Atta octospinosa echinatior

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Atta octospinosa echinatior
Scientific classification (junior synonym of Acromyrmex octospinosus)
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Acromyrmex
Species: Atta octospinosa echinatior
Forel, 1899

Acromyrmex echinatior casent0909421 p 1 high.jpg

Acromyrmex echinatior casent0909421 d 1 high.jpg

Specimen Labels

This taxon is not in use as it is currently considered to be a junior synonym of Acromyrmex octospinosus.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • echinatior. Atta (Acromyrmex) octospinosa var. echinatior Forel, 1899c: 34 (w.q.) MEXICO (Chihuahua), GUATEMALA, COSTA RICA, PANAMA.
    • Type-material: lectotype worker (by designation of Schultz, Bekkevold & Boomsma, 1998: 461), paralectotype workers (number not stated).
    • Type-locality: lectotype Guatemala: Vera Paz, Senahu, El Reposo, Zapota, 800 ft (Champion); paralectotypes: with same data and from other original syntype localities.
    • [Note: other original syntype localities: Mexico: Chihuahua, Montezuma (Cockerell), Costa Rica: Volcán de Irazu (Rogers), Panama: Volcán de Chiriqui, Bugaba (Champion) (invalid restriction of type-locality by Wheeler, W.M. 1937c: 72 (in text); no lectotype designated).]
    • Type-depository: MHNG.
    • Wheeler, W.M. 1937c: 72 (m.).
    • Combination in Acromyrmex: Emery, 1924d: 350.
    • Junior synonym of octospinosus: Emery, 1905c: 44.
    • Subspecies of octospinosus: Forel, 1912e: 181; Emery, 1924d: 350; Santschi, 1925a: 391 (in key); Wheeler, W.M. 1937c: 71; Wheeler, W.M. 1938: 252; Santschi, 1939e: 319 (in key); Santschi, 1939f: 166 (in key); Weber, 1941b: 125; Kempf, 1972a: 14; Bolton, 1995b: 55.
    • Status as species: Schultz, Bekkevold & Boomsma, 1998: 460; Branstetter & Sáenz, 2012: 257.
    • Junior synonym of octospinosus: Mera‐Rodríguez et al. 2024: 12.
    • Distribution: Colombia, Costa Rica, Ecuador, Guatemala, Mexico, Panama.

Taxonomic Notes

Schultz et al. (1998) provided the following notes on this taxon before it was considered a junior synonym of Acromyrmex octospinosus:

Acromyrmex octospinosus var. echinatior was described by Forel (1900) and elevated to subspecies status by Wheeler (1937). These authors, as well as Santschi (1925), recognized A. octospinosus echinatior principally by the sculpture of the head and gaster of the major worker: “the tubercles on the posterior corners of the head, the pedicel, and the gaster are more developed and subspiniform, and some of those on the sides of the head are distinctly curved forward” (Wheeler, 1937).

WORKERS: In the fifty nests excavated in Panama, the largest major workers of A. echinatior are the same size as those of Acromyrmex octospinosus. However, a previous study by Bot and Boomsma (1997) found that pronotum width in A. echinatior (species 1 in that study) was significantly smaller than pronotum width in A. octospinosus (species 2 in that study). Qualitatively, major workers of the two species differ in the following ways: In A. echinatior the lateral pronotal spines are nearly vertical and parallel in frontal view, the vertical angle noticeably different from the angle of the anterior mesonotal spines, which diverge. In A. octospinosus, the anterior spines are not vertical and both pairs of spines diverge at approximately the same angle. Major workers of A. echinatior are hairier than those of A. octospinosus; e. g., at least some setae are present on the face of the propodeal dorsum in addition to those associated with the propodeal spines and with the anterior tubercles, whereas in A. octospinosus such setae are absent. In general, tubercles on the gaster of A. echinatior workers are sharp and dentiform to subspiniform, whereas those in A. octospinosus are low and blunted. Likewise, tubercles on the head of A. echinatior are sharp and spiniform, whereas those of A. octospinosus are shorter and blunter. We caution, however, that there is overlap between the two species in the form of the spines of the gaster and head and that these commonly cited characters are therefore not entirely reliable. Worker color is quite variable, ranging from yellow in callows to yellowish-ferrugineous to ferrugineous, with, as noted by Wheeler (1937) some workers acquiring a “bluish bloom.”

When workers from the entire range of both species are taken into account, the most constant distinguishing characters are the form of the spines on the head and gaster and to a lesser extent the differing angles of the lateral pronotal vs. anterior mesonotal spines. Major workers of A. echinatior from Costa Rica, Nicaragua, Guatemala, and Mexico, including the lectotype, frequently lack setae on the propodeal dorsum and are often much larger than those from the Panamanian nests.

FEMALES: In the Panamanian nests, A. echinatior females are smaller than Acromyrmex octospinosus females, and differ from them in the presence of a pigment spot entirely surrounding the ocelli (absent in the Panamanian A. octospinosus), the presence of setae on the propodeal dorsum (absent in A. octospinosus), and the presence of a broadly convex median anteroventral postpetiolar extension (variable in A. octospinosus). The occipital tubercle is thin and sharp and the tubercles on the first gastric tergite are sharp and dentiform; in A. octospinosus the occipital tubercle is thick and blunt, and the gastric tubercles are blunt and rounded. Color variation in females corresponds to that in workers. Over the whole of the species’ Central American range, A. echinatior females are more variable in size than in the Panamanian sample, tending to be larger, and variable in the presence/absence of the ocellar pigment spot.

MALES: In the Panamanian nests, A. echinatior males are the same size as A. octospinosus males, but differ from them by the presence of a pigmented frontal triangle that is entirely delineated by rugae (unpigmented and ill-defined in A. octospinosus), the presence of setae on the propodeal dorsum (absent in A. octospinosus), and the presence of a broadly convex median anteroventral postpetiolar extension (variable in A. octospinosus). Color is yellow-ferrugineous. A. echinatior males over the rest of the species’ range are variable in the characters of the frontal triangle.

Assigning the Panamanian specimens to A. echinatior is not without problems. The largest Panamanian workers are smaller than the lectotype and smaller than other worker specimens from Costa Rica, Nicaragua, Guatemala, and Mexico. Differences also exist in the characters of the propodeal setae (all castes), the ocellar pigment spot in females, and the form of the frontal triangle in males. Although the conservative position taken here is that these differences fall within the normal range of variation expected from a species distributed over a wide area, we would not be at all surprised to find that both Acromyrmex octospinosus sensu lato and Acromyrmex echinatior are composed of a number of cryptic species. If this is established by future research, then the Panamanian host of Acromyrmex insinuator may require species status separate from A. echinatior.

References

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