Plagiolepis alluaudi
Diagnosis of worker among Antkey species. Worker caste monomorphic. Head circular (HL = HW). Antenna 11-segmented. Antennal club indistinct. Antennal scape exceeding the posterior head margin by a distance greater than half the eye length; less than 1.5x head length. Eyes medium to large (greater than 5 facets); do not break outline of head. Posterior head margin strongly convex. 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 uniformly 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 alluaudi can be separated from both P. exigua and P. pygmaea by its circular head that is as long as wide (versus ovoid head that is longer than wide) and by the strongly convex (versus weakly to moderately concave) posterior head margin. It can be further distinguished from P. exigua by the longer antennal scapes that exceed the posterior head margin by a distance greater than half the eye length, and from P. pygmaea by the light yellowish (versus dark brown) color.
Plagiolepis exigua, Plagiolepis pygmaea