Acropyga silvestrii

Lapolla (2004) - Even though the species is found in savanna type habitat in many places across its range, A. silvestrii apparently does not overlap with Acropyga arnoldi, which is found exclusively in southern Africa.

Identification
From Lapolla (2004):

Diagnosis - Worker: Antennae 11-10 segmented; head distinctly longer than broad; head width not greater than 0.5 mm; in lateral view pronotum with short shelf; mesosomal dorsum flat, with appressed hairs. Queen: unknown. Male: unknown. Compare with Acropyga arnoldi and Acropyga paleartica.

This species can be easily separated from Acropyga arnoldi by its size (A. silvestrii TL: 1.6-2.1; HW: 0.383-0.454 versus A. arnoldi TL: 2.1-2.4; HW: 0.517-0.619). Differentiation from Acropyga paleartica can be slightly more difficult, though the torulae of A. silvestrii are very closely set together (almost touching medially) and their mandibles do not have offset basal teeth.

The relationship of this species to A. arnoldi is unclear since males remain unknown. A. silvestrii is observed with up to 7 teeth, but has not been observed with at least a 4-segmented maxillary palp as in A. arnoldi and A. paleartica.

Key to Old World Acropyga Workers

Distribution based on Regional Taxon Lists
Afrotropical Region: Eritrea, Ghana, Kenya, Rwanda, Togo, Uganda, United Republic of Tanzania. Palaearctic Region: Ethiopia.

From LaPolla (2004): The distribution of A. silvestrii stretches from western Africa as far south and east as northern Tanzania. This is the only Acropyga known from the rainforests of Africa, which is interesting because in other areas where rainforests are found the diversity of Acropyga is substantially higher. The low species diversity found in Africa may be an artifact of collecting since there are few collections from Africa (particularly West Africa) available for study, or may indicate something of biological interest.

Habitat
The species is found in a variety of habitats from tropical savannas to rainforests; it has also been collected from cacao plantations. It has been recorded from elevations up to 1600 m.

Castes
Known only from the worker caste.

Nomenclature

 *  silvestrii. Acropyga silvestrii Emery, 1915g: 21, fig. 11 (w.) ETHIOPIA. Combination in Acropyga (Malacomyrma): Emery, 1922d: 109. See also: LaPolla, 2004a: 78.

Worker
From LaPolla (2004) - Head: yellow to slightly brownish yellow; covered in dense layer of appressed hairs; head distinctly longer than broad; posterior margin entire; 11-10 segmented, incrassate antennae; apical segment about as long as proceeding 3 segments; scape fails to reach posterior margin by about length of pedicel; clypeus medially slightly convex, with several erect hairs; mandible with 4-7 uneven teeth; inner mandibular margin nearly parallel with anterior clypeal margin. Mesosoma: yellow; pronotum in lateral with a short shelf, then rising steeply toward mesonotum; mesonotum flat, covered in layer of appressed to suberect hairs; metanotal area often distinct; propodeum at about same height as mesonotum, rounded toward a steep declivity. Gaster: petiole thick and erect, rounded at apex; gaster yellow; covered in a thick layer of appressed hairs, with suberect to erect hairs scattered throughout.

Measurements Worker (n= 10): TL: 1.16-2.15; HW: 0.383-0.454; HL: 0.429-0.506; SL: 0.297- 0.349; ML: 0.425-0.567; GL: 0.64-1.16; CI: 84.0-95.18; SI: 72.12-82.2.

Queen
Queens are not known for this species.

Male
Males are not known for this species.

Type Material
Acropyga silvestrii Emery, 1915: 21. 5 syntype workers, ERITREA: Ghinda [1 worker examined]. The designated lectotype is a worker labeled JSL TYPE # 125 and is deposited at MHNG. Emery, 1922: 109, combination in subgenus Malacomyrma.