Triacrus dilatus Nordmann, 1837

Chatzimanolis, Stylianos, 2015, New Records, Redescription, and Notes on Nomenclature forTriacrusNordmann (Coleoptera: Staphylinidae: Staphylininae: Staphylinini), The Coleopterists Bulletin 69 (3), pp. 514-520 : 516-519

Triacrus dilatus Nordmann, 1837 ( Figs. 1–7 )

Triacrus dilatus Nordmann, 1837: 18 . Staphylinus superbus Erichson, 1839: 398 .

Diagnosis. As for the genus.

Description. Body length 22–36 mm. Coloration of head and pronotum dark metallic blue; elytra dark metallic blue-purple with brown setation; mouthparts brown except mandibular prostheca, galea, and lacinia orange; antennae brown with dark yellow setation; ventral part of body, legs, and abdomen brown except segments VIII and IX orange. Head transverse but size variable; width: length ratio 1.31–1.16. Dorsal surface of head with polygon-shaped microsculpture and small punctures; punctures interspersed but denser near posterior, lateral, and ocular margins. Ventral surface of head with slightly larger, sparser punctures and polygon-shaped microsculpture. Antennomeres 1–3 longer than wide; antennomere 4 subquadrate; antennomeres 4–10 transverse, asymmetrical, becoming narrower distally. Pronotal width: length ratio = 1.22; with small punctures; punctation denser towards lateral sides and anterolateral corner, not as dense towards medial disc, impunctate near medial line; with uniform polygon-shaped microsculpture. Mesoscutellum with small, uniform, almost confluent punctation. Elytra with small, dense, almost confluent punctures and microsculpture. Abdominal tergites with small, dense, uniform punctation becoming denser towards posterior segments; abdominal sternites with similarly dense punctation but punctures slightly longitudinally elongate. Male secondary sexual structures with posterior border of sternite VII with broad, shallow emargination; sternite VII with porose structure (similar to that in Trigonopselaphus ; sternite VIII with broad U-shaped emargination medially; sternite IX with deep V-shaped emargination medially. Females with no obvious secondary sexual structures. Aedeagus as in Figs. 5–7 ; paramere in dorsal view shorter and much narrower than median lobe, slightly off center to right [this was observed in multiple specimens]; paramere converging to rounded apex; with peg setae ( Fig. 7 ); in lateral view, paramere curved upwards. Median lobe robust; in dorsal view, lateral sides almost parallel until converging abruptly near tip to rounded apex; in lateral view, median lobe slightly curved upwards; with single, small, dorsal tooth.

Holotype. Male, with labels: “5974” / “Type” [orange label] / “ superbus Er. dilatus Nordmann Brasil v. Lgsfd [Langsdorf]” [large teal label] / “Hist.-Coll. ( Coleoptera ) Nr. 5974 Stap[h]ylinus superbus Erichs. Brasilia v. Langsdorf Zool. Mus. Berlin” [green label] / “ Holotypus Triacrus dilatus Nordmann, 1837 labeled by MNHUB 2014 [red label]” / “ SYNTYPUS Triacrus superbus Erichson, 1839 labeled by MNHUB 2014” [red label]. In the collection of ZMHB. Nordmann (1837) specifically mentioned he had a single specimen, so this is the holotype for the species. The issues with Erichson’ s designation are discussed below in “Nomenclature”, however, another specimen is labeled as Syntypus of Triacrus superbus , but that specimen has no type status since the designation is based on the same type material and Nordmann had a single specimen.

Additional Specimens Examined. ARGENTINA: Misiones: Colonia Finlandesa , 16–17.x.[19]06, Matteson, GAC.7926 (1 male MZH); unknown locality, E. Kivirikko, GAC.7927 (1 female MHZ); unknown locality, Lunnasvaara, GAC.7928 (1 male MHZ) . BRAZIL: Espírito Santo: Trijuco Preto , 900m, iii.1940, Reitter, UTCI000004861 , UTCI000004866 (2 females NMW) ; unknown locality, Fruhstorfer , UTCI000004371 (1 male FMNH) ; unknown locality, Descourtilz , UTCI000004896 , UTCI000004897 (2 females BMNH) ; unknown locality, UTCI000004894 , UTCI000004895 (2 males BMNH) ; unknown locality (2 males ZMHB) ; Rio de Janeiro: unknown locality, Fry, UTCI000004875 , UTCI000004303 , UTCI000004294 (2 males, 1 female FMNH) ; unknown locality, in colony of Polybia vicina, 1901 , UTCI000004899 (1 female BMNH) ; same data, UTCI000004423 (1 male FMNH) ; Rio Grande do Sul: São Leopoldo, F. Schneider, UTCI000004855 (1 male NMW) ; São Leopoldo , UTCI000004869 (1 female NMW) ; unknown locality, UTCI000004891 , UTCI000004898 (1 male, 1 female BMNH) ; unknown locality, Pohl , UTCI000004879 (1 female FMNH) ; Paraná: unknown locality, E. D. Jones, UTCI000004878 (1 female FMNH) ; Santa Catarina: Blumenau, Hetschko , UTCI000004859 , UTCI000004867 (1 male, 1 female NMW) ; Corupá , xii.[19]63, UTCI000004873 (1 male FMNH) ; Hansa Humboldt Station , vii.1939, Reitter, UTCI000004865 (1 female NMW) ; Hansa Humboldt Station , xii.1939, UTCI000004870 (1 male UTCI) ; Nova Teutonia, x.1963 (1 male ZMUC); Pinhal, Antori Maller Carupo , ii.1968, UTCI000004854 (1 male NMW) ; Rio Capivari, Fruhstorfer , 1888, UTCI000004892 (1 male BMNH) ; Teresópolis, H. Rolle, UTCI000004877 (1 female FMNH) ; Teresópolis, Fruhstorfer (1 female ZMHB); Teresópolis, Jul. Michaelis (1 female ZMHB); unknown locality, UTCI000004872 (1 male MCZ) ; São Paulo: Fazenda Barreiro Rico, Anhembi , 19.xi.1965, W. D. Edmonds, meat trap, UTCI000004364 (1 male FMNH) ; São Paulo, UTCI000004853 (1 male NMW) ; unknown locality, Thering , UTCI000003995 (1 male FMNH) ; unknown locality, leg. Spite UTCI000004863 (1 female NMW) ; unknown state: unknown locality, Bang-Haas, UTCI000004133 (1 female FMNH) ; unknown locality, Deyrrolle , UTCI000004887 (1 male BMNH) ; unknown locality, Sahlberg , [1]850, UTCI000004876 (1 female FMNH) ; unknown locality, Klimsch donavit, UTCI000004862 (1 female NMW) ; unknown locality, UTCI000004889 , UTCI000004890 , UTCI000004893 (3 males BMNH) ; unknown locality, UTCI000003481 (1 male FMNH) ; unknown locality, UTCI000004858 (1 male NMW) ; unknown locality, UTCI000004860 , UTCI000004864 , UTCI000004868 (3 females NMW) ; unknown locality, Lund (1 male, 1 female ZMUC); unknown locality (4 females ZMUC). PA R A G U AY: I t a p ú a: H o h e n a u, i. 1 9 5 5, UTCI000004874 (1 male FMNH) . Unknown country: unknown locality, UTCI000004856 , UTCI000004857 (2 males NMW) ; unknown locality (2 females, 1 male [this is the “extra” syntype mentioned above in the Holotype section] ZMHB) .

Distribution. Found in the Atlantic forest of Argentina, Brazil, and Paraguay ( Fig. 8 ).

Ecology. Recently, Marlowe et al. (2015) studied the sexual dimorphism and allometry in these beetles. Triacrus dilatus is found in the debris piles of the paper wasp A. vicina . The wasps build large

nests, and according to Wasmann (1902) T. dilatus attack the fly larvae also present in the debris piles. Whether or not there are any direct interactions with the wasps is unknown. Wasmann also reported more than a hundred larvae and pupae attributed to Triacrus . However, I am skeptical if these larvae belong to Triacrus because the larvae illustrated were much smaller than Triacrus (assuming they were drawn on the same scale) and they were lacking urogomphi, a typical Xanthopygina feature ( Quezada et al. 1969; Irmler 1979; Chatzimanolis 2004b). Regardless of the illustration, Wasmann did refer to the larvae as large and with long “cerci” that could mean the urogomphi.

Some specimens have small mites attached to them, typically on the ventral side of the beetle.

Nomenclature. As stated above, T. dilatus was described by Nordmann during 1837. Erichson (1839) examined the materials and thought that the epithet dilatus was too close to dilatatus (referring here to Quedius (Velleius) dilatatus (F.)) and that Nordmann had confused the two species based on the similarity of their antennae (both asymmetrical). Erichson proposed the epithet superbus as a replacement name for dilatus based on the same holotype that Nordmann used. However, Nordmann was aware of the differences between the two species in two different genera. He described Triacrus on page 19 of his monograph and referred to Q. dilatatus , providing characters for this species on page 16. The name T. superbus is thus an unnecessary replacement name for T. dilatus , and T. superbus is a junior objective synonym of T. dilatus based on the same materials with no types of its own. It is worth pointing out here that T. superbus was the epithet used for this species until Herman (2001b) pointed out that T. dilatus had priority.

During the review process of this paper, one of the reviewers strongly questioned the above reasoning based on his/her interpretation of Erichson’ s text. The reviewer argued that Erichson produced a description of a new species and did not propose a replacement name. However, this view is erroneous for the following reasons: (1) Erichson did not provide any characters to separate the two species; (2) Erichson considered T. dilatus a synonym of his new name ( T. superbus ); and (3) he used the same specimen that Nordmann used as one of his syntypes.

Notes. The wasp A. vicina was first described as Polybia vicina de Saussure and later transferred to the genus Stelopolybia Ducke , which was later synonymized with Agelaia Lepeletier. Kistner (1982) misspelled the name Stelopolybia and used “Stenopolybia” in his treatise of symbionts of social insects.

Due to their large size, several of the Triacrus specimens were collected by famous 19 th century European explorers. There are a couple of specimens in London allowed me to photograph the specimen of T. dilatus for Fig. 1 .; they retain the copyright of the photograph. Partial financial support was provided by a Research and Creative Activity award from the College of Arts and Sciences at the University of Tennessee at Chattanooga.

labeled “Descourtilz” in the collection of BMNH, originally deposited in the Fry Collection. The labels probably refer to the French naturalist and illustrator Jean-Theodore Descourtilz (1796–1855) who worked in Espírito Santo during the mid-19 th century. In the ZMUC collection, there were some collected by Peter Wilhelm Lund (1801–1880), a Danish zoologist and paleontologist, and in several collections there are specimens from Hans Fruhstorfer (1866–1922), a German entomologist and explorer.

Note on the Lectotype Depository for Polyphematiana liliputana Bernhauer. Recently, Chatzimanolis (2013) described the genus Terataki and included several taxa previously in Gastrisus Sharp , Torobus Herman , and Trigonopselaphus . One of the species, Terataki liliputanum (Bernhauer) , was originally described in Polyphematiana Strand. In that paper, I designated a lectotype for the species but erroneously stated that the lectotype is in the collection of ZMHB; instead, it is deposited in FMNH.

Figures

Fig. 1. Habitus of Triacrus dilatus. Total length = 34 mm. Image copyright of the Natural History Museum (London).

Figs. 2–3. Triacrus dilatus. 2) Head and thorax, dorsal view; 3) Head, ventral view.

Fig. 4. Triacrus dilatus, abdominal sternites VII–IX.

Figs. 5–7. Triacrus dilatus, aedeagus. 5) Lateral view; 6) Dorsal view; 7) Paramere, ventral view.

Fig. 8. Distribution map of Triacrus dilatus.