Plagiolepis exigua
Diagnosis of worker among Antkey species. Worker caste monomorphic. Head ovoid (HL > HW). Antenna 11-segmented. Antennal club indistinct. Antennal scape short, not exceeding the posterior head margin by a distance greater than half the eye length. Eyes medium to large (greater than 5 facets); do not break outline of head. Posterior head margin weakly concave. Dorsum of mesosoma lacking metanotal impression; lacking erect hairs. Propodeum and petiolar node both lacking a pair of short teeth. Propodeum lacking posteriorly projecting protrusion. Metapleuron with a distinct gland orifice. Waist 1-segmented (may be hidden by gaster). Petiole upright and not appearing flattened. Gaster armed with acidopore. Distinct constriction not visible between abdominal segments 3+4. Color light brownish yellow.
The only other genera with 11-segmented antenna among the introduced or commonly intercepted species in the United States are Anoplolepis and Lepisiota. Plagiolepis can be distinguished from Anoplolepis species by the significantly smaller size (< 2 mm) and relatively short appendages. It can be distinguished from Lepisiota by the lack of teeth arming the propodeum and petiolar node. The only other genera of formicine with species that lack a metanotal impression is Camponotus, from which Plagiolepis is distinguished by its much smaller size, monomorphic worker caste, and shorter antennal scapes.
Plagiolepis exigua can be separated from P. alluaudi and P. pygmaea by the shorter antennal scapes that do not exceed the posterior head margin by a distance greater than half the eye length. It can be further separated from P. alluaudi by its ovoid head that is longer than wide ovoid head that is longer than wide (versus circular head that is as long as wide), and the weakly concave (versus strongly convex) posterior head margin. It can be further distinguished from P. pygmaea by the light yellowish (versus dark brown) color.
Plagiolepis alluaudi, Plagiolepis pygmaea.