Xymmer paniscus, Hamer & Gómez & Jocque, 2025

Hamer, Matthew T., Gómez, Kiko & Jocque, Merlijn, 2025, A new Xymmer Santschi, 1914 (Formicidae: Amblyoponinae) species from the Congo Basin, with male and female descriptions of X. muticus (Santschi, 1914), Zootaxa 5647 (5), pp. 479-495 : 489-493

Xymmer paniscus sp. nov. Hamer, Gómez & Jocque 2024

Zoobank: 4A98F88F-208D-452A-A335-4E77A21C724E

Figures 5A–C ; 6A–D

Material examined

Holotype DRC: [Tshuapa], Salonga National Park ; -1.7477 20.6803, 362 masl; 15.xii.2022; B. Pett Coll., Pitfall trap BINCO_DRC_22_0303_2. 1 worker on pin, DRC-PNS-132, RBINFOR1000800 [ RBINS]

Diagnosis

In full-face view, head distinctly longer than broad; lateral head margins subparallel. Anterior margin of the anteromedial clypeal lobe gradually convex. Mandible medially expanded; masticatory margin with seven teeth. Mesonotum delimited posteriorly by metanotal suture, wider than long, oval in shape. Mesopleuron not divided. In lateral view, peduncle short. In dorsal view, petiole narrow, distinctly longer than wide, lateral margins parallel.

Description

Measurements holotype (n = 1):

HW 0.30; HW₂ 0.28; HL 0.41; MBL 0.22; SL 0.24; WL 0.54; ML 0.54; PNW 0.18; HFL 0.23; PL 0.28; PH 0.18; DPW 0.13; DPL 0.42; AIIIW 0.24; AIVW 0.25; AIIIL 0.18; AIVL 0.20; AVL 0.07; AVIL 0.07; AVIIL 0.12; TL 2.12.

Indices: CI 73.43; MI 71.71; SI 79.28; WI 305.62; HFI 76.65; AIIII 130.22.

Head

In full-face view, head distinctly longer than broad, rectangular; lateral head margins subparallel, converging gradually along anterior two thirds, converging more strongly in posterior third; posterior corners gradually curved; occiput margin weakly concave. Mandible linear, half-length of head, widest medially; masticatory margin with seven teeth; from base to apex of mandible, first tooth minute, not easily discernible; second tooth small and triangular, third tooth larger than second and triangular, fourth and fifth teeth long with rounded apexes, sixth and seventh (apical) teeth long with a sharp apexes. Eye absent. Anterior clypeal margin with anteromedial clypeal lobe, projecting into inter-mandibular space, evenly convex. Antennal foramen partially visible anteriorly. Frontal carinae minute; scrobes absent. Genal teeth absent. Antennae with twelve segments; scape failing to reach posterior head margin by one third of head length; width of scape equal across whole length; pedicle longer than broad; flagellomeres incrassate; flagellomeres III to XI wider than long; antennal club absent; segment twelve longer than wide, terminating in a blunt point apically.

Mesosoma

In lateral view, dorsal mesosomal outline evenly convex; dorsoanteropronotal angle obtuse; propodeal dorsum gradually sloping towards declivity. In dorsal view, pronotum slightly wider than propodeum; mesosoma narrowest at mesonotum and anteriormost region of propodeum, gradually expanding outwards posterior at the propodeum. Pronotum anterior margin convex, posterior margin concave. Promesonotal articulation present. Metanotum wider than long, oval in shape. Metanotal groove present, one third width of the mesonotum; metanotal groove with a series of well-spaced longitudinal ribs. In lateral view, posterior margin of propodeum sinuate with a pair of posteriorly projecting lobes on its upper portion, concave on its lower portion. In dorsal view, propodeal declivital surface subtly concave. In lateral view, mesopleuron not divided. Anterolateral corner of the mesopleuron with a short blunt, anteriorly directed cuticular extension that fails to reach posteroventral corner of the pronotal side. Metapleural gland reservoir located anterolaterally on propodeum, reniform, occupying just less than half of lateral propodeal surface. Propodeal spiracle circular, located on mid height of propodeal side, distance between spiracle and gland reservoir less than spiracle diameter. Propodeal lobe inconspicuous, semi-circular. In lateral view, lower-upper mesopleural suture absent; meso-metapleural suture present only between the lower portion of these sclerites. Profemur broad, medially swollen, greater in size than subsequent femora of mid and hind legs. Metatibia roughly triangular, distinctly apically wider than at base, with pectinate comb and barbulate spur; mesotibia lacking spurs. Pretarsal claws simple, lacking teeth on the inner margin.

Metasoma

In lateral view, petiole with distinct peduncle; anterior face straight; dorsum subtly convex across length. Angle between anterior face and dorsum obtuse. Posteroventral angle obtuse, anteroventral margin of petiole shorter than posteroventral margin; anteroventral and posteroventral margin subtly concave. Petiole spiracle circular; located just posterodorsal to peduncle. In lateral view, peduncle short. In dorsal view, petiole narrow, distinctly longer than wide, lateral margins straight. In lateral view, anterolateral angle gradually curved, lacking posterior face, entirely fused to first gastral segment. In ventral view, petiolar poststernite ovoid; poststernite and laterotergite separated by narrow inverted U-shaped sulcus; ventrolateral junction distinctly marginated. In profile, ventral outline of first gastral sternite of abdominal segment III distinctly more convex than corresponding outline of the first gastral tergite. Girdling constriction of abdominal segment IV conspicuous. Sting present and well-developed.

Sculpture

Head dorsum and laterally densely foveolate; head dorsum with median, longitudinal smooth strip, extending from clypeal lobes and terminating just posterior of head margin; ventral surface with more scattered foveolae, interspaces smooth and shining. Mandible, scape and antennal segments smooth other than hair pits. Pronotal collar transversely strigulate. Pronotum, mesonotum and propodeum dorsum smooth, other than setae pits. Mesopleuron finely rugose; metapleuron ventrally with fine striations, otherwise smooth. Propodeal declivity smooth. Peduncle imbricate dorsally and laterally. Petiole, and gastral segments smooth other than setae pits. Visible portion of presternite III imbricate. Girdling constriction weakly areolate. Legs smooth, other than setae pits.

Pilosity

Mandible masticatory margin lined with a series of subdecumbent, stout setae directed into inter-mandibular region; mandible dorsum with subdecumbent setae. Scape with short, decumbent setae; flagellum with both short, decumbent, and erect, setae. Anterior clypeal margin with a pair of long curving setae that extend well into innermandibular space; a series of shorter setae also present. Head dorsum with numerous short, subdecumbent and appressed setae directed anteromedially; ventral and lateral surface also covered in numerous short, subdecumbent hairs. Frontal lobes with subdecumbent setae radiating outwards. Mesosomal dorsum and lateral surface of propodeum entirely with short, dense decumbent setae. Mesopleuron, lateral and declivity of propodeum mostly glabrous. Peduncle glabrous; petiole dorsum and lateral surface with short decumbent setae, and some suberect, longer setae. Posteroventral petiole angle numerous suberect setae. Gastral tergites and sternites with numerous, short subdecumbent setae as well as erect setae on the later gastral sternites. Pygidium and hypopygium with numerous long suberect setae, lacking spiniform setae. Legs covered in short, decumbent and appressed setae.

Colour

Head, mesosoma and metasoma brown orange; antenna and legs subtly lighter orange brown.

Recognition

Xymmer paniscus is morphologically distinct from both X. muticus and X. phungi by the convex anterior margin of the clypeal lobe, the distinctly longer than wide head, with subparallel lateral margins, and mandibles which are medially expanded. The masticatory margin is also lined with teeth of different shapes, most notably the long, apically rounded teeth which both X. muticus and X. phungi lack. The mesonotum in dorsal view is distinctly oval in X. paniscus , whereas in X. phungi it is semi-circular, and not distinctly delineated in X. muticus . The lateral margins of the petiole in dorsal view are straight in X. paniscus but convex in X. phungi and X. muticus . Finally, the overall size of X. paniscus is distinctly smaller than both species (e.g. head widths HW 0.303 <HW 0.506 -0.532).

Bionomics

Xymmer paniscus is highly likely to be a subterranean and/or leaf litter dwelling species owing to its small size, lack of eyes and protuberances across the body, as well as the light pigmentation which are all typical characteristics of subterranean and some leaf litter dwelling ants ( Wong & Guenard 2017). The individual described here was obtained through pitfall trapping which usually obtains epigeic ant species. Amblyoponinae are not unknown from pitfall traps, but are more typically collected via direct hand collection or leaf litter sifting with subsequent extraction ( Hamer et al., 2023). The specimen obtained here could have entered the trap after soil was disturbed following soil excavation necessary for the trap. Leaf litter extractions and further pitfall sampling conducted during the survey failed to obtain further specimens ( Jocque et al., 2023).

Remarks

Xymmer paniscus is the first record of the genus from the DRC. A single individual of X. paniscus was collected and subsequently described as new within this study. This is not atypical of Amblyoponinae , which are notoriously rarely collected, likely owing to their small colony sizes and general rarity. However, a single Xymmer specimen (X. afr01, CASENT0172228; ANIC; Figure 7 A-D) collected by J. Levieux from the Ivory Coast (approximately 3000 km from the type locality of X. paniscus ) morphologically resembles X. paniscus , so much so that we putatively suggest both are the same species. Both specimens have corresponding overall sizes, as well as mandible, clypeal lobe, metanotum and dorsal petiole shapes. Pubescence and sculpturing also seem to correspond, at least from inspection of specimen images. It was not possible to examine masticatory margin array, but examination of image both teeth shape and array superficially correspond. CASENT0172228 is damaged, lacking tibia, and tarsal segments across all legs. Unfortunately, this specimen was unobtainable at the time of this study, owing to the ANIC moving their facilities (Koopmans pers. comm.).

Etymology

Named for the endangered Bonobo apes ( Pan paniscus Schwarz, 1929 ) that inhabit the forest of the Democratic Republic of Congo.

Figures

FIGURE 5. Holotype of Xymmer paniscus (RBINFOR1000800). A) Lateral view, B) Dorsal view, C) Full face view.

FIGURE 6. Close up images of Xymmer paniscus (RBINFOR1000800). A) Mesosoma in dorsal view, B) Mandibles and lower head region in full-face view, C) Mesosoma in lateral view, D) Petiole in ventral view.

FIGURE 7. Xymmer afr1 (CASENT0172228, photographer April Noble). A) Lateral view, B) Full-face view, C) Dorsal view, D) Specimen labels. Images available from antweb.org.