Strumigenys sydorata

Represented by a small number of specimens, this species is rare in Hong Kong and occurs only within secondary forests and Feng Shui woods, with elevations of collection sites ranged from 15 to 170 m (Tang et al., 2019). In Sumatra, Musfira et al. (2022) found a small colony (24 individuals) nesting in a dead twig. Another small colony consisting of one dealate queen and 23 workers was collected from the leaf litter layer of disturbed forest (touristic area visited by local people), at an altitude of ca. 130 m.

Identification
Bolton (2000) - A member of the lyroessa complex in the Strumigenys lyroessa-group. Very closely related to Strumigenys arrogantia and best separated by details of mandibular structure mentioned in the key and descriptions. A small point that may be significant is that sydorata seems at most to have two pairs of erect mesonotal hairs whilst arrogantia has three such pairs. Because these hairs are frequently abraded the character is best applied only to specimens in perfect condition. For other related species see under arrogantia.

Tang et al. (2019) - Strumigenys sydorata belongs to the lyroessa-complex within the S. lyroessa-group. This species can be separated from others in this group by the presence of pronotal humeral hairs, a smooth first gastral tergite, a well-developed lamella along the propodeal declivity, and a larger preapical tooth when compared to the apicodorsal tooth on mandibles. The latter character separates it from Strumigenys arrogantia, which is slightly smaller than S. sydorata.

Distribution
The record from Hong Kong represents another important geographic extension of 900 km north-eastward in Mainland Asia, with the closest record known from Cúc Phương in Vietnam (Eguchi et al. 2011; Tang et al., 2019).

Distribution based on Regional Taxon Lists
Indo-Australian Region: Indonesia, Malaysia, Singapore. Oriental Region: Thailand, Vietnam. Palaearctic Region: China.

Nomenclature

 *  sydorata. Strumigenys sydorata Bolton, 2000: 876 (w.q.) INDONESIA (Java).

Worker
Holotype. TL 2.6, HL 0.74, HW 0.56, CI 76, ML 0.20, MI 27, SL 0.30, SI 54, PW 0.34, AL 0.70. Characters of lyroessa-complex. In profile preapical tooth of mandible stouter and more strongly developed than apicodorsal tooth. Dorsal margin of mandible, as seen in profile, appears depressed distal of preapical tooth, the gap between preapical and apicodorsal teeth represented by a cleft rather than a transverse margin. Upper scrobe margin with a row of anteriorly curved small spoon-shaped hairs. Apicoscrobal hair short, stiff and stout; dorsolateral margin posterior to this with 5-6 similarly shaped but slightly shorter projecting hairs. Cephalic dorsum with standing hairs restricted to a stubbly transverse row along the occipital margin. Pronotal humeral hair short and stiff; pronotum otherwise without standing hairs. Mesonotum with 2 pairs of remiform to apically expanded short erect hairs, located along the dorsolateral margins; anterior hair the longest. Width of lamella on propodeal declivity, at its broadest point below level of spiracle, more than half the length of the propodeal tooth. Erect hairs on first gastral tergite short and stiff, spatulate or expanded apically, distributed over the entire sclerite.

Paratypes. TL 2.4-2.6, HL 0.64-0.74, HW 0.49-0.57, CI 76-78, ML 0.18-0.21, MI 27-30, SL 0.26-0.30, SI 51-54, PW 0.28-0.35, AL 0.62-0.70 (4 measured). As holotype but posterior mesonotal hair frequently missing, probably abraded off.

Dimensions of non-paratypic workers. HL 0.66-0.76, HW 0.52-0.58, CI 74-78, ML 0.19-0.22, MI 28-29, SL 0.26-0.30, SI 50-54 (5 measured).

Determination Clarifications
This species was referred to as Strumigenys sp. 7 and sp. 9 in Bolton, 1998b: 92.

References based on Global Ant Biodiversity Informatics

 * Bolton, B. 2000. The Ant Tribe Dacetini. Memoirs of the American Entomological Institute 65
 * Eguchi K.; Bui T. V.; Yamane S. 2011. Generic synopsis of the Formicidae of Vietnam (Insecta: Hymenoptera), part I  Myrmicinae and Pseudomyrmecinae. Zootaxa 2878: 1-61.
 * Fontanilla A. M., A. Nakamura, Z. Xu, M. Cao, R. L. Kitching, Y. Tang, and C. J. Burwell. 2019. Taxonomic and functional ant diversity along tropical, subtropical, and subalpine elevational transects in southwest China. Insects 10, 128; doi:10.3390/insects10050128
 * Tang K.L., Pierce M.P., and B. Guénard. 2019. Review of the genus Strumigenys (Hymenoptera, Formicidae, Myrmicinae) in Hong Kong with the description of three new species and the addition of five native and four introduced species records. ZooKeys 831: 1-48.
 * Zryanin V. A. 2011. An eco-faunistic review of ants (Hymenoptera: Formicidae). In: Structure and functions of soil communities of a monsoon tropical forest (Cat Tien National Park, southern Vietnam) / A.V. Tiunov (Editor). – M.: KMK Scientific Press. 2011. 277 р.101-124.