Strumigenys crassicornis Mayr, 1887

Silva, Thiago Sanches Ranzani Da, Chaul, Júlio Cezar Mário & Feitosa, Rodrigo Machado, 2022, Lectotype designation and redescription of four commonly collected Neotropical species of Strumigenys (Hymenoptera: Formicidae), European Journal of Taxonomy 798 (1), pp. 103-126 : 106-111

Strumigenys crassicornis Mayr, 1887

Figs 1–2

Strumigenys crassicornis Mayr, 1887: 577 .

Neostruma crassicornis – Brown 1948: 111.

Pyramica crassicornis – Bolton 1999: 1672.

Strumigenys crassicornis – Baroni Urbani & De Andrade 2007: 117.

Diagnosis

Strumigenys crassicornis is one of the most easily diagnosable Neotropical Strumigenys and can be distinguished from other species by the combination of lobate scape near subbasal bend ( Fig. 2A ), spatulate cephalic ground-setae ( Fig. 2A ), absence of apicoscrobal setae ( Fig. 2A ), and swollen postpetiole ( Fig. 2B ).

Type material

Lectotype (designated herein) (label information) ( Fig. 1 ) BRAZIL • “ St. Cath. Hetschko ” [printed]; “Collect. G. Mayr [printed]; “ crassicornis ” [handwritten] “ G. Mayr, Type” [printed]; “ Pyramica crassicornis ” [handwritten] “det. B. Bolton 1999” [printed]; “Syntype” [printed]; “ANTWEB CASENT0915943” [printed]; “ Strumigenys crassicornis Mayr, 1887 ” LECTOTYPE [printed]; “ NHMW-HYM4945 ” [printed]; NHMW.

Paralectotypes (label information) BRAZIL • 1 worker; “ St. Catharina Coll. G. Mayr ” [printed]; “Syntype” [printed]; “ Strumigenys crassicornis Mayr, 1887 PARALECTOTYPE” [printed]; “ NHMW-HYM4946 ” [printed]; NHMW • 1 worker; same label information as for preceding; “ NHMW-HYM4947 ” [printed]; NHMW • 1 worker; same label information as for preceding; “ NHMW-HYM4948 ” [printed]; NHMW .

Additional material examined

BRAZIL – Amazonas • 2 workers; Terra Firme ; 02°34′ S, 60°06′ W; 7 Dec. 1990; M.O. de Oliveira leg.; ZF-02, km 10, Capoeira small caps or capital?; CELC, UFV-LABECOL009312 . – Bahia • 2 workers; Itacaré ; 14°17′38.0″ S, 38°59′08.6″ W; 23 Oct. 2015; J. Chaul leg.; CELC, UFV-LABECOL-001967 . – Espírito Santo • 1 worker; Santa Teresa , “Rebio Augusto Ruschi” [ Augusto Ruschi Biological Reserve ], Preguiça [Preguiça Trail]; 19°54′42.1″ S, 40°32′24.0″ W; 800–870 m a.s.l.; Jan. 2013; S. Simon leg.; CELC, UFV-LABECOL-010752 . – Mato Grosso • 1 worker; Canarana ; 13°04′ S, 52°23′ W; Jun. 2013; M. Bicalho and V. Ribeiro leg.; Winkler; CELC, UFV-LABECOL-000064 . – Minas Gerais • 1 worker; Viçosa ; 13 Jan. 1998; A.M. Soares leg.; CELC, UFV-LABECOL-001842 • 1 worker; Viçosa ; Feb. 1994; Sperber, Louzada and Lopes leg.; floresta secundária; CELC, UFV-LABECOL-001824 • 1 worker; Viçosa ; 14 Nov. 2008 – 9 Feb. 2009; E.A. Silva and M. Rodrigues leg.; mata do paraíso ; CELC, UFV-LABECOL-001838 • 2 workers, 1 queen; same collection data as for preceding; CELC, UFV-LABECOL-010753 • 1 worker, 1 queen; same collection data as for preceding; CELC-UFV- LABECOL-011011 • 1 worker; same collection data as for preceding; CELC-UFV-LABECOL-010760 • 1 worker; Viçosa ; 20°48′08″ S, 42°51′31″ W, 13–18 Mar. 2011; L. Paolucci leg.; mata do paraíso ; Berlese; CELC, UFV-LABECOL-001794 • 1 worker; same collection data as for preceding; CELC-UFV-LABECOL-001764 • 1 worker; same collection data as for preceding; CELC-UFV- LABECOL-001793 • 1 worker; same collection data as for preceding; CELC-UFV-LABECOL-001770 • 1 worker; same collection data as for preceding; CELC-UFV-LABECOL-001767 • 1 worker; same collection data as for preceding; CELC-UFV-LABECOL-001782 • 1 worker; same collection data as for preceding; CELC-UFV-LABECOL-001768 • 1 worker; same collection data as for preceding; CELC-UFV-LABECOL-001762 • 1 worker; same collection data as for preceding; CELC-UFV- LABECOL-001796 • 1 worker; same collection data as for preceding; CELC-UFV-LABECOL-001774 • 1 worker; same collection data as for preceding; CELC-UFV-LABECOL-001776 • 1 worker; Viçosa; 2009–2010; A.S. Pereira leg.; mata do paraíso ; CELC, UFV-LABECOL-001833 • 1 worker, 1 queen; Viçosa ; 1 Apr. 2013; J. Chaul leg.; horto; hand sampled; CELC, UFV-LABECOL-001843 • 1 worker; Viçosa ; 20°45′26.67″ S, 42°51′39.07″ W; J. Chaul leg.; mata da biologia ; Winkler; CELC, UFV- LABECOL-001837 • 2 workers; Viçosa , 20°48′21.6″ S, 42°51′10.8″ W; 780 m a.s.l.; 1 May 2013; J. Chaul and R.S. Jesus leg.; mata do paraíso ; hypogaeic Winkler; CELC, UFV-LABECOL-1822 • 1 queen; same collection data as for preceding • 1 worker; Viçosa ; 20°48′ S, 42°51′ W; 12 Feb. 2015; J. Chaul and A.P. Alves leg.; mata do paraíso ; Winkler; CELC, UFV-LABECOL-001841 • 1 queen; Viçosa ; 20°48′19″ S, 42°51′13.1″ W; 685 m a.s.l.; 12 Jul. 2016; A.P. Raimundo, L. Ferreira, J. Chaul and L. Paolucci leg.; mata do paraíso ; hypogaeic Winkler; CELC, UFV-LABECOL-010759 • 1 worker; same collection data as for preceding; CELC, UFV-LABECOL-010756 • 1 worker; same collection data as for preceding; CELC, UFV-LABECOL-010757 • 1 worker; same collection data as for preceding; CELC, UFV-LABECOL-010758 • 1 worker; same collection data as for preceding; CELC, UFV- LABECOL-010761 • 1 worker; same collection data as for preceding; CELC, UFV-LABECOL-010762 • 1 worker; Araponga ; Apr. 2011; D. Muscardi leg.; CELC, UFV-LABECOL-001849 • 1 worker,; Parque Estadual da Serra do Brigadeiro ; 20°39′16″ S, 42°24′58″ W; 1400 m a.s.l.; Jan. 2007; R. Solar leg.; CELC, UFV-LABECOL-009313 • 2 workers, 1 queen; same collection data as for preceding; CELC, UFV-LABECOL-00145 • 4 workers; same collection data as for preceding; CELC, UFV- LABECOL-0018200 • 2 workers; Araponga-Fervedouro , “ Serra do Brigadeiro ”; 20°44′21.9″ S, 42°27′20.6″ W; 16 Oct. 2016; N. Safar and T. Fernandes leg.; Serra do Brigadeiro ; CELC, UFV- LABECOL-009314 • 2 workers; same collection data as for preceding; CELC, UFV-LABECOL-009311 • 1 worker; Alto Caparaó , Vale Verde; 6 Nov. 2016; A. Orsetti and S.Alóquio leg.; Winkler; CELC, UFV- LABECOL-009309 • 1 worker; same collection data as for preceding; CELC, UFV-LABECOL-009310 • 1 queen; Providência ; 21°40′43.7″ S, 42°38′19.0″ W; Dec. 2012; J. Chaul leg.; Fazenda Araribá ; Winkler; CELC, UFV-LABECOL-001835 • 1 worker, 1 queen; Parque Estadual do Itacolomi ; 20°25′34.8″ S, 43°30′53.7″ W; 25–31 Oct. 2016; G. Soares, J. Falcon, L.F. Climaco and T. Pontes leg.; grotão ; CELC, UFV-LABECOL-010729 • 2 workers; Serra do Cipó “ Próx. Cachoeira da Capivara” [near Cachoeira da Capivara]; 19°15′10.7″ S, 43°33′06.4″ W; 1351 m a.s.l.; 13 May 2016; J. Chaul and S. Epifânio leg.; CELC, UFV-LABECOL-001909 • 1 worker; same collection data as for preceding; CELC, UFV- LABECOL-001906 • 1 worker; Ipaba , “ Faz. Macedônia” [Macedônia Farm] ; Nov. 2005; T. Marques leg.; CELC, UFV-LABECOL-001819 . – Pará • 2 workers; Primavera ; 00°58’45″ S, 47°06’43″ W; 5–6 Nov. 2018; L.P. Prado and K.L.S. Sampaio leg.; Winkler; CELC, UFV-LABECOL-010463 • 1 worker; same collection data as for preceding; CELC, UFV-LABECOL-011010 . – Rondônia • 1 worker; Jaci Novo ; 6 Jul. 2013; km 3; INPA, ANTWEB1032004 . – Santa Catarina • 2 workers; Indaial , Parque Nacional da Serra do Itajaí, Faxinal do Bepe; Feb. 2015; M.D. Vitorino leg.; regeneração; DZUP • 3 workers; same collection data as for preceding; Apr. 2015; DZUP • 1 worker; same collection data as for preceding; Jun. 2015; DZUP • 2 workers; same collection data as for preceding; Aug. 2015; DZUP • 2 workers; same collection data as for preceding; Feb. 2016; DZUP • 3 workers; same collection data as for preceding; Aug. 2016; DZUP • 1 worker; same collection data as for preceding; Aug. 2015; floresta; DZUP • 1 worker; same collection data as for preceding; Aug. 2015; poleiro; DZUP • 1 worker; same collection data as for preceding; Jun. 2016; DZUP • 2 workers; same collection data as for preceding; Feb. 2016; galharia; DZUP • 1 worker; same collection data as for preceding; Aug. 2016; DZUP • 3 workers; same collection data as for preceding; Aug. 2016; plantio; DZUP • 2 workers; Painel, Base Avançada do IBAMA ; 18 May 2013; R.M. Feitosa leg.; solo; DZUP • 1 worker; Três Barras , Floresta Nacional de Três Barras; 26°13′48.444″ S, 50°17′45.21″ W; 723.513 m a.s.l.; 25 Apr. 2015; D.C. Ortiz and J. Niemyer leg.; DZUP • 1 worker; Três Barras , Floresta Nacional de Três Barras; 26°07′35.56″ S, 50°18′51.17″ W; 15 Dec. 2014; D.C. Ortis et al. leg.; DZUP • 1 worker; Seara ; 1999; R. Silva leg.; MZSP, ANTWEB1032393 • 1 worker; Araranguá , Restinga Morro dos Conventos ; 7–23 Jan. 2008; D.C. Cardoso and M.P. Cristiano leg.; CELC, UFV-LABECOL-001893 . – São Paulo • 1 worker; Salesópolis , Estação Ecológica de Boracéia; 23°39′19.0″ S, 45°53′17.0″ W; 3–11 Nov. 2017; R.P.S. Almeida and J.A. Silva leg.; Winkler; CELC, UFV-LABECOL-010754 .

Lectotype measurements

ABD4L 0.396; DPW 0.124; EL 0.052; HL 0.585; HT 0.288; HW 0.412; ML 0.230; PH 0.132; PL 0.277; PPL 0.149; PW 0.279; SL 0.201; WL 0.589; TL 1.954; CI 70.4; DPI 44.7; LPI 47.6; MI 39.3; OI 12.6; SI 48.8.

Non-type measurements

ABD4L 0.330 –0.470; DPW 0.105 –0.150; EL 0.040 –0.060; HL 0.480 –0.620; HT 0.250 –0.330; HW 0.340 –0.450; ML 0.155 –0.240; PH 0.130 –0.190; PL 0.220 –0.340; PPL 0.110 –0.200; PW 0.230 – 0.325; SL 0.210 –0.310; WL 0.465 –0.630; TL 1.765 –2.500; CI 70.1–78.8; DPI 39.7–50.0; LPI 48.3– 61.4; MI 32.3–38.7; OI 9.8–14.6; SI 53.8–70.6 (n = 14).

Description

SCULPTURE. Head entirely reticulate-punctate, including antennal scrobe. Mesosoma mostly reticulatepunctate, katepisternum partly smooth ( Fig. 2B ). Fourth abdominal tergite entirely smooth, except for basigastral costulae. Basigastral costulae short; in dorsal view, its length about a third of postpetiole length.

SETAE. Cephalic and mesosomal ground-setae spatulate ( Fig. 2A ). Metasomal setae elongate-spatulate to remiform. Apicoscrobal setae absent ( Fig. 2A ). Pair of erect setae on cephalic dorsum close to occipital margin present. Anterior margin of scape with one or more spatulate setae curved towards antennal insertion. Humeral setae absent and mesonotal setae present (but see Comments below).

HEAD. Masticatory margin of mandible with three to five denticles between apicodorsal tooth and submedian tooth, with two to four denticles proximal of submedian tooth ( Fig. 2A ). Apex of mandible with unknown number of intercalary denticles (but see Fig. 2A and Comments section for variation). Anterior clypeal margin, in dorsal view, slightly angular and projecting anteriorly. Eye, in lateral view, with four to five ommatidia in longest row. Eye on anterior half of head. In dorsal view, scape narrows basally; anterior margin expanded and almost lobate near subbasal bend. Third flagellomere smaller than fourth flagellomere; length of former only a third of length of latter.

MESOSOMA. Humerus with small angular projection. Dorsum of mesonotum, in lateral view, slightly higher than dorsum of pronotum. Metanotal groove weakly impressed. Propodeal spine relatively long and triangular, linked to propodeal lobe by narrow lamella that extends throughout propodeal declivity. Femoral bulla ovate and located distally on dorsal margin of sclerite.

METASOMA. Petiolar node, in dorsal view, slightly wider than long; in lateral view, anterior margin slightly longer than dorsal margin. Postpetiole, in lateral view, swollen and globular.Anterior margin of postpetiole, in dorsal view, medially concave. Ventral spongiform process of petiole absent. Ventral spongiform lobe of postpetiole minute to absent ( Fig. 2B ). Lateral spongiform lobe of postpetiole reduced to a narrow lamella ( Fig. 2B ). Ventral basigastral spongiform pad (= specialized setae on fourth abdominal sternite) small.

Comments

Bolton (2000) considered S. crassicornis as a member of the crassicornis complex (i.e., a cluster of species in the gundlachi species group), along with Strumigenys aethegenys ( Bolton, 2000) , S. auctidens ( Bolton, 2000), S. brevicornis Mann, 1922, S. crementa ( Bolton, 2000), S. metopia (Brown, 1959), S. myllorhapha (Brown, 1959), S. pasisops ( Bolton, 2000), S. stenotes ( Bolton, 2000), and S. zeteki (Brown, 1959). Members of the crassicornis complex are defined by the following traits ( Bolton 2000): (i) inner margin of mandible with a submedian tooth or denticle near midlength; (ii) inner margin of mandible with smaller teeth between apicodorsal tooth and submedian tooth; (iii) three to five intercalary teeth; (iv) labral lobes long and slender; and (v) setae on apices of labral lobes short (i.e., with the same size or shorter than the labral lobes).

According to Bolton (2000), different series of this species show slight variation in setae and sculpture, although maintaining the diagnostic traits for the species. He mentioned that some specimens possibly have short filiform humeral setae, although this condition was not observed in the type specimen and a few other individuals observed in this study. Additionally, a pair of mesonotal erect simple setae, which was not mentioned by Mayr (1887) nor Bolton (2000) in their descriptions, was also observed in the lectotype and a few other specimens. Humeral and mesonotal setae are apparently lost during the lifetime of the ants, since many specimens, otherwise well preserved, did not have those setae and most of the ones which did have them appear to be young adults by the appearance of their cuticle. Also, some specimens had an extremely reduced lateral spongiform lobe in the postpetiole, appearing vestigial, agreeing with the description made by Bolton (2000).

In Bolton’s (2000) description, the author mentions that S. crassicornis have three to four minute intercalary teeth. Since we did not had access to the physical lectotype specimen, we could not confirm this condition. However, while studying other non-type specimens, we observed that the intercalary dentition consists of up to six to seven teeth. Interestingly, these intercalary teeth count does not agree with the diagnosis proposed by Bolton (2000) for the crassicornis complex.

In specimens collected in Orleans and Tunas do Paraná (cf. list of examined materials), the katepisternum appears entirely reticulate-punctate, without smooth patches whatsoever. Different specimens collected in the same square meter (from Winkler leaf-litter samples) possess both reticulate-punctate katepisternum and various degrees of smoothness. One specimen from Viçosa (Minas Gerais State) and one specimen from the Reserva Biólogica Augusto Ruschi (Espírito Santo State) also have an entirely reticulate-punctate katepisternum. In Viçosa, all the other specimens examined matched the lectotype in having a smooth katepisternum. The morphological variability in this particular character, summed with the higher intercalary teeth count found in some non-type specimens observed, reinforces the need for a reevaluation of the boundaries of this species.

In the Amazonian region, non-type specimens identified as S. crassicornis tend to depart further from the lectotype, differing in one or more traits, and do not entirely match the species’ diagnosis. One specimen from Primavera (Pará State) has shallow reticulation on fourth abdominal tergite. A couple of specimens from Amazonas state (vicinities of Manaus; cf. additional material examined ZF-02) have an almost entirely reticulate-punctate katepisternum and shallow reticulation on fourth abdominal tergite. A specimen from Canarana (Mato Grosso State) has shallow reticulation on fourth abdominal tergite and humeral and mesonotal setae which are not simple, but slightly flattened and subflagellate. A couple of specimens, also from Primavera, have shallow reticulation on fourth abdominal tergite, basigastral costulae absent, spongiform process on postpetiole absent, and smaller and less abundant metasomal erect setae. Finally, one specimen from “Jaci Novo’’ (Rondônia State) is much larger than all examined specimens, has both humeral and mesonotal setae flattened and subflagellate, and a comparatively larger postpetiole, with shallow reticulation on fourth abdominal tergite.

Figures

Fig. 1. Lectotype of Strumigenys crassicornis Mayr, 1887 (CC-BY, CASENT0915943, Anna Pal, from www.antweb.org). A. Head, mandibles and antennae, in dorsal view.B. Full body, in lateral view. C. Full body, in dorsal view.

Fig. 2. Generalized schematics of Strumigenys crassicornis Mayr, 1887, showing useful identification features. A. Head in dorsal view. B. Mesosoma, petiole, and postpetiole in lateral view.