Acanthoponera minor

Longino (Ants of Costa Rica) - A. minor appears to be a ubiquitous inhabitant of lowland wet forest throughout Costa Rica. The species is not restricted to wet forest, because I once observed foragers to be abundant in a small pasture with scattered guava trees. The pasture was adjacent to a forest patch, so I do not know if the species requires forest as a source area. Almost the only way I ever see this species is as workers and queens scattered sparsely on low vegetation at night. At La Selva, they have been collected in dawn canopy fogging events and in Malaise traps. From these observations I conclude: (1) both workers and queens forage, (2) foraging is solitary, and (3) foraging is almost entirely nocturnal. Foragers are furtive when illuminated at night, and thus it is very difficult to follow foragers back to a nest. I observed one nest entrance at Corcovado: a small clay turret extending 1-2cm up the side of an erect plant stem.

Identification
Brown (1958) described the now synonomized  Acanthoponera crassa and his notes about how these differ from minor provides details about morphological variation within this species: Considered as belonging to Acanthoponera crassa is a short series of workers [USNM, MCZ] from Hamburg Farm, Santa Clara Prov., Costa Rica, February 26, 1925 (F. Nevermann leg.). The MCZ specimen measures HL 1.19, HW excluding eyes 1.03 mm. (CI 87). The color is much lighter than in the type series, being bright ferruginous yellow, and the occipital angles are somewhat more abruptly rounded; transverse part of occipital border broader than in type, concave in middle. Eyes a little larger, propodeal teeth shorter and feebly bent in side view, and the posterapical petiolar teeth flattened and only slightly deflected dorsad.

In color and head shape, the Costa Rican samples are somewhat intermediate, tending toward minor, but in the characters of total size, metanotal groove and petiolar thickness and form, they are clearly related to crassa. The differences from minor could possibly represent geographical variation; but the known distribution of minor and crassa does not support this very well.

Distribution based on Regional Taxon Lists
Neotropical Region: Colombia, Costa Rica, Ecuador, Guatemala, Honduras, Mexico, Trinidad and Tobago, Venezuela.

Nomenclature

 * . Ectatomma (Acanthoponera) mucronatum var. minor Forel, 1899c: 9 (w.) MEXICO (Tabasco).
 * [Acanthoponera minor Emery, 1896g: 33. Nomen nudum (attributed to Forel).]
 * Combination in Acanthoponera: Emery, 1911d: 36.
 * Subspecies of mucronata: Emery, 1911d: 36; Wheeler, W.M. 1923e: 189.
 * Status as species: Brown, 1958g: 194; Kempf & Brown, 1968: 89; Kempf, 1972a: 9; Fernández, 1993: 251; Bolton, 1995b: 54; Arias-Penna & Fernández, 2008: 112; Branstetter & Sáenz, 2012: 256; Feitosa & Prada-Achiardi, 2019: 675.
 * Senior synonym of crassa: Kempf & Brown, 1968: 90; Kempf, 1972a: 9; Bolton, 1995b: 54.
 * Senior synonym of schwarzi: Brown, 1958g: 194; Kempf, 1972a: 9; Bolton, 1995b: 54.
 * Senior synonym of spininodis: Brown, 1958g: 194; Kempf, 1972a: 9; Bolton, 1995b: 54.
 * crassa. Acanthoponera crassa Brown, 1958g: 255, fig. 10 (w.) ECUADOR, COSTA RICA.
 * Junior synonym of minor: Kempf & Brown, 1968: 90; Kempf, 1972a: 9; Bolton, 1995b: 53.
 * schwarzi. Acanthoponera goeldii subsp. schwarzi Wheeler, W.M. 1923e: 188, fig. 5 (w.) GUATEMALA.
 * Junior synonym of minor: Brown, 1958g: 194; Kempf, 1972a: 9; Bolton, 1995b: 54.
 * spininodis. Acanthoponera (Acanthoponera) spininodis Weber, 1939a: 97, fig. 2 (w.) TRINIDAD.
 * Junior synonym of minor: Brown, 1958g: 194; Kempf, 1972a: 9; Bolton, 1995b: 54.

Description
Brown (1958), for the synonymized Acanthoponera crassa - Holotype worker: TL 6.2, HL 1.24, HW excluding eyes 1.07 (Cr 86), greatest diameter of eye 0.30, scape L 0.85, WL 1.82 mm.

Similar to Acanthoponera minor, but a little larger. Head narrowing from a point in front of eyes toward occiput, narrowest, and sides sloping inward, behind eyes near the much-rounded occipital corners; occipital margin short, median section straight, or even feebly convex. Median pronotal eminence low, but better developed than in other species of the genus. Metanotal groove distinct, broad and rather deep. Propodeal spines (L ca. 0.35 mm.) straight and obliquely elevated as seen from the side; diverging, with tips feebly curved mesad as seen from above. Petiolar node thicker than in minor, its posterapical tooth deflected more or less dorsad. Gaster very much like that of minor in general form, but slightly larger.

Sculpture in general a little coarser on head, alitrunk and node than in minor, the interspaces larger and shining. Pronotal rugules forming a V around the median eminence. Gaster smooth, shining, with abundant fine, separated punctulae, giving rise to dense, reclinate golden-brown pubescence. Longer fine erect hairs abundant.

Body color orange-brown, legs more yellowish.

Type Material
Brown (1958), Acanthoponera crassa - Holotype one of a series of 4 workers taken 6 miles west of Santo Domingo de los Colorados, Pichincha, Ecuador, February 23, 1955 (E. S. Ross and E. I. Schlinger leg.). The remaining three workers are paratypes CAS,. HL 1.22-1.25 mm., CI 87-89.

References based on Global Ant Biodiversity Informatics

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 * Longino, J.T. 2010. Personal Communication. Longino Collection Database
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 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
 * Weber N. A. 1939. New ants of rare genera and a new genus of ponerine ants. Ann. Entomol. Soc. Am. 32: 91-104.
 * Wheeler W. M. 1923. Ants of the genera Myopias and Acanthoponera. Psyche (Cambridge) 30: 175-192.