Leptanilla bethyloides, Griebenow, 2024

Griebenow, Zachary, 2024, Systematic revision of the ant subfamily Leptanillinae (Hymenoptera, Formicidae), ZooKeys 1189, pp. 83-184 : 83

Leptanilla bethyloides sp. nov.

Figs 11A-C , 12

Type material.

Holotype. China - Hong Kong • 1 male; Tai Po Kau; 22.44°N, 114.18°E (estimated from Google Earth to nearest minute), 15 Jun. 1964; W. J. Voss and W. M. Hui leg.; CASENT0842864. BPBM. Paratype. China - Hong Kong • 1 male; same locality as for preceding; 2-6 Jul. 1964; L. K. and H. W. Ming leg.; light trap; CASENT0842865. BPBM.

Measurements (mm) and indices, male.

Holotype: HW = 0.27; HL = 0.32; SL = 0.10; LF2 = 0.04; EL = 0.11; EW = 0.12; WL = 0.59; MSL = 0.35; MSW = 0.23; PTW = 0.25; PTL = 0.10; PTH = 0.13; REL = 34; SI = 36; CI = 244; OI = 113; MSI = 152.38; PI = 247.52. Paratype: HW = 0.25; HL = 0.30; SL = 0.08; LF2 = 0.04; EL = 0.11; EW = 0.12; WL = 0.53; MSL = 0.31; MSW = 0.22; PTH = 0.12; REL = 35; SI = 32; CI = 219; OI = 110; MSI = 139

Description.

Cranial outline quadrate. Occiput emarginate in full-face view. Frons not produced into anterior shelf. Mandible articulated to gena; broader than long. Mandalus large, covering entire anterodorsal mandibular surface. Maxillary palp 1-merous. Clypeus anteroposteriorly reduced, not discernible in full-face view. Anterior tentorial pits not discernible. Compound eyes wider than long in profile view (OI = 110-112), posterior margin slightly emarginate, all other margins convex. Anteromedian ocellus and compound eyes not intersecting line drawn perpendicular to anteroposterior axis of cranium. Scape anteroposteriorly compressed, longer than wide (SL = 0.081-0.095 mm), shorter than anteroposterior length of compound eye; pedicel short, subcylindrical, lateral margins parallel, length 0.5 × that of scape; antennomere 3 short (LF2 = 0.037-0.039 mm), subcylindrical, length subequal to that of pedicel; flagellum submoniliform, not extending posterior to mesoscutum if folded flat over mesosoma. Pronotum and mesoscutum posteriorly prolonged. In profile view anterodorsal pronotal face diagonal to craniocaudal axis at ~45° angle, but profile of pronotum otherwise obscured by vestiture. Mesoscutal dorsum slightly convex; mesoscutum longer than broad (MSI = 139-152). Antero-admedian signum absent. Notauli absent. Parapsidal signa present, impressed. Mesoscutellum longer than tall, dorsum not lower than that of mesoscutum, posterodorsal mesoscutellar face convex, posteriorly produced, not recurved. Oblique mesopleural sulcus present, not intersecting metapectal-propodeal complex. Metapleuron distinct, transected by transverse sulcus. Metapleural gland absent. Propodeum convex in profile view, without distinct dorsal and posterior faces. Pro- and metacoxa subequal in length, metacoxa somewhat more massive; mesocoxa shorter than pro- and metacoxa. Protrochanters sphenoid in outline, distally truncate. Profemur not markedly constricted at base, anteroposteriorly compressed, incrassate; acute distal flange on posterior surface absent; arcuate medial carina absent. Protibial and profemoral length subequal; protibia not dorsoventrally compressed, without ventromedian carina; protibial comb absent; probasitarsal seta not hypertrophied. Meso- and metatibial spur formula 2b,2(1b,1p). C and Sc+R+Rs fused, tubular; 2s-rs +R+4-6 and M+Cu tubular; all other venation absent. Costal infuscation absent. Abdominal segment II anteroposteriorly compressed, broader than long in dorsal view excluding presclerites; dorsal node present, well-developed; with median dorsal excavation. Abdominal sternite II without process, planar in profile view. Presclerites of abdominal segments IV-VIII inconspicuous. Abdominal segments III-VII without tergosternal fusion. Tergosternal fusion of abdominal segment VIII-IX unknown. Abdominal tergites III-VIII not anteroposteriorly compressed, lateral margins subparallel; breadth of abdominal tergite VIII subequal to that of abdominal tergite VII in posterodorsal view. Abdominal sternite VIII anteroposteriorly compressed, visible without dissection, posterior margin entire. Abdominal sternite IX not visible without dissection. Mulceators absent. Gonopodites articulate. Gonocoxites without complete dorsomedian and ventromedian fusion; ventromedial margin of gonocoxite with lamina; apicoventral laminae absent. Gonostylus present, outline lanceolate, apex entire. Volsellae absent. Penial sclerites dorsoventrally compressed, not basally recurved, ventromedian carina extending along most of length, without lateral laminate margins. Phallotreme dorsal, concealed by gonostyli in available specimens. Somal sclerites with thick vestiture of decumbent to suberect setae, sparsest on meso- and metapleuron; setae appressed to decumbent on antennae and legs; gonostyli with similar vestiture to abdominal postsclerites, genitalia otherwise glabrous. Base of forewing costa bearing row of exceptionally long, suberect setae. Cuticle bearing piligerous punctae; sculpture otherwise absent.

Etymology.

The specific epithet refers to the gestalt of this ant, which resembles that of the flat wasps ( Chrysidoidea : Bethylidae ). While superficial, this resemblance was pronounced enough that the holotype and paratype of L. bethyloides were initially mis-sorted to Bethylidae incertae sedis at the Bishop Museum. The specific epithet is neuter.

Remarks.

Among the Leptanilla bethyloides species group, of which this is the only described species, L. bethyloides most closely resembles multiple undescribed morphospecies from southern Burma, differing in larger size (WL = 0.532-0.594 mm) and the proportions of the metasomal segments. Describing a new species of Leptanilla based solely upon male specimens, as here done for L. bethyloides , was eloquently argued against by Bolton (1990b), since it exacerbates the probable redundancy that plagues the taxonomy of Leptanilla . This description of L. bethyloides is justified only to give a formal species group name (i.e., the Leptanilla bethyloides species group) to a major clade of Leptanilla known only from male specimens.

The volsellae are known to be wholly lacking in Leptanilla zhg-mm03 ( Griebenow et al. in press), which shows very close morphological affinity to L. bethyloides ; therefore, I infer the absence of the volsellae in this species. The condition of the volsellae cannot be assessed in any other representatives of the Leptanilla bethyloides species group besides Leptanilla zhg-mm03. Given the relative lack of phylogenetic signal in the worker phenotype of Leptanilla and the scarcity of species in which the worker caste and phylogenetic position are both known, it is difficult to predict the morphology of the unknown worker of L. bethyloides or other members of the Leptanilla bethyloides species group, beyond a probable 1,1 palpal formula. It is conceivable that Leptanilla macauensis Leong, Yamane & Guénard, 2018 represents this worker, although unlikely, given the conformity of L. macauensis to the worker diagnosis for the Leptanilla revelierii species group, where it is placed in this study.

Figures

Figure 11. Leptanilla bethyloides, holotype (CASENT 0842864), male A profile view B dorsal view C full-face view. Scale bars: 0.1 mm (A, C); 0.5 mm (B).

Figure 12. Wings of Leptanilla bethyloides (CASENT 0842865), male. Scale bar: 0.2 mm.