(3.) MARTINEZ, A. 1994. Notas sobre Hybosorinae (Coleoptera: Scarabaeidae), II. Elytron 8: 223-239

(4.) OCAMPO, F. C. & A. BALLERIO. 2006. Phylogenetic analysis of the scarab family Hybosoridae and monographic revision of the of the New World subfamily Anaidinae (Coleoptera: Scarabaeoidea). 4. Catalog of the subfamilies Anaidinae, Ceratocanthinae, Hybosorinae, Liparochrinae, and Pachyplectrinae (Hybosoridae). Bulletin of the University of Nebraska State Museum 19: 178-209.

(5.) OCAMPO, F. C. & D. C. HAWKS. 2006. Phylogenetic analysis of the scarab family Hybosoridae and monographic revision of the of the New World subfamily Anaidinae (Coleoptera: Scarabaeoidea). 2. Molecular phylogenetics and systematic placement of the family Hybosoridae (Coleoptera: Scarabaeoidea). Bulletin of the University of Nebraska State Museum 19: 7-12.

(6.) SCHMIDT, J. O. 1913. Coleoptera Lamellicornia, Fam. Scarabaeidae, Subfam. Aegialiinae, Chironinae, Dynamopinae, Hybosorinae, Idiostominae, Ochodaeinae, Orphninae. Genera Insectorum 150: 1-87.

OCAMPO, Federico C.

Laboratorio de Entomologia, Instituto Argentino de Investigaciones de las Zonas Aridas, CCT-CONICET-Mendoza, C.C. 507, 5500 Mendoza, Argentina; e-mail:
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Author:Ocampo, Federico C.
Publication:Revista de la Sociedad Entomologica Argentina
Date:Jul 1, 2010
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