Strumigenys serrula

Bolton (1983) - S. serrula nests in pieces of rotting wood embedded in the leaf litter and topsoil layers, and preys on the isotomid collembolan Folsomia candida Willem. Its predatory behaviour has been investigated in some detail by Dejean (1980a; 1980b).

Identification
Bolton (2000) - A member of the Strumigenys lujae-group. Apicoscrobal hair present, flagellate; pronotal humeral hair flagellate. Pronotal dorsum strongly reticulate-punctate, the surface sometimes also with very feeble striae also present. Mesonotum with 3-4 pairs of standing hairs, the posteriormost pair situated at or very close to the metanotal groove and curved posteriorly. Ground-pilosity on head and promesonotum spatulate, conspicuous and quite dense, elevated rather than appressed. Standing hairs on head consisting of a transverse row of 4 close to the occipital margin and sometimes also a more anteriorly situated pair; these hairs only slightly longer and stouter than the ground-pilosity. Bullae of femoral glands small and ovate on all legs, somewhat variable in size and position but usually about two-thirds to three-quarters the way along the femoral dorsum.

Bolton (1983) - This widespread persistently small species is related to Strumigenys concolor and Strumigenys lujae. Together the three are characterized by their lack of an enlarged basal series of mandibular denticles, presence of cephalic flagellate hairs and dense reticulate-punctate pronotal sculpture. The differences separating serrula and Strumigenys concolor are tabulated under the latter name. S. serrula is separated from lujae by its size and pilosity. The largest specimens of serrula only overlap the very smallest individuals of lujae (serrula HW 0.34-0.44, SL 0.26-0.33; lujae HW 0.42-0.62, SL 0.32-0.58). Ground-pilosity everywhere on the head and promesonotum is relatively short, inconspicuous and closely applied to the surface in lujae. This gives the ant a rather smooth appearance and emphasises the long specialized hairs which stand out very conspicuously. In serrula the ground-pilosity is quite long and very distinctive, being markedly elevated from the surface so that the long specialized hairs which project from the ground pilosity are by no means as distinctive in appearance. On the mesonotum long hairs are restricted to a single anteriorly placed pair in lujae (or very exceptionally a second pair may be present, sited very close to the first) whereas in serrula three pairs are generally present distributed along the length of the mesonotum and with the posteriormost pair at or very close to the metanotal groove. Finally the reticulate-punctate pronotal sculpture is usually more strongly developed and more sharply defined in serrula than in lujae and serrula frequently has superimposed fine longitudinal striae or rugulae on the punctate surface.

Distribution based on Regional Taxon Lists
Afrotropical Region: Angola, Burundi, Cameroun, Chad, Congo, Democratic Republic of Congo, Gabon, Ghana, Ivory Coast, Kenya, Sudan, São Tomé & Principe, Uganda, United Republic of Tanzania.

Biology
This is a widespread species that has been collected across a range of wet forest habitats. It nests in dead wood and is typically found in litter samples.

Nomenclature

 *  serrula. Strumigenys lujae var. serrula Santschi, 1910c: 390 (w.) CONGO. Combination in S. (Trichoscapa): Santschi, 1913b: 258 (in key); in S. (Cephaloxys): Wheeler, W.M. 1922a: 920; Emery, 1924d: 324; in Serrastruma: Brown, 1952e: 81; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 127. Raised to species: Santschi, 1911c: 361. Senior synonym of uelensis: Brown, 1952e: 81. See also: Bolton, 1983: 349; Bolton, 2000: 317.
 * uelensis. Strumigenys (Cephaloxys) uelensis Santschi, 1923e: 289, fig. 4 (w.) DEMOCRATIC REPUBLIC OF CONGO. Junior synonym of serrula: Brown, 1952e: 81.

Worker
TL 1.9-2.3, HL 0.44-0.54, HW 0.34-0.44, CI 75-88, ML 0.15-0.18, MI 32-37, SL 0.26-0.33, SI 65-82, PW 0.24-0.30, AL 0.48-0.56 (50 measured).

Mandibular denticles evenly sized to the base or minutely and very gradually increasing in size basally, the basalmost denticle usually enlarged but never with a series of 4-8 obviously enlarged basal denticles. Upper scrobe margins regular or with a shallow impression at the site of the flagellate hair. Ground-pilosity of head narrowly spatulate, quite dense and very conspicuous, curved anteriorly and elevated, not closely applied to the surface. Dorsum of head with an occipital transverse row of 4 standing longer hairs which are usually cylindrical and tapered apically, only very rarely with their apices slightly swollen. Commonly a more anteriorly situated pair of similar hairs is present, just in front of the highest point of the vertex. All of these standing hairs are only slightly longer and stouter than the curved hairs of the ground-pilosity. Entire dorsum of head sharply and strongly reticulate-punctate. Dorsal alitrunk with the convex promesonotum sloping posteriorly to the impressed metanotal groove. Propodeal dorsum convex and sloping down to the teeth, the latter usually acutely triangular but variable in size; infradental lamellae present down the sides of the propodeal declivity. Sides of pronotum and the pleurae punctate, the punctures on the mesopleuron often more superficial and more widely spaced than elsewhere; infrequently the punctures superficial everywhere on the sides. Dorsal alitrunk strongly reticulate-punctate everywhere, the punctures sharply defined and the pronotum often with feeble longitudinal rugulae or striae which when present are very obviously secondary to the punctate component. Pronotum with elongate flagellate hairs at the humeri. Mesonotum with 3 (rarely 4) pairs of standing hairs; these are relatively slender, at most only feebly expanded apically. The posteriormost of these hairs is situated at or very close to the metanotal groove and is very variable in size. In some samples it is almost as long as the preceding mesonotal hairs but frequently is only as long as the ground-pilosity; whatever its length it is always directed posteriorly. Ground-pilosity on promesonotum quite long and conspicuous, dense and elevated, not closely applied to the surface. In profile the spongiform appendages of the pedicel segments moderately developed, the ventral appendage of the petiole may be reduced to a narrow ridge but is usually spongiform. Lateral and ventral spongiform lobes of postpetiole present. In dorsal view the surfaces of both the petiole and postpetiole reticulate to reticulate-punctate, sometimes the sculpture superficial and faint. Posterior spongiform strips of both segments narrow as is the basal strip on the first gastral tergite. Basigastral costulae present but frequently short and widely spaced, the gaster otherwise unsculptured. Petiole and postpetiole always with more than one pair of standing hairs, the gaster with numerous hairs. These vary from almost cylindrical to very weakly expanded apically, not strongly clavate. Colour dull yellow to yellowish brown.

Type Material
Bolton (1983) - Holotype worker, CONGO: Brazzaville (A. Weiss) [examined].