Holcoponera striatula

A common, widespread species that exhibits wide variation in some characters. It commonly nests in twigs within leaf litter (Fernandes et al., 2018).

Identification
A member of the striatula subgroup (in the striatula species group). This widespread, common, and fairly variable ant has been the object of a lengthy synonymic list. Most of the names were based upon differences in size, gauge of costulation, and the shape of the subpetiolar process and the mesopisternal lobe. These size differences are all normal for the species. One can recognize coarsely costulate and finely costulate specimens, as well as intermediate forms. The finely costulate ants can be found in several places: S. Brazil, Argentina, Guiana, Costa Rica, Jamaica and Hispaniola. Occasional series can be found that have transverse costulae on part or all of the propodeal declivity; this condition is not frequent on the finely costulate forms. Several series from Bolivia have a long anterior slope of the node, which approaches the condition in pleurodon. The use of the subpetiolar process in the separation of species is of limited value as a variation from subquadrate to anteriorly projecting lobe can be found in series from the same population or even nest. Brown (1957:489) already discussed the futility of using the mesepisternal lobe. (Lattke 2004)

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Barbados, Bolivia, Brazil, Colombia, Costa Rica, Dominican Republic, Ecuador, French Guiana , Greater Antilles, Guadeloupe, Guatemala, Guyana, Lesser Antilles, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Suriname, Trinidad and Tobago, Uruguay, Venezuela.

Biology
Rosumek (2017) examined trophic and temporal niches of ants in a secondary Atlantic forest (Florianópolis, south Brazil; ), between December 2015 and January 2016. For this species: Gnamptogenys striatula (possibly a species complex) is a rare example of a Neotropical ant extensively studied in the laboratory, covering many aspects of its biology (e.g. Giraud et al., 2000; Kaptein et al., 2005). However, the only information available about its trophic niche in the wild comes from Lattke (1990), who reports remnants of several insect orders inside nests, and posteriorly called it “a generalist epigeic forager of humid forests” (Lattke, 1995). A recent account recorded it rarely on experimental vertebrate carcasses left to rot in a forest, predating the larvae and pupae of necrophagous insects (Paula et al., 2016).

At baits in this study, G. striatula  was observed using termites frequently, but crushed insects, feces and sucrose were important as well. Hence, the species will scavenge and consume sugar when given the opportunity, although they were not attracted to melezitose (an oligossacharide analog used as a proxy for honeydew). The relatively high use of feces, a less preferred resource overall, is a noteworthy feature that differentiated G. striatula from most other species of this study. It showed a moderate but significant preference for nocturnal foraging.

Lattke (1995) - A mite was found on the anterolateral petiolar side of one specimen from Beni, Bolivia.

De la Mora et al. (2016) found this species nesting in logs found in coffee farms and forests in the Soconusco region of Chiapas, Mexico.

Koch et al. (2018) sampled this species in Caryocar barsiliense trees, in southeastern Brazil cerrado, as part of a study examining species interactions in ant-plants.

Worker
Several gamergates reproduce in most colonies, while one or several dealate queens reproduce in others. Cuticular Hydrocarbons differ qualitatively and quantitatively between egg-laying and infertile workers, thus providing reliable information about current fertility (Lommelen et al. 2006).

Nomenclature

 *  striatula. Gnamptogenys striatula Mayr, 1884: 32 (w.) FRENCH GUIANA. Mayr, 1887: 542 (q.m.); Gallardo, 1918b: 26 (q.m.); Wheeler, G.C. & Wheeler, J. 1952a: 123 (l.). Combination in Ectatomma (Holcoponera): Mayr, 1887: 541; in Holcoponera: Emery, 1911d: 40; in Gnamptogenys: Brown, 1958g: 229. Senior synonym of obscurum: Santschi, 1929h: 442; of antillana: Brown, 1956b: 490; of angustiloba (and its junior synonym vollenweideri), angustipleura, brasiliensis, calcarata, paulina, pernambucana, and material of the unavailable name hybrida referred here: Brown, 1958g: 229; of arcuata, curtulum (and its junior synonym stolli), recta, rustica, simplicoides, wasmanni (and its junior synonym isthmica), wheeleri (and its junior synonym mayri): Lattke, 1995: 186.
 * curtulum. Ectatomma (Holcoponera) curtulum Emery, 1896g: 47, pl. 1, fig. 8 (w.) COSTA RICA. Forel, 1899c: 7 (q.). Combination in Holcoponera: Emery, 1911d: 40; in Gnamptogenys: Brown, 1958g: 228. Senior synonym of stolli: Brown, 1958g: 228. Junior synonym of striatula: Lattke, 1995: 186.
 * obscurum. Ectatomma (Holcoponera) obscurum Emery, 1896g: 48 (w.) BRAZIL. Combination in Holcoponera: Emery, 1911d: 41. Subspecies of striatula: Forel, 1908c: 341. Junior synonym of striatula: Santschi, 1929h: 442.
 * stolli. Ectatomma (Holcoponera) curtulum var. stolli Forel, 1899c: 7 (w.m.) GUATEMALA. Combination in Holcoponera: Emery, 1911d: 40. Subspecies of curtulum: Santschi, 1929h: 470. Junior synonym of curtulum: Brown, 1958g: 228.
 * brasiliensis. Holcoponera brasiliensis Emery, 1902a: 181 (w.q.m.) BRAZIL. Wheeler, G.C. & Wheeler, J. 1952a: 124 (l.). Junior synonym of striatula: Brown, 1958g: 229.
 * angustiloba. Ectatomma (Holcoponera) striatulum var. angustiloba Forel, 1908c: 341 (w.) BRAZIL. Forel, 1911e: 254 (q.); Gallardo, 1918b: 23 (m.). Combination in Holcoponera: Emery, 1911d: 41. Subspecies of brasiliensis and senior synonym of vollenweideri: Santschi, 1929d: 275; Santschi, 1929h: 453. Junior synonym of striatula: Brown, 1958g: 229.
 * angustipleura. Ectatomma (Holcoponera) striatulum var. angustipleura Forel, 1908c: 342 (w.) BRAZIL. Combination in Holcoponera: Emery, 1911d: 41. Raised to species: Santschi, 1929h: 456. Junior synonym of striatula: Brown, 1958g: 229.
 * paulina. Ectatomma (Holcomyrmex) curtula var. paulina Forel, 1908c: 342 (Holcomyrmex here is an error for Holcoponera) (w.) BRAZIL. Combination in Holcoponera: Emery, 1911d: 40. Subspecies of brasiliensis: Santschi, 1929h: 456. Junior synonym of striatula: Brown, 1958g: 229.
 * simplicoides. Ectatomma (Holcoponera) striatulum var. simplicoides Forel, 1908c: 341 (w.) BRAZIL. Santschi, 1929h: 455 (m.). Combination in Holcoponera: Emery, 1911d: 41; in Gnamptogenys: Brown, 1958g: 229. Subspecies of brasiliensis: Santschi, 1929h: 454. Raised to species: Brown, 1958g: 229. Junior synonym of striatula: Lattke, 1995: 186.
 * vollenweideri. Holcoponera curtula var. vollenweideri Forel, 1912c: 33 (w.) ARGENTINA. Junior synonym of angustiloba: Santschi, 1929d: 275; Santschi, 1929h: 453.
 * antillana. Holcoponera striatula var. antillana Santschi, 1929h: 444, figs. 16, 21 (w.m.) MARTINIQUE I. Junior synonym of striatula: Brown, 1956b: 490.
 * arcuata. Holcoponera regularis var. arcuata Santschi, 1929h: 457 (w.) BRAZIL. Combination in Gnamptogenys: Brown, 1958g: 227. Junior synonym of, and hence first available replacement name for, Holcoponera regularis Santschi, 1929d: 275 [Junior secondary homonym of Gnamptogenys regularis Mayr, 1870b: 965.] and raised to species: Brown, 1958g: 227. Junior synonym of striatula: Lattke, 1995: 186.
 * calcarata. Holcoponera brasiliensis var. calcarata Santschi, 1929h: 452, fig. 28 (w.) BRAZIL. Junior synonym of striatula: Brown, 1958g: 229.
 * recta. Holcoponera emeryi var. recta Santschi, 1929h: 465 (w.) BOLIVIA. Junior synonym of pleurodon: Brown, 1958g: 229; of striatula: Lattke, 1995: 186.
 * regularis. Holcoponera regularis Santschi, 1929d: 275 (w.) BRAZIL. [Also described as new by Santschi, 1929h: 457.] [Junior secondary homonym of regularis Mayr, above.] Senior synonym of arcuata and hence the latter the first available replacement name for regularis Santschi: Brown, 1958g: 227.
 * rustica. Holcoponera rustica Santschi, 1929h: 446, figs. 11, 18 (w.) PARAGUAY. Combination in Gnamptogenys: Brown, 1958g: 229. Junior synonym of striatula: Lattke, 1995: 186.
 * wasmanni. Holcoponera wasmanni Santschi, 1929h: 466, fig. 42 (w.) BRAZIL. Combination in Gnamptogenys: Brown, 1958g: 230. Senior synonym of isthmica: Brown, 1958g: 230. Junior synonym of striatula: Lattke, 1995: 186.
 * wheeleri. Holcoponera rustica st. wheeleri Santschi, 1929h: 448, figs. 9, 19 (w.) COSTA RICA.
 * Wheeler, G.C. & Wheeler, J. 1952a: 124 (l.).
 * Combination in Gnamptogenys: Brown, 1958g: 230.
 * Status as species: Brown, 1958g: 230; Bolton, 1995b: 211.
 * Senior synonym of mayri: Brown, 1958g: 230.
 * Junior synonym of striatula: Lattke, 1995: 186.
 * isthmica. Holcoponera wasmanni var. isthmica Santschi, 1929h: 467 (w.) PANAMA. Junior synonym of wasmanni: Brown, 1958g: 230.
 * mayri. Holcoponera brasiliensis var. mayri Santschi, 1929h: 453 (w.) COSTA RICA.
 * Junior synonym of wheeleri: Brown, 1958g: 230.

Taxonomic Notes
Lattke (1995): Diagnosis - Pronotal costulae semicircular; dorsoposterior mesosomal costulae longitudinal and slightly diverging caudad; mesometanotum sometimes with semiciruclar costulae; triangular metacoxal teeth; body dark brown.

Specimens determined as G. curtula by Brown for the 1958 revision are G. striatula, and so are several specimens determined as H. wasmanni var. isthmica. Specimens labelled as type series of H. emeryi recta were studied in the USNM and found to be conspecific with striatula and not with G. pleurodon. I was able to examine two G. striatula syntypes in the BMNH. Bill Brown generously shared the notes he took during his study of the following Santschi types in 1963: H. regularis, H. regularis v. arcuata, H. rustica, and H. wheeleri. He concluded that they are all the same species. He also wrote that these specimens plus additional types and specimens he studied (H. striatula v. antillana, v. angustipleura, H. wasmanni, H. wasmanni v. isthmica, H. brasiliensis v. calcarata, v. mayri, H. curtula v. paulina (det. Santschi)) perhaps could be separated into two species using the subpetiolar process. But as already has been mentioned, this process has proven to be an unreliable character for species determination in this group.