Diagnosis among workers of introduced and commonly intercepted species. Antenna 12-segmented. Antennal scape length less than 1.5x head length. Eyes medium to large (greater than 5 facets); eye length not distinctly greater than length of erect hairs on frontal carinae. Antennal sockets and posterior clypeal margin separated by a distance less than the minimum width of antennal scape. Mandible lacking distinct basal angle. Dorsum of mesosoma with metanotal groove, but never with a deep and broad concavity; erect hairs present. Propodeum and petiolar node both lacking a pair of short teeth. Propodeum lacking posteriorly projecting protrusion; with dorsal surface distinctly shorter than posterior face. Waist 1-segmented (may be hidden by gaster). Petiolar node appearing flattened. Gaster armed with ventral slit; with five plates on its dorsal surface. Distinct constriction not visible between abdominal segments 3+4. Hairs Dorsum of head with one pair of long and thin erect hairs posterior to eye. Pronotum with 1 pair of erect hairs. Mesonotum with erect hairs. Propodeum with 2 pairs of erect hairs. Color uniformly dull brown with paler antennae, trochanters and tarsi; hind tarsus distinctly lighter in color than hind femur.
Technomyrmex difficilis can be distinguished from Brachymyrmex species, with which it bears superficial resemblance, by the 12-segmented (versus 9-segmented) antenna, and by the presence of a ventral slit (versus acidopore) on the gaster tip. It can be differentiated from Technomyrmex species by the absence (versus presence) or erect hairs on the mesosoma, and by the gaster which has 4 plates on the dorsal surface and 6 on the ventral surface (versus 5 plates on both surfaces). It is most easily differentiated from Tapinoma sessile by the bicolored with dark head and light body, gaster and appendages (versus uniform brown color). Technomyrmex difficilis is distinguished from its fellow introduced congeners by the following combination of characters: (1) Dorsum of head with one pair of long and thin erect hairs posterior to eye; (2) 1 pair of erect hairs on pronotum, 2 pair of propodeum, erect hairs present on mesonotum,; (3) hind tarsus distinctly lighter in color than hind femur; and (4) eye length is not distinctly greater than length of erect hairs on frontal carinae.
Brachymyrmex, Tapinoma sessile, Technomyrmex albipes, Technomyrmex pallipes, Technomyrmex vitiensis