N. ensifer was originally a part of the genus Aphaenogaster until a recent phylogenetic study concluded that Novomessor was genetically distinct and should be separated.

While nothing is known about its reproduction, nuptial flight may take place during spring or summer, where queens establish their nests under stones and other objects.

[2] Among the genus Aphaenogaster, Italian entomologist Carlo Emery placed N. ensifer in the subgenus Deromyrma in 1915, although this is now a synonym.

The exact type locality for N. manni is unknown, but entomologist Paul Kannowski speculates that the ant is restricted to arid scrub forests around the Pacific Slope in Mexico.

English myrmecologist Barry Bolton argues that basing the genus on such feature cannot justify the separation of Novomessor and Aphaenogaster.

[7] In 2015, a phylogenetic study concluded that Novomessor was genetically distinct from Aphaenogaster, and the genus was revived from synonymy to include N. ensifer, N. albisetosus and N. cockerelli as members of it.

[10] The posterior to the eyes are convex, where it converges towards the occiput (the back of the head) and forms a collar seen in several Aphaenogaster species.

It is more sparse on the coxae, genae (an area on both sides of the head below the eyes), gaster and gula (the reduced sternite of the first segment of the thorax).

The node is evenly round and oval shaped, the postpetiole is narrow at the front and the dorsum is feebly convex.

[5] N. ensifer is endemic to Mexico and can be found in tropical dry forests at altitudes of between 115 and 1,700 ft (35 and 518 m) above sea level.

[9] The ant is found throughout several Mexican states within the east, including Guerrero and Michoacán from the south, and Colima and Jalisco from the north.

Scrub-thorn forests are also abundant, consisting of trees and shrubs that are 15 and 25 ft (4.6 and 7.6 m) tall, but other areas may contain low herbs and grasses.

Other identified plants and trees include Indian mallows (Abutilon), spurred anodas (Anoda cristata), Cathestecum erectum, dayflowers (Commelina), cigar plants (Cuphea), hairy crabgrass (Digitaria sanguinalis), crane grass (Ixophorus unisetus), Mimosa, Mexican panicgrass (Panicum hirticaule), Senna uniflora and Setaria liebmannii.

A single path connects the entrance to the main nest site, followed by a passage that descends straight into the dirt several inches deep.

[9] When a worker discovers a dead insect, it will start to pull and carry it back to the nest immediately, and other nestmates will join once they detect it.

However, it is possible that nuptial flight takes place in spring or summer, and like N. albisetosus and N.cockerelli, alates most likely start to occur by June.

[9] After nuptial flight, queens search for a suitable colony by building a chamber under objects such as stones and exposed roots of woody plants.

This theory stated by entomologist Paul Kannowski is supported by the fact that these ants depend on stones buried in the soil for nest construction.