Strumigenys horvathi

Workers were found by Wilson in northeastern New Guinea in leaf litter, apparently foraging, at several localities during daylight hours. Workers were also found under the bark of Zoraptera-stage logs, and were knocked from the underside of small Passalus-stage logs. No. 833 was a group of workers without queen or brood found in a small soil cavity under a wood chip buried in leaf litter, plus strays from the surrounding litter. No. 926 was a large colony with more than 150 workers taken under the bark of a Zoraptera-stage log. No. 1008 was a colony of 50-75 workers with one queen and abundant brood in all stages situated in a Passalus-stage rotten branch about 3-4 cm in diameter, buried in leaf litter. (Brown 1973)

Identification
Bolton (2000) - A member of the horvathi complex in the Strumigenys horvathi-group. S. horvathi differs from Strumigenys snellingi as the latter has a conspicuous pronotal humeral hair. In the material available the mandibles of horvathi appear slightly shorter (MI 35-40) than in snellingi (MI 42-46).

Strumigenys guttulata, from Queensland, Australia, is very similar to horvathi and the two may eventually prove to be con specific. For the present material representing these two nominal forms separate on differences in sculpture because in guttulata the postpetiole disc, as well as the entire side of the alitrunk is reticulate-punctate.

Brown (1973c) pointed out that because of the variation he observed he suspected that horvathi may include more than one sibling species. To the present not enough material has been amassed to analyse the situation properly.

Brown (1973) - There is some variation, both among and within series, in width of propodeal lamellae, as well as in the number of erect hairs on nodes and gaster. A large-sized Busu River series (No. 886) is dark in color, from deep reddish brown to chocolate, while the smaller sympatric series are generally lighter, yellowish-to-medium-ferruginous. The mid-mountain (Ebabaang) samples are intermediate in color.

The female is so different from the accompanying workers in mandible form and body pilosity that it might have been considered a separate species were it not for the exclusive female-worker association holding in two separate nest series. Their degenerate mandibles and fine pilosity indicate a good possibility that S. horvathi females may be temporary social parasites, perhaps in the nests of some other Strumigenys species. (It would be interesting to see whether the females of the other worker size classes are like these except for size).

Distribution based on Regional Taxon Lists
Indo-Australian Region: Indonesia, New Guinea.

Nomenclature

 *  horvathi. Strumigenys horvathi Emery, 1897c: 577, pl. 14, fig. 8 (w.) NEW GUINEA. Brown, 1973c: 261 (q.). See also: Bolton, 2000: 833.

Worker
Bolton (2000) - TL 2.0-2.4, HL 0.55-0.66, HW 0.43-0.52, CI 75-79, ML 0.22-0.26, MI 35-40, SL 0.28-0.32, SI 61-65, PW 0.24-0.28, AL 0.52-0.64 (8 measured).

Dorsal surfaces of head and promesonotum densely clothed with scale-like to suborbicular ground-pilosity, the hairs strongly curved and closely applied to the surface. Posteriorly on mesonotum these hairs are more elevated than elsewhere; there are no erect hairs anywhere on the cephalic and alitrunk dorsa. Pronotal humeral hairs absent. First gastral tergite with numerous erect stiff hairs that are slightly thickened or flattened apically, or weakly remiform. Dorsum of head and alitrunk reticulate-punctate but sculpture much concealed by ground-pilosity. Side of alitrunk with a smooth area on katepisternum and usually also on side of pronotum. Disc of postpetiole apparently unsculptured, or at most weakly shagreenate, when clean.

Queen
Brown (1973) - (Smaller Busu River form, sample nos. 926 and 1009, both alate and dealate; one individual measured from each series): TL 2.4; HL 0.53, 0.55; HW 0.43, 0.44; ML 0.17; WL 0.60; scape L 0.29, 0.30; forewing L (smaller specimen) ca. 1.8mm; CI 81, 80; MI 32, 31.

Mandibles very short, the inner lamellae extending only a little more than half their exposed length. Apical and preapical teeth short, the dorsal apical tooth oblique; intercalary denticles one or two, indistinct.

Ground pilosity of head, trunk, and appendages much finer (not orbicular) and comparatively inconspicuous. Head and trunk with long, fine flagelliform hairs in bilaterally paired positions: 1 pair on vertex, 1 pair on posterior occipital lobes, 3 pairs on lateral borders of occiput, 2 pairs on anterior scape borders (2 hairs on each scape), several pairs on gular surface, 4-5 shorter pairs on trunk, a few scattered over the legs; about 3 fine flagellate pairs on petiolar node, 3-4 pairs on postpetiole, and roughly 60 hairs on both surfaces of the gaster replace the stout clavate or remiform hairs of the worker.

Otherwise, the queen differs from the co-nidal workers only in the usual ways. The middle sides of the trunk are smooth and shining. Wings with greatly reduced venation; forewing with only R + Sc, Sc, St, 2r and Rsfl clearly demarcated; Rs beyond 2r, Mfl and CuA are present in shadow condition. The only winged queen was found in colony no. 1009 (Busu River) on May 11, 1955, together with at least one dealate.

Type Material
Bolton (2000) - Holotype worker, PAPUA NEW GUINEA: Hansemann Mts (L. Biro) [examined].

References based on Global Ant Biodiversity Informatics

 * Bolton, B. 2000. The Ant Tribe Dacetini. Memoirs of the American Entomological Institute 65
 * Brown W. L., Jr. 1973. The Indo-Australian species of the ant genus Strumigenys: groups of horvathi, mayri and wallacei. Pac. Insects 15: 259-269.
 * Brown W. L., Jr. 1973. The Indo-Australian species of the ant genus Strumigenys: groups of horvathi, mayri and wallacei. Pacific Insects 15: 259-269.
 * CSIRO Collection
 * Chapman, J. W., and Capco, S. R. 1951. Check list of the ants (Hymenoptera: Formicidae) of Asia. Monogr. Inst. Sci. Technol. Manila 1: 1-327
 * Emery C. 1897. Formicidarum species novae vel minus cognitae in collectione Musaei Nationalis Hungarici quas in Nova-Guinea, colonia germanica, collegit L. Biró. Természetrajzi Füzetek 20: 571-599.
 * Janda M., G. D. Alpert, M. L. Borowiec, E. P. Economo, P. Klimes, E. Sarnat, and S. O. Shattuck. 2011. Cheklist of ants described and recorded from New Guinea and associated islands. Available on http://www.newguineants.org/. Accessed on 24th Feb. 2011.
 * Klimes P., P. Fibich, C. Idigel, and M. Rimandai. 2015. Disentangling the diversity of arboreal ant communities in tropical forest trees. PLoS ONE 10(2): e0117853. doi:10.1371/journal.pone.0117853
 * Snelling R. R. 1998. Insect Part 1: The social Hymenoptera. In Mack A. L. (Ed.) A Biological Assessment of the Lakekamu Basin, Papua New Guinea, RAP 9. 189 ppages
 * Viehmeyer H. 1912. Ameisen aus Deutsch Neuguinea gesammelt von Dr. O. Schlaginhaufen. Nebst einem Verzeichnisse der papuanischen Arten. Abhandlungen und Berichte des Königlichen Zoologischen und Anthropologische-Ethnographischen Museums zu Dresden 14: 1-26.