Temnothorax barrettoi Hamer & Guénard, 2023

Hamer, Matthew T., Lee, Roger H. & Guénard, Benoit, 2023, First record of the genus Temnothorax Mayr, 1861 (Formicidae: Myrmicinae) in Hong Kong, with descriptions of two new species, European Journal of Taxonomy 879 (1), pp. 116-135 : 119-124

Temnothorax barrettoi Hamer & Guénard sp. nov.

urn:lsid:zoobank.org:act:0FD13BA5-2E10-4CF1-A1EC-CC6E12311736

Figs 1–2 , 5

Diagnosis

Lateral head margin in full face view subparallel; clypeus with longitudinal carinae only in the anterior half; head dorsum with areolate-rugose sculpture; scapes of medium length, not reaching occipital head margin; promesonotum convex; mesosoma dorsal margin straight in lateral view; metanotal groove absent; head, mesosoma and gaster covered in erect, stout setae.

Etymology

The name ‛ barrettoi ’ is a masculine noun in the genitive case. Named after the stewards of Tai Po Kau Headland, the Barretto family, who have cared for the headland for several generations and kindly provided us sampling access to their property. Their determined ecological conservation efforts for the site and Hong Kong in general are an example to all.

Material examined

Holotype CHINA • worker; Hong Kong SAR, New Territories (Tai Po), Tai Po Kau Headland; 22°26′06.0″ N, 114°11′35.52″ E; 70 m a.s.l.; 19–26 Aug. 2022; Matthew T. Hamer and André Ibáñez leg.; leaf litter collected in a line transect of 5 samples each 0.25 m² with silftrate extracted in a Winkler for 7 days; ZRC ANTWEB1010973 [TPK1T2W1-21].

Description

MEASUREMENTS. Holotype: CL 0.525; CW 0.486; CWb 0.440; SL 0.331; WL 0.641; SPST 0.271; PEL 0.28; PPL 0.137; PEH 0.18; PPH 0.17; PW 0.333; SPBA 0.187; SPTI 0.227; PEW 0.132; PPW 0.216; ATL 0.658; HS 0.483; SI 75.2; CI 83.8; SBI 42.5; PSI 42.3; PWI 163.6; PLI 204.4; TL 2.241

HEAD. In full face view, head longer than broad (CI 83.8), reaching maximum width just anterior to occipital corner curvature. Occipital corners rounded; occipital margin broadly convex. Lateral margins of head subparallel, diverging from anterior head margin in full face view. Clypeus widely inserted between antennal lobes; anterior margin strongly convex and angulate medially. In lateral view, clypeus projecting anteriorly forming a shelf above mandibles. In full face view, epistomal sulcus indistinct, slight cuticular impression only. Mandible broadly triangular; masticatory margin with five teeth; apical most tooth larger than preceding teeth. Frontal carina extending just posterior of frontal lobes; thin costae extends beyond forming dorsal scrobe margin feebly impressed anterior to occiput where they terminate. Frontal lobes present; projecting dorso-laterally and obscuring antennal condyle in full face view; anterior portion of frontal lobe broadly circular. Antenna with 12 segments terminating in an incrassate three-segmented club: apical segment longer and broader than following segments. Scape of medium length (SI 75.2), terminating before posterior corners of the head. Eye convex; located medially on head and extending laterally beyond the cephalic capsule. In lateral view, eyes composed of 7–8 ommatidia across the longest width. Scrobe present but feebly impressed. In dorsal view, occipital carina present.

MESOSOMA. Mesosoma in dorsal view widest at the anterior most portion of pronotum. In dorsal view, pronotum broadly convex anteriorly; humeri rounded. Mesosoma tapering posteriorly, reaching a minimum width at the anterior part to propodeum where is subsequently expands outwards but less than maximum pronotum width. Promesonotal suture absent dorsally but present laterally; metanotal groove absent. In lateral view, promesonotum convex, remaining mesosoma dorsal margin straight; anterior of propodeum with small protuberance; propodeal spiracle circular; propodeal lobe round; propodeal spines well-developed, longer than the distance between their bases (SPST 0.271; SBPA 0.187). In dorsal view, spines initially diverge postero-laterally and abruptly curving to become parallel apically, forming a ‘U’ shape. In lateral view, spines acute, thin and slightly downcurved, not beyond mesosoma lateral outline and acute. In lateral view, propodeal declivity subtly concave.

METASOMA. In lateral view, petiole longer than high; anterior face of petiole distinctly longer than posterior face; postpetiole short, its dorsal margin convex, with lateral carina. In dorsal view, postpetiole distinctly wider than long, widest in anterior third; at its widest point, postpetiole margins meeting at a subtlety obtuse angle; lateral margins converging posteriorly in dorsal view. Gaster wider than postpetiole anteriorly in dorsal view; first gastral tergite long, as long as mesosoma; anterolateral corners obtusely angled. Basigastral costulae present extending ¹/₆ of gaster.

SETAE. In full face view, mandible dorsum with well-spaced sub-decumbent pilosity. Anterior clypeal margin with two long and tapering setae either side of clypeal median; several sub-erect setae present on anterior clypeal margin, directed towards clypeal median; clypeal dorsum with many erect and stout setae. Cephalic dorsum as well as occiput also with many stout and erect setae which arise from within areolae formed by the surface rugosities (see sculpturing); erect setae arise along frontal carina, roughly spaced roughly equidistant. Scapes and subsequent antennal segments with sub-decumbent to semi-erected pilosity only. In lateral view, ventral part of head with erect to semi-erect pilosity, noticeably different to stout-erect hairs on cephalic dorsum. Mesosoma, with long, erect setae arranged in series of transverse rows; base of propodeal spines also with a single pair of setae. Posterior face of petiole dorsum with a single pair of long erect setae, directed postero-dorsally. Postpetiole with erect setae of varying lengths, dorsally with short, erect setae and laterally with longer setae, in particular a pair of setae in dorsal view arising from area of maximum width of postpetiole. Numerous, short and appressed pubescence present on posterior post petiole surface. Gastral tergite with numerous erect stout setae arranged in loose rows; setae of varying lengths but are particularly long in posterior fifth. Setae on subsequent tergites not visible.

SCULPTURE. Mandibles smooth, other than setae insertions. Majority of clypeus dorsum smooth other than short, longitudinal carinae that begin at the clypeal anterior border. Dorsum of head from clypeus to posterior head corners areolate-rugose. Head laterally also with areolate-rugose sculpturing. Scrobe in lateral view punctate, noticeably different to the sculpture of head dorsum and surrounding lateral sculpture. Pronotum dorsum areolate-rugose, with rugosities subtly more embossed than on head dorsum. Remaining dorsal mesonotum and propodeum more indistinctly rugose, lacking dense areolae. The mesonotum with underlying punctae within areolae, which eventually merges into the punctuate propodeal declivity. The mesonotum with underlying punctae within areolae. Posterior mesonotum punctuation merges into the punctuate propodeal declivity. Lateral pronotum densely punctuate overlain with faint rugosities; mesopleuron also punctuate but with less dense and with larger punctae; the space between punctae distinctly larger. Metapleuron with more pronounced rugosities; punctuation faint. Ventral metapleuron and metapleural gland bulla with several distinct carinae. Propodeum laterally, dorsally, and posteriorly (= declivital surface) densely punctuate; punctae small. Petiole dorsally and laterally punctate.Postpetiole with punctae overlain by faint areolate-rugose sculpturing both dorsally and laterally. Anterior area of gaster with basigastral costulae extending ¹/₆ of the surface length. Remaining gaster comparatively smooth and shining, with faint micro-reticulations at high magnifications alongside setae punctation. Sculpture on subsequent tergites not visible.

COLOUR. Core body concolourous ochreous yellow, appendages conspicuously lighter yellow. Setae across whole of body yellowish white.

Comments

Temnothorax barrettoi sp. nov. would key out to T. zhejiangensis Zhou et al., 2010 within Zhou et al. (2010) and shares several morphological characters. Such characters include the presence of erect setae on the mesosomal dorsum; a pair of long slightly downcurved propodeal spines; humeri rounded in dorsal view; a short petiole peduncle and a petiole that is longer than high. However, a series of substantially and categorically differing morphological characters are present that delimit both species well even without access to type material of T. zhejiangensis . Though our study has this limitation, we justify describing this specimen from Hong Kong as new to science due the considerable uniqueness of the qualitative characters below in comparison to it nearest morphological congeneric species ( T. zhejiangensis ). Such unique characters include the dorsal head sculpture, being distinctly areolate-rugose in T. barrettoi rather than densely punctate in T. zhejiangensis . Punctuae are entirely absent on the dorsal head sculpturing of T. barrettoi and the areolate-rugose sculpturing is unique within Chinese Temnothorax ; the head sculpturing in T. zhejiangensis also has “fine striations indistinct but present on frons” ( Zhou et al. 2010), striations are entirely absent on the head of T. barrettoi ; the sculpture of the mesosoma dorsum also differs with T. zhejiangensis being “densely punctuate” whereas the sculpture in T. barrettoi is more complex, grading from areolate-rugose anteriorly to more rugose posteriorly, with a gradual increase in punctuation towards the propodeum but not only densely punctuate throughout like T. zhejiangensis ; the lateral head margins are subparallel in T. barrettoi , converging anteriorly and at the occipital corners, whereas the head margins of T. zhejiangensis are weakly convex throughout; the scapes are shorter and distinctly fail to reach the occipital border in T. barrettoi (SL 0.331) but are long and reach the occipital border in T. zhejiangensis (SL 0.39–0.48); in lateral view T. barrettoi has a flat mesosoma dorsum rather than a convex mesosoma dorsum in T. zhejiangensis . Temnothorax barrettoi may also be mistaken for T. ruginosus Zhou et al. (2010) . However, both species can be differentiated by the smaller size of T. barrettoi being less than half the size of T. ruginosus ( T. barrettoi WL 0.641; T. ruginosus WL (ML in Zhou et al. 2010) 1.80–1.84), as well as the head dorsum sculpture being areolate-rugose rather than coarsely longitudinally rugose in T. ruginosus . Moreover, the lateral head margins are subparallel converging at occipital corners in T. barrettoi but are convex throughout in T. ruginosus .

Here, we provide an exhaustive description and numerous high-resolution images of T. barrettoi sp. nov. for workers on Southeast Asian Temnothorax to consult in the future. We believe further differing characters are likely present between T. barrettoi and T. zhejinagensis but due to rather limited image quality and non-exhaustive species descriptions within Zhou et al. (2010) we judged these characters too speculative to include our delimitation. These speculative differing characters are as follows; form of the clypeal carinae, presence or absence of standing hairs on the clypeus, presence or absence of basigastral costulae, differing lengths of the terminal funicular segments and the differing shape of the petiolar node. All speculative character should be checked against T. ruginosus as well. Species descriptions and images of species of Temnothorax outside of mainland China were also reviewed but no species of Temnothorax resembled this specimen in terms of morphological characters as did T. ruginosus and T. zhejiangensis . Although the lack of additional material makes it impossible to examine any intraspecific variation, we believe that the characters (particularly the cephalic sculpture) here are fundamentally and categorically different enough to not show enough variation to overlap with other T. zhejiangensis or T. ruginosus .

It was initially thought that this specimen might be a Vombisidris Bolton, 1991 , due to the superficial resemblance with V. freyae General, 2020 , a species known from the Philippines. Closer examination showed an alternative dental array and the absence of a subocular groove. The high similarity (at least superficially) between this specimen and V. freyae however are initially convincing. Both species share the same head shape, eye positioning and type of sculpture (particularly on the head dorsum), as well as the numerous stout and erect setae across head, mesosoma and metasoma dorsum. Due to the absence of apomorphic characters encountered in Vombisidris , such as the peculiar dental composition and subocular groove, we resulted in the determination of Temnothorax for this specimen instead.

Natural history

Temnothorax barrettoi sp. nov. was collected from Tai Po Kau Headland, a Site of Special Conservation Interest owing to the presence of natural lowland coastal woodland, which has had a long history of post- World War II reforestation with minimal human disturbance ( Kendrick & Barretto 2006). Moreover, the presence of an old pre-war Feng Shui relict woodland also makes the site unique due to the long history of human disturbance elsewhere in Hong Kong ( Kendrick & Barretto 2006). One worker of T. barrettoi was found in a leaf litter sample within a patch of secondary forest approximately 250 meters away from the location of the relict forest. Further sampling using winkler extractors and vegetation beating was conducted within the collection site to acquire further specimens of T. barrettoi sp. nov. but resulted in no additional specimens. More information of the site can be found in Kendrick & Barretto (2006).

Figures

Fig. 1. Temnothorax barrettoi Hamer & Guénard sp. nov., holotype (ANTWEB1010973). A. Lateral view. B. Dorsal view. C. Full face view.

Fig. 2. Temnothorax barrettoi Hamer & Guénard sp. nov., holotype (ANTWEB1010973), morphological characters. A. Petiole and postpetiole in lateral view. B. Petiole and postpetiole in dorsal view. C. Mesosoma in dorsal view. D. First gastral tergite in dorsal view.

Fig. 5. Distribution map of Temnothorax Mayr, 1861 records from Hong Kong. The darker the green areas, the greater the tree canopy cover.