Two new species of Ooceraea (Hymenoptera, Formicidae, Dorylinae) from India with ten-segmented antennae

Abstract Two new species, O. decamerasp. nov. and O. joshiisp. nov., of the ant genus Ooceraea are described from India. These species differ from other known congeners on the basis of number of antennal segments. An illustrated key to the known species based on the worker caste is also provided.


Introduction
The taxonomic history of the ant genus Ooceraea Roger, 1862 has been challenging, since its inception based on the type species O. fragosa. The taxonomic ambiguity has led to its uncertain placements in different subfamilies: in Myrmicinae (Mayr 1865;Emery 1877), in Ponerinae (Dalla Torre 1893; Forel 1893) and in Dorylinae (Emery 1895). Ooceraea was treated as a subgenus of Cerapachys (Emery 1902;Wheeler W.M. 1902;Emery 1911), and as a junior synonym of Cerapachys (Brown 1975). This dilemma has lately been resolved with a comprehensive revision of generic-level classification of the subfamily Dorylinae. Ooceraea was resurrected as a valid genus in Dorylinae with a distinctive combination of characters, by which it can be distin-guished from other Dorylinae genera. These include: propodeal spiracle positioned low on the sclerite; pygidium armed with modified setae; antennae with 11 or fewer segments; pronotomesopleural suture developed; abdominal segment III strongly tubulated (forming "postpetiole") and no constrictions between abdominal segments IV, V and VI. Ooceraea can be distinguished from the closely allied Syscia Roger, 1861 on the basis of abdominal segment III relatively narrow in dorsal view and similar in size to the preceding abdominal segment II (petiole); in lateral view, abdominal tergite IV not folding over sternite and the anterior portion of the sternite visible; hind basitarsi not dilating distally, circular in cross-section and metabasitarsal glands absent (Borowiec 2016).
The genus is currently represented by 14 species (Bolton 2020). Six of these are reported from the Australian and Oceanian regions, five from the Oriental region and two species from the Palearctic region (Holt et al. 2013;Janicki et al. 2016;Guénard et al. 2017;Yamada et al. 2018;Zhou et al. 2020); while the 14 th species O. biroi (Forel, 1907) is probably native to the Asian continent, and has been introduced to Southeast Asia, the Pacific islands, Madagascar and the Caribbean islands (Borowiec 2016;Janicki et al. 2016;Guénard et al. 2017) (Fig. 10). The antennal count has been found to be one of the significant species-level diagnostic characters in the genus. Eight of the known Ooceraea species possess nine-segmented antennae, while five possess elevensegmented antennae and one species has recently been reported with eight-segmented antennae (Zhou et al. 2020). In India, the genus is represented by two species viz. Ooceraea alii (Bharti & Akbar, 2013) and Ooceraea besucheti (Brown, 1975) with nineand eleven-segmented antennae respectively (Bharti et al. 2016). Here in, we describe two new species with ten-segmented antennae from India, thus adding to the known diversity of this considered rare genus. A key to the known species based on the worker caste is also provided.

Materials and methods
Taxonomic analysis was conducted on a Nikon SMZ 1500 stereo zoom microscope with maximum mag nification of 112.5×. Digital images of the specimens were prepared using a Nikon SMZ 1500 stereomicroscope fitted with a Micro Publisher digital camera (Figs 1-4) and Leica MZ 16 stereomicroscope with a JVC digital video camera (Figs 5-9). All the images were cleaned with Adobe Photoshop CS5 and Helicon Filter 5. Morphological measurements were recorded in millimeters on a Nikon SMZ 1500 stereomicroscope. Morphological terminology and standard measurements follow Borowiec (2016) and Yamada et al. (2018).

HL
Head  Worker description. Head in full-face view, almost as long as broad, with lateral margin weakly convex and converging anteriorly, with posterior margin concave medially and posterior lateral corners rounded. Anterior clypeal margin reduced and slightly concave in the middle. Eyes present, small in size, with two ommatidia, parafrontal ridge prominently produced. Mandibles edentate, sub-triangular. Antenna 10-segmented; scape short and clavate, reaching almost mid-length of the head; apical funicular segment fusiform. Frontal lobes reduced. Antennal sockets fully exposed from above.
Mesosoma in lateral view weakly convex; promesonotal suture and metanotal groove absent. Pronotum in dorsal view anteriorly marginate. Propodeum in dorsal view with posterior margin concave; propodeal declivity in lateral view slightly concave, with lateral margin slightly marginate; propodeal lobe reduced. Petiolar node in dorsal view as long as broad, rounded anteriorly, in lateral view hemiglobular; subpetiolar process well-developed, with sickle-shaped anteroventral apex. Postpetiole in dorsal view subtrapezoidal, with anterior margin transverse and posterior margin convex, in lateral view with anteroventral corner angulate. Gastral segment I (abdominal segment IV) large, occupying the most part of gaster, in lateral view with dorsal margin weakly and roundly convex.
Pilosity and Pubescence. Body covered with erect or sub-erect hairs; sides of head and legs covered with shorter hairs; scape and funicular segments covered with short decumbent or subdecumbent hairs.
Body coloration. Head and gaster light brown; mesosoma, petiole and postpetiole darker than the head; legs yellowish brown.

Male. Unknown.
Recognition. Ooceraea joshii sp. nov. and O. decamera sp. nov. (described below) are distinctly separated from the other valid congeners by having 10-segmented antennae. Furthermore, the two new species are well distinguished from each other by a combination of the following characters: head shape (almost as long as broad in O. joshii sp. nov., rectangular, distinctly longer than broad in O. decamera sp. nov.); presence of ommatidia (present in O. joshii sp. nov. and absent in O. decamera sp. nov.); propodeal lobes (reduced versus roundly produced); petiolar node in lateral view (hemiglobular versus rectangular); subpetiolar process (anteroventral part sickle-shaped versus forming a rectangular and semitransparent lobe); pilosity (head and body comparatively more pilose in O. joshii sp. nov.); and sculpturation (head, mesosoma, petiolar, postpetiolar node, and gaster with more pronounced foveolate sculpture in O. joshii sp. nov.).
Bionomics. The type series was found in leaf litter samples collected from the Medaganam region of the Periyar Tiger Reserve situated at an elevation of 780 meters. The region is composed of an undisturbed tropical moist evergreen forest with low light penetration, with a mean average daytime temperature of 30 °C.     Worker description. Head in full-face view rectangular, distinctly longer than broad (CI 74), with lateral sides weakly convex, with posterior margin concave medially, with occipital lobes/corners angulate. Anterior clypeal margin slightly projecting forward. Eyes absent. Parafrontal ridge prominent and elevated. Mandibles edentate but weakly serrate. Antennae with 10 segments; scape short, clavate, slightly surpassing the mid-length of head. Frontal lobes reduced. Antennal sockets fully exposed from above.
Mesosoma in lateral view almost flat; promesonotal suture and metanotal groove absent. Pronotum in dorsal view with anterior margin weakly and roundly convex, with humeral corner rounded. Propodeum in dorsal view with posterior margin concave; propodeal declivity in lateral view almost straight, with lateral margin marginate; propodeal lobe roundly produced. Petiolar node in dorsal view subtrapezoidal, distinctly broader than long, in lateral view rectangular with anterior and posterior margins almost straight and dorsal margin weakly convex. Subpetiolar process well-developed, with anteroventral part forming a rectangular and semitransparent lobe. Postpetiole broader than long, anterior margin weakly concave and posterior margin weakly convex, in lateral view with anteroventral part broadly and roundly produced. Gastral segment I (abdominal segment IV) large occupying the most part of gaster, in lateral view with dorsal margin almost straight, base of cinctus of first gastral tergite cross-ribbed.
Pilosity and pubescence. Whole body covered with pale yellow erect and sub-erect hairs; appressed pubescence abundant on antennae and legs.

Bionomics. Unknown.
Distribution. Known only from the type locality. The place has been transformed into agricultural land and is prone to anthropogenic activities. Thus, this reinforces the concept that important biodiversity components, which are already rare, are imperiled due to local extinctions.
Etymology. The species epithet decamera refers to the ten-segmented antennal count.  Anterolateral shoulders of the first gastric segment as seen from above broadly rounded and gradually widening caudad (Fig. A)  Anterolateral shoulders of the first gastric segment abruptly rounded, accentuating the medium concavity that receives the postpetiole (Fig. B)  Lateral ridge of posterior face of propodeum armed with two pairs of denticles (Vietnam) (Fig. A)  Lateral ridge of posterior face of propodeum without denticles (Fig. B) ......7 7 Spaces between foveolae shagreen-like, giving the integument a rough appearance (Fig. A)  Species small in size (HW< 40 mm); posterior margin of head distinctly concave in the middle (Fig. B)  Sides of propodeum and sides of petiole with dense, deeply impressed foveae that are discernibly wider in diameter than propodeal spiracle or foveae on head. Dark species (Fiji) (Fig. A)  Head as long as broad; eyes present; propodeal lobes reduced; petiolar node in lateral view hemiglobular; anteroventral part of subpetiolar process sickleshaped; head and body comparatively more pilose (India) (Fig. A, B)  Head distinctly longer than broad; eyes absent; propodeal lobes roundly produced; petiole node in lateral view rectangular; anteroventral part of subpetiolar process forming a rectangular and semitransparent lobe (India) (Fig. C, D)  14 Anterior portion of pronotum with distinct ridge; petiole and postpetiole in dorsal view broader than long (Sri Lanka) (Fig. A) (Zhou, 2006) is not available, so this species has been not included in the key. However, as cited in the comparative diagnosis, O. guizhouensis is close to O. besucheti and O. fragosa, but differs in having coarse pilose punctures on the surface of the mandibles, petiolar node distinctly longer than broad and is without eyes.