Strumigenys mitis

A rainforest species that is typically found in litter-samples. In Hong Kong, although this species is not among the most commonly collected, it was found in a wide range of habitats and elevation, including grasslands, shrublands, tree plantations (e.g. L. confertus), and secondary forest at elevation ranging from 70 to 809m (Tang et al., 2019). Colonies apparently can be relatively small in size with about 50 individuals (Mezger and Pfeiffer 2008).

Identification
Bharti & Akbar (2013) - The only member of the Strumigenys mitis-group. This small slender species is very widely distributed in the Oriental and Malesian regions. The species is easily recognized by its dorsal surfaces of middle and hind tibiae without laterally projecting long hairs anterior clypeal margin convex. Pronotal humeral hair absent. First gastral tergite without standing hairs. Base of first gastral sternite without spongiform tissue. Lateral clypeal margins without projecting hairs. With head in full-face view dorsolateral margin of occipital lobe without projecting hairs. It is one of the most commonly encountered members of the genus in Winkler bag samples made in these areas. A very complex species group with great variations, gyne polymorphism and even suspected social parasitism (Bolton, 2000).

Distribution based on Regional Taxon Lists
Indo-Australian Region: Brunei Darussalam, Indonesia, Malaysia, New Guinea, Philippines. Oriental Region: India, Thailand, Vietnam. Palaearctic Region: China.

Nomenclature

 *  mitis. Pyramica mitis Brown, in Bolton, 2000: 442, figs. 267, 290 (w.q.) PHILIPPINES. Combination in Strumigenys: Baroni Urbani & De Andrade, 2007: 124

Worker
Holotype. TL 1.9, HL 0.49, HW 0.33, CI 67, ML 0.09, MI 18, SL 0.25, SI 75, AL 0.52. Head in full-face view slender and, with the closed mandibles, cuneiform. Dorsolateral margins of head rounded at their maximum width. From its widest part the sides of the head converge in an almost straight outline to the mandibles. In profile the head depressed and its dorsal outline nearly flat, only very feebly convex; the clypeal and mandibular dorsal surfaces continue the line. Eyes visible in full-face view, their outer margins projecting beyond the dorsolateral margins of the head. Cephalic dorsum finely and densely reticulate-punctate. Pronotum in dorsal view elliptical anteriorly, the humeri not angulate. Metanotal groove absent. Dorsal alitrunk reticulate-punctate but sides mostly smooth and shining. Petiole node in profile narrowly rounded, in dorsal view slightly broader than long and flanked by conspicuous lateral spongiform lobes. Disc of postpetiole transverse, enveloped in voluminous spongiform lobes. Dorsum of petiole node weakly reticulate-punctate; disc of postpetiole mostly smooth but with some very fine obscure sculpture anteriorly. Basigastral costulae fine and numerous, behind them the tergite smooth and shining.

Paratypes. TL 1.5-1.9, HL 0.43-0.49, HW 0.29-0.33, CI 65-70, ML 0.05-0.09, MI 12-18, SL 0.20-0.25, AL 0.41-0.52 (14 measured).

Dimensions of non-paratypic workers. TL 1.4-1.9, HL 0.39-0.51, HW 0.28-0.35, CI 65-75, ML 0.05-0.09, MI 12-20, SL 0.18-0.25, SI 63-75, PW 0.18-0.22, AL 0.38-0.52 (40 measured).

Queen
Based on the workers only one species is currently recognised in this group, distributed over a vast range. I am sure that this does not reflect the true taxonomic situation. Eleven series of mitis workers have at least one queen in association, and this caste shows so much variation, in characters that are usually very important and stable in Pyramica, that I am convinced that several species are compounded here. However, as only 16 queens in total are known, and variation is so marked, no definite statements about what constitute real species can yet be made. The sorting of this tangle is made more difficult as I suspect that some degree of queen polymorphism may also be present, as may at least one social parasite. As the workers are so conservative in their features real characters that segregate them into species cannot be estimated until more is known about character stability in the queens. And this cannot be estimated until more series with queens and workers in association have been amassed.

The currently available queens can be divided roughly into five morphs, as discussed below. This segregation is provisional. I do not claim that the characters utilised represent any formal taxonomic rank; there is not enough material to substantiate such a claim.

Queen morph A (1 specimen: Sulawesi; in ANIC).

Head and dorsal alitrunk glassy smooth. Entire dorsum of head very densely clothed with mostly straight suberect hairs. Ventral surface of head with abundant similar hairs and with several pairs of much longer sinuate to flagellate hairs. All other queens (morphs B-E) have strongly sculptured head and dorsal alitrunk and lack this form of cephalic pilosity.

Queen morph B (4 specimens: West Malaysia; in BMNH).

The pronotal humeri do not have flagellate or elongate stiff filiform hairs present. All other samples possess such hairs (flagellate in morphs C and E, stiff and filiform in morphs A and D).

Queen morph C (2 specimens: Sarawak; in BMNH and MCZ).

With the head in full-face view the lateral margin of the occipital lobe does not have long simple hairs that project from the margin and curve anteriorly. Such hairs are also absent in morph B but present in morphs D and E.

Queen morph D (1 specimen: Bali; in AMNH)

Pronotal humeri with stiff filiform hairs. Lateral margin of occipital lobe with many short curved simple hairs. Leading edge of scape and all segments of legs with abundant suberect stiff projecting short hairs. Entire dorsum of head and body very densely clothed with short stiff suberect to erect hairs.

Queen morph E (8 specimens: Philippines, Singapore, West Malaysia, Sabah, Java, Sulawesi; in BMNH and MCZ).

Pronotal humeri with flagellate hairs. Lateral margin of occipital lobe with 1-2 long, anteriorly curved fine simple hairs present.

No two series within morph E have queens that are exactly alike. For instance specimens from Java (2; in BMNH and MCZ) and Sulawesi (1; in BMNH) are small (worker HW 0.33-0.34, queen HW 0.36-0.40) and have numerous flagellate hairs arising from the dorsal mesoscutum. These are lacking or sparse in other morph E specimens. The Java queens have dense, sharply defined basigastral costulae whereas the Sulawesi queen has them very faint, short and poorly defined. None of them has flagellate hairs arising from the dorsal (outer) surface of the hind tibia. None of them has long straight fine hairs projecting forward from the leading edge of the scape.

Queens from Singapore (1; in MCZ) and Philippines (2; in MCZ) are also small (worker HW 0.30-0.32, queen HW 0.32-0.34), but they have long projecting hairs at the midlength of the dorsal (outer) surface of the hind tibia and on the leading edge of the scape; such hairs are more numerous in the former than in the latter. Basigastral costulae are sharply defined, long and directed straight backward.

A projecting tibial hair occurs in a large queen from Sabah (1; in BMNH; worker HW 0.32, queen HW 0.37), but not in an even larger specimen from West Malaysia (1; in BMNH; worker HW 0.34, queen HW 0.40). Both lack projecting hairs on the scape and in both the basigastral costulae are feebly developed, but in the West Malaysian queen they are oblique, slanting toward the midline. This specimen is also the only one that shows sculpture on the postpetiole disc, though the disc in associated workers remains smooth.

Type Material
Holotype worker, Philippines: Luzon, Lagunas Prov., Mt Makiling, vi.1966, rain forest, berlesate (K. Dumont & R. Morse).

Paratypes. Numerous workers and 3 queens (dealate) with same data as holotype and some with same data but v. 1968 (R.A. Morse) (MCZ,, ).