Nomamyrmex esenbeckii ( Westwood, 1842 )

Shattuck, Steve & Cover, Stefan, 2016, Taxonomy of some little-understood North American ants (Hymenoptera: Formicidae), Zootaxa 4175 (1), pp. 10-22 : 19

Nomamyrmex esenbeckii ( Westwood, 1842)

Labidus esenbeckii Westwood, 1842: 75 . Holotype male, Vendinha [29°47′S 51°33′E], Brazil, 10 September 1828 (W. Burchell) (Oxford University Museum of Natural History) [https://www.antweb.org/specimen/ CASENT0901959].

Eciton crassicorne mordax Santschi, 1929: 415 . Holotype worker, Cernavaca [18°55′N 99°13′W], Mexico (Naturhistorisches Museum Basel) [https://www.antweb.org/specimen/CASENT0911413]. New synonym.

Eciton esenbecki wilsoni Santschi, 1920: 366 . Holotype male, Las Borragas, near Brownsville [25°54′N 97°30′W], Texas, June [year uncertain] (C. Schaeffer) (Brooklyn Museum, not seen). New synonym.

As noted by Watkins (1977), Nomamymrex esenbeckii has accumulated a large number of names to describe its various forms. The number of these names considered as valid has gradually decreased as additional material has revealed intermediate morphologies, diverse combinations of character states and distinct geographic patterns. As a result we are currently down to just a single species with two recognized subspecies, N. mordax and N. wilsoni ( Watkins, 1977; Wild, 2007). However, even this relatively simple system has proven problematic. In a detailed but unpublished analysis, Roy and Gordon Snelling (http://www.armyants.org/armyants/genusaccounts/ nomamyrmex / noma.html, accessed 19 June 2014) provide the following notes:

“It is true that the morphological features on which the several subspecies of N. esenbeckii are based are generally representative of their respective populations. Equally true, however, is that many specimens within these populations do not possess the required characteristics of that named population. Samples from areas of sympatry are, as may be expected, intermediate between the respective phenotypes. In the worker caste, there is a north/south trend that is continuous. In northern specimens, the posterior margin of the mesonotum, in dorsal view, is definitely concave, and the longitudinal rugules of the propodeal dorsum are short and weak. Proceeding into Central America and through South America, the margin of the mesonotum becomes straight or even convex; the propodeal rugulae strengthen and run the entire length of the dorsal face. Similar trends are evident in the male structures employed by Watkins (1977) in segregating N. esenbeckii into four subspecies. In fact, differences in genitalic structures may be greater within any given population than those that separate purported subspecies. Under the circumstances, there would appear to be little justification for these subspecies and we propose to reduce all to synonymy.”

Wild (2007) accepted these recommendations when he synonymized N. crassicorne and we now apply this careful analysis by the Snellings to the remaining subspecies.

Nomamymrex esenbeckii is exceptionally widespread, occurring from southern Texas , United States, south through Central America to northern Argentina and Paraguay .