Two new myrmecophilous species of the supertribes Clavigeritae and Batrisitae are described from Yunnan, Southwest China: Diartiger jiquanyui sp. nov. associated with Lasius Fabricius ants, and Myrmicophila yulong sp. nov. associated with Myrmica Latreille ants. Both species are compared with and separated from related congeners, and images of their habitus and major diagnostic features are provided.
Our knowledge of the taxonomic and ecological diversity of myrmecophilous Pselaphinae in China has been continuously increasing during the past decade. A number of new genera and dozens of new species belonging to the supertribes Euplectitae, Goniaceritae, Pselaphitae, and especially Clavigeritae and Batrisitae were described from various areas of the country (e.g., Yin et al., 2010a-c, 2011a-c, 2012a-d, 2013, 2015a, b; Yin & Li, 2012, 2013a-c, 2014, 2015; Zhao et al., 2010; Jiang & Yin, 2016, 2017; Yin, 2017a, b, 2018a, b; Yin & Lin, 2020; Yin & He, 2020). So far, the Chinese fauna of the obligate myrmecophilous supertribe Clavigeritae is represented by seven genera and 15 species, with the genus Diartiger Sharp being the most diverse group, containing seven species (Nomura, 1997; Li et al., 2019; Yin & He, 2020). In China, members of Diartiger are most commonly found in the association with Lasius ants, and occasionally, also with Ectomomyrmex ants which often nest under stones or in decomposing logs. On the other hand, among the many recently described myrmecophiles belonging to the supertribe Batrisitae, the genus Myrmicophila Yin & Li is of particular interest regarding its distributional pattern and biology. Currently there are two species confined to the southwestern Chinese provinces of Yunnan and Xizang (Yin et al., 2011b; Yin, 2021), which were collected only with Myrmica ants. In May 2021 our colleague Quan-Yu Ji conducted a field trip in Yunnan, and collected a small series of pselaphines directly from ant nests in two localities. An examination of this material revealed two new species of Diartiger and Myrmicophila, which are described here.
MATERIAL AND METHODS
The type material of the new species described in this paper is deposited in the Insect Collection of Shanghai Normal University, Shanghai, China (SNUC). The text of the specimen label is quoted verbatim in quotation marks (‘’).
Dissected parts were preserved in Euparal on plastic slides that were placed on the same pin with the specimen. The habitus images of the beetle and host ant, as well as the ant's full-face image was taken using a Canon 5D Mark III camera in conjunction with a Canon MP-E 65 mm f/2.8 1-5X Macro Lens, and a Canon MT-24EX Macro Twin Lite Flash was used as the light source. Images of the morphological details were produced using a Canon G9 camera mounted to an Olympus CX31 microscope under reflected or transmitted light. Zerene Stacker (version 1.04) was used for image stacking. All images were optimized and grouped into plates using Adobe Photoshop CC 2018.
The abdominal tergites and sternites are numbered following Chandler (2001) in Arabic (starting from the first visible segment) and Roman (reflecting true morphological position) numerals, e.g., tergite 1 (IV), or sternite 1 (III).
Type material: HOLOTYPE; ♂; CHINA, ‘China: Yunnan, Deqin County, Yubeng Vill., 28°25′28.40″N, 98°48′38.89″E, ca. 2740 m, 8.iv.2021, Q.-Y. Ji leg., 云南德钦县云岭乡雨崩村’ (SNUC). PARATYTYPE; 1 ♂; CHINA, same collection data as of holotype (SNUC).
Diagnosis: Body length approximately 2.4 mm. Anterior margin of clypeus broadly rounded. Antennomere 4 2.3 times as long as 3. Mesotrochanter with large curved ventral spine; mesofemur with blade-like ventral projection split into two lobes; mesotibia with row of denticles along mesal margin. Median lobe of aedeagus clearly separated into apical and basal parts.
Description: Male (Fig. 1A). Body length (combined length of head, pronotum, elytra and abdomen) 2.41-2.42 mm, colour reddish-brown. Head (Fig. 2A) elongate, length from anterior margin of clypeus to posterior margin of head (excluding neck region) 0.51-0.52 mm, width across eyes 0.29 mm; clypeus with broadly-rounded anterior margin; each eye composed of approximately 25 facets; antenna clubbed, with short antennomere and 2 and elongate 3 and 4 (Fig. 2B), length of antennomere 2 0.05-0.06 mm, 3 0.16-0.17 mm, 4 0.38-0.39 mm; antennomere 4 longest, narrowed at base and broadly apically, truncate at apex, approximately 2.3 times as long as 3; distinct gular foveae (posterior tentorial pits) close, in shared impression.
Pronotum (Fig. 2A) subglobose, surface roughly punctate, approximately as long as wide, length along midline 0.44-0.45 mm, maximum width 0.43-0.44 mm; widest at middle; with distinct median antebasal impression.
Elytra much broader than long (Fig. 1A), length along suture 0.64-0.65 mm, maximum width 0.86-0.87 mm; with linear microsculpture on disc, and long setae along posterior margin; posterolateral margins with sub-triangular tufts of setae (Fig. 2C). Metathoracic wings fully-developed. Prosternum (Fig. 2D) roughly sculptured medially; mesoventrite (Fig. 2D) with short intercoxal ridge, metaventrite (Fig. 2D) convex admesally, both ventrites with dense, thick setae along midline, with distinct linear microsculpture laterally.
Fore and hind leg simple; middle leg (Fig. 2E) greatly modified, mesotrochanter with long, sharp, and curved ventral spine, mesofemur with broad blade-like projection separated into two lobes, mesotibia moderately expanded at basal 1/3, with row of denticles of various size along mesal margin.
Abdomen large, slightly broader than long, length along midline 0.80-0.82 mm, maximum width 0.84-0.87 mm; composite tergite broadly and deeply concave mediobasally, with ball of trichomes (Fig. 2C) at basolateral region, first pair of paratergites (Fig. 2C) with linear trichomes.
Aedeagus (Fig. 2F, G) strongly sclerotized, length 0.35 mm; basal capsule with large basoventral projection, median lobe gradually narrowing apically, with small membranous structure at apex.
Comparative notes: Diartiger jiquanyui sp. nov. differs from all known congeners from China by the broad, blade-shaped and deeply split projection of mesofemora, rowed denticles along the mesal margin of mesotibiae, as well as the median lobe of aedeagus clearly separated into two parts. In China, only D. songxiaobini (Yin & Li) from West Tianmu Mountain, Zhejiang, eastern China has a similarly structured aedeagus (Yin et al., 2010b), but in the latter species the forms of the spines of the middle legs are quite different.
Distribution: China: Yunnan.
Host ant: Lasius sp. (Fig. 4A-C).
Etymology: The new species is named after Quan-Yu Ji, the collector of the holotype.
Type material: HOLOTYPE; ♂; CHINA, ‘China: Yunnan, Lijiang City, Yulong Snow Mt., Lanyue Valley, 27°7′46.49″N, 100°14′30.14″E, ca. 2900 m, 29.iii.2021, Q.-Y. Ji leg., 玉龙雪山蓝月谷’ (SNUC). PARATYPE; 1 ♀; CHINA, same collection data as of holotype (SNUC).
Diagnosis: Body length slightly over 3.5 mm. Antennomere 5 greatly extended mesally, 6 moderately transverse, 8-10 moniliform, successively broader. Mesotibia with distinct apical spur, slightly sinuate along mesal margins; metafemur broadly expanded on dorsal margins. Aedeagus with median lobe greatly extended apically and strongly curved ventrally.
Description: Male (Fig. 1B). Habitus stout, length (combined length of head, pronotum, elytra and abdomen) 3.66 mm, colour uniformly reddish-brown; dorsal surface of whole body finely punctate, with short recumbent setae on elytra and abdomen slightly denser than those on head and pronotum.
Head (Fig. 3A) sub-rectangular at base, length from anterior margin of clypeus to posterior margin of head (excluding neck region) 0.66 mm, width across eyes 0.69 mm; distinct asetose vertexal foveae at level of posterior margin of eyes; mediobasal ridge extending from posterior margin of head towards approximately posterior 1/3 of head length; frons broadly and shallowly impressed between moderately raised antennal tubercles; postocular margin angularly rounded; eyes moderately prominent, each composed of approximately 50 facets. Antenna elongate, lacking distinct club, length 1.70 mm; antennomere 1 (scape) thick, with deep dorso-ventral notch at apex, 2 and 3 much narrower than 1, elongate, successively broader and longer, 4 broader than 3, slightly transverse, 5 (Fig. 3B) transverse, strongly expanded on mesal margin, 6-10 moniliform, 6 broader than 7, 7 and 8 of similar width, 9 broader than 8, 9-10 gradually broader, 11 subconical, approximately as broad as 10. Gular area with foveae (posterior tentorial pits) close to each other, in shared oval impression, with thin gular ridge extending to mouthparts.
Pronotum (Fig. 3A) sub-globose, widest at anterior 2/5, length along midline 0.7 mm, maximum width 0.72 mm, with round lateral margins gradually narrowing from broadest point towards base and apex, anterior and posterior margin almost straight; with short median longitudinal sulcus at base, and distinct asetose lateral antebasal foveae.
Elytra broader than long, length along suture 1.07 mm, maximum width 1.34 mm, each elytron with three large, nude basal foveae, sutural stria complete, with short and shallow discal stria, lacking marginal stria. Metaventrite strongly convex lateral to midline.
Abdomen slightly broader than long, widest at tergite 1 (IV), length along midline 1.23 mm, maximum width 1.33 mm. Tergite 1 (IV) at mid-length slightly longer than 2 (V), tergites 1 (IV) to 3 (VI) successively shorter, tergite 4 (VII) approximately as long as tergite 2 (V).
Aedeagus (Fig. 2E, F) well-sclerotized, length 0.75 mm; median lobe with large, transverse basal capsule and foramen; ventral and dorsal lobe each composed of flattened, apically pointed and curved sclerites; parameres paired and weakly-sclerotized, attached to ventral side of capsule.
Female. External morphology similar to male; antenna shorter and unmodified; mesotibia lacking spur at apex, metafemur lacking expansion. Measurements (as for male): body length 3.59 mm, length/width of head 0.65/0.71 mm, pronotum 0.73/0.75 mm, elytra 1.35/1.04 mm, abdomen 1.17/1.37 mm, length of antenna 1.62 mm, each eye with approximately 40 facets.
Comparative notes: Two species of Myrmicophila have been known: M. tangliangi Yin & Li from Yunnan (Yin et al., 2011b) and M. motuoensis Yin from Xizang (Yin, 2021), each was collected from nests of a different Myrmica species. The new species is in general similar to M. tangliangi and M. motuoensis by sharing identical positions of the male sexual characters on antennomeres 5 and metafemora, indicating close relationships between these three species. However, a number of characters, both external and internal, support the status of a distinct species of the population from Yulong Mountain. The development of the male antennomeres of M. yulong sp. nov. appears to be intermediate between M. tangliangi and M. motuoensis, the antennomeres 5-7 of the new species are relatively much broader than M. tangliangi, but narrower than those of M. motuoensis; the mesotibia is slightly sinuate along the mesal margin, but they are evenly slightly curved in M. tangliangi and M. motuoensis; the apical spur of mesotibia is much larger than that of M. motuoensis, and of similar size but of a different shape as in M. tangliangi (triangular, blade-like); and the median lobe of the aedeagus is more greatly extended apically and more strongly curved ventrally than the other two species. In addition, the validation of the new species is also supported by ecological evidence. The ant host of M. yulong sp. nov. is morphologically more similar to that of M. motuoensis from Motuo, Xizang, but apparently represents a different species by the smaller body size, and presence of a distinct reversed V-shaped sulcus on the pronotal disc (sulcus vague in Myrmica sp. from Muotuo).
Distribution: China: Yunnan.
Host ant: Myrmica sp. (Fig. 4D-F).
Etymology: The new species is named after its type locality, the Yulong Snow Mountain.
We thank Quan-Yu Ji (Hebei University, Hebei, China) for the generous gift of the material. Zhi-Lin Chen (Guangxi Normal University, Guilin, Guangxi, China) provided identifications of the host ants. Two anonymous reviewers commented on the draft manuscript which improved the paper. The present study was supported by the National Natural Science Foundation of China (No. 31872965), and the ‘Phosphor’ Science Foundation, Shanghai Municipal Science and Technology Commission, China (19QA1406600) awarded to ZWY.