Strumigenys lujae

Strumigenys lujae nests in rotten wood and forages there and in the leaf litter layer. In a letter William L. Brown has informed me that the prey are collembolans. Speaking of his observations in Banco Forest, Ivory Coast, made in 1963, he says ‘The S. lujae nest was in the split end of a log and consisted of many, perhaps a thousand or more, workers and copious brood. I found the nest by following a single-file trail of workers along the top of the log, spaced out at intervals of 4-10 cm, almost everyone of which carried in its jaws a dead (or at least motionless) entomobryid collembolan with furcula extended. The Collembola were about the same size as the ants carrying them, or slightly larger. In the space of about 10 minutes I counted 40 springtails being carried along the log on what appears to have been a trunk foraging trail. No other kinds of insect prey were seen being carried or lying within the dissected nest.’ (Bolton 1983)

Identification
Bolton (2000) - A member of the Strumigenys lujae-group. An extremely common, very widely distributed species that shows considerable size variation. Mandible without an enlarged basal series of denticles but masticatory margin usually with an enlarged denticle at about one quarter to one third of the length from the apex, and another about half way between this and the apical tooth; generally these are not conspicuous unless the mandibles are open. Apicoscrobal hair present. Cephalic dorsum with a pair of simple standing hairs just in front of highest point of vertex, and with a transverse row of 4 close to the occipital margin. Pronotum densely reticulate-punctate and with a flagellate humeral hair. Mesonotum with 1, or very rarely 2 pairs of stout standing hairs situated anteriorly on the sclerite. Postpetiole with 2 or more pairs of standing hairs.

Bolton (1983) - This very successful, common, widely distributed species shows a size range in workers which is notably greater than in any other Serrastruma (a genus that is now a synonym of Strumigenys).

The closest relatives of lujae are Strumigenys serrula and Strumigenys concolor, the three together sharing the characters of dense reticulate-punctate sculpture on the pronotal dorsum and lack of an enlarged series of basal denticles on the mandible. Beside these features other easily observed characters useful in separating lujae and its immediate allies from the other species of the genus are as follows. In Strumigenys dotaja the mesonotum is equipped with a single pair of extremely long flagellate hairs scrobe margins lack projecting hairs. In Strumigenys simoni the spongiform appendages of the pedicel segments are more massively developed. In Strumigenys ludovici, beside the enlarged mandibular denticles, the head has only a single pair of standing hairs, situated posteriorly. The minute Strumigenys miccata has short mandibles, lacks projecting hairs on the upper scrobe margins and has straight clavate hairs at the pronotal humeri.

S. serrula and concolor are both persistently small species, only overlapping the lower end of the size range given for lujae. S. serrula is separated from lujae by having 3 or 4 pairs of mesonotal standing hairs and elevated ground-pilosity on the head and alitrunk. S. concolor has 2 or 4 clavate standing hairs on the head (as opposed to 6 relatively fine hairs in lujae), and has only a single pair of hairs on the postpetiole. Beside this most concolor specimens show a marked indentation or impression of the upper scrobe margin at the site of origin of the projecting flagellate hair.

Distribution based on Regional Taxon Lists
Afrotropical Region: Angola, Burundi, Cameroun, Democratic Republic of Congo, Equatorial Guinea, Gabon, Ghana, Guinea, Ivory Coast, Kenya, Mozambique, Nigeria, Rwanda, South Africa, Sudan, São Tomé & Principe, Uganda, United Republic of Tanzania, Zimbabwe.

Biology
Brown (1952) - S. lujae is clearly a sylvicolous species, and the most commonly collected form of Serrastruma in the equatorial forest belt and adjacent gallery-forests. Its presence on the islands in the Gulf of Guinea and in plant shipments at Honolulu indicates with what ease it can spread to new areas. The nests are made in rotten wood or in the soil or soil cover. I have examined series from nests containing up to 300 workers and four or five queens plus numerous winged forms of both sexes, males predominating. Males are often present as fully-pigmented free imagoes while the majority of the females are still in the pupal stage. Large nests are often infested with an apparent myrmecophile - a small ferruginous staphylinid beetle.

Nomenclature

 *  lujae. Strumigenys lujae Forel, 1902e: 294 (footnote), pl. 1, fig. 1 (w.) MOZAMBIQUE. Combination in S. (Trichoscapa): Santschi, 1913b: 258 (in key); in S. (Cephaloxys): Wheeler, W.M. 1922a: 920; Emery, 1924d: 324; in Serrastruma: Brown, 1952e: 78; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 123. Senior synonym of aequalis, gerardi, glanduscula, reticulata: Brown, 1952e: 78; of calypso: Bolton, 1983: 345. See also: Bolton, 2000: 315.
 * reticulata. Strumigenys reticulata Stitz, 1910: 141 (w.) CAMEROUN. Junior synonym of lujae: Brown, 1952e: 78.
 * glanduscula. Strumigenys (Cephaloxys) glanduscula Santschi, 1919h: 88 (w.) DEMOCRATIC REPUBLIC OF CONGO. Junior synonym of lujae: Brown, 1952e: 78.
 * calypso. Strumigenys (Cephaloxys) calypso Santschi, 1923e: 288, fig. 4 (w.) TANZANIA. Combination in Serrastruma: Brown, 1952e: 85. Junior synonym of lujae: Bolton, 1983: 345.
 * gerardi. Strumigenys (Cephaloxys) gerardi Santschi, 1923e: 287 (w.) DEMOCRATIC REPUBLIC OF CONGO. Junior synonym of lujae: Brown, 1952e: 78.
 * aequalis. Strumigenys (Cephaloxys) aequalis Menozzi, 1942: 177 (w.q.) EQUATORIAL GUINEA (Bioko I.). [Also given as new in Eidmann, 1944: 457.] Junior synonym of lujae: Brown, 1952e: 78.

Worker
Bolton (1983) - TL 2.2-3.3, HL 0.50-0.80, HW 0.42-0.62, CI 75-86, ML 0.18-0.32, MI 33-42, SL 0.32-0.58, SI 75-100, PW 0.30-0.66, AL 0.58-0.98 (55 measured).

Mandibular denticles regular, without a suddenly enlarged basal series but sometimes the denticular row very evenly and gradually becoming slightly larger towards the base; the basalmost denticle frequently larger than those preceding. Upper scrobe margins with a long simple or weakly flagellate hair projecting laterally just behind the level of the eyes. Dorsum of head reticulate-punctate everywhere, the sculpture fine and even. Ground-pilosity of dorsal head consisting of narrowly spatulate anteriorly curved short hairs which are decumbent or closely applied to the surface. Standing pilosity of head consisting of a posterior transverse row of 4 hairs situated close to the occipital margin and a more anteriorly situated pair just in front of the highest point of the vertex. The standing hairs are usually simple and more or less cylindrical, often pointed apically but sometimes very weakly swollen at their apices. Alitrunk in profile with the promesonotum convex and sloping posteriorly to the impressed metanotal groove. Behind the metanotal groove the propodeum is shallowly convex and sloping to the teeth posteriorly. Propodeal teeth very variable in shape and size, varying from obtuse angles to strong triangular teeth. Infradental lamellae present on the propodeal declivity but often narrow. Sides of alitrunk often reticulate-punctate everywhere but with some variation in intensity. The sides of the pronotum may be only faintly sculptured and, in some cases, the mesopleuron may be partially or entirely smooth. A central smooth patch may also occur on the metapleuron. Dorsal alitrunk reticulate-punctate everywhere, the punctation on the pro no tum usually fine and very dense. Sometimes the intensity of the sculpture reduced so that the punctures are less well defined than usual. Pronotum with humeral flagellate hairs present. Mesonotum with a single pair (or exceptionally with 2 pairs) of stout standing hairs situated anteriorly on the sclerite. Ground-pilosity of dorsal alitrunk of scattered finely spatulate hairs which are decumbent to appressed and inconspicuous. With the pedicel segments in profile the spongiform appendages moderately developed. In dorsal view the petiole and postpetiole both bounded posteriorly by a narrow lamellate spongiform strip, both usually punctate or finely reticulate dorsally though on the postpetiole the sculpture may be almost effaced. Base of first gastral tergite with a narrow lamellar strip and with basigastral costulae present. Petiole with one or more pairs of standing stout hairs, the postpetiole with 2 or more pairs; first gastral tergite with numerous similar hairs. Colour yellow to medium brown.

Type Material
Bolton (1983) - Syntype workers, MOZAMBIQUE: Zambesi, Morrumballe (E. Luja) [examined].