Zasphinctus

Zasphinctus is a moderately speciose lineage of specialized ant predators, most prominent in Australia.

Identification
Borowiec (2016) - Worker The workers of Zasphinctus are ants of variable size, color, and sculpturation, but always possessing conspicuous girdling constrictions between abdominal segments IV, V, and VI. The eyes absent in most species. Zasphinctus can be distinguished from other lineages with pronounced abdominal constrictions by highly-positioned propodeal spiracles, propodeal lobes present, pygidium large and armed with modified setae, and pronotomesopleural suture fused. See also diagnoses of Eusphinctus and Sphinctomyrmex.

Male The males of Zasphinctus also possess the characteristic abdominal constrictions between abdominal segments IV, V, and VI and can be recognized by a combination of costal vein (C) absent from the fore wing, submarginal cell (SMC) closed by Rs·f2-f3, vein 2rs-m absent, pronotum not marginate anterodorsally, and antennae 13-segmented. This venation is similar to Lividopone and Parasyscia but Zasphinctus can be recognized by the presence of abdominal constrictions and different appearance of abdominal sternite IX (subgenital plate). In Zasphinctus, the sternite is abruptly constricted proximal to where spines arise and is much wider at midlength. In Lividopone and Parasyscia in contrast, the sternite IX is usually gradually narrowing to the point of bifurcation. The males of Eusphinctus and Sphinctomyrmex have similar abdominal constrictions but the former has 12-segmented antennae and the latter has different wing venation with costal vein present.

Brown (1975) gave a preliminary key to Indomalayan and Australasian species.

Distribution
Borowiec (2016) - Distributed throughout Australasia, including New Caledonia and New Guinea, and the Afrotropics. Most species are known from Australia, with only three taxa described from Africa. Recently a species has been described from Thailand (Jaitrong et al. 2016), and unidentified Zasphinctus males are also known from Myanmar (author’s unpublished observations).

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Biology
Wilson provided notes on the biology of Zasphinctus caledonicus from New Caledonia and Z. steinheili from Australia. The former was observed raiding a nest of Stigmacros ants in the field, and the latter was feeding on ant brood of several species in the laboratory. Both were reported to have colonies containing multiple ergatoid gynes and synchronized brood. Buschinger et al. (1990) studied a species related to Z. steinheili in more detail under laboratory conditions. They largely confirmed Wilson’s preliminary observations and further demonstrated functional polygyny, since most dissected queens were fertilized with well-developed ovaries. The ants would indeed take brood of several ant species, including European forms, but the colonies ceased producing new eggs after two brood cycles were completed and thereafter slowly declined. Briese (1984) described a nest evacuation response in a Monomorium species raided by Zasphinctus in Australia. Hölldobler et al. (1996) described the metatibial gland of Z. steinheili.

Nomenclature

 *  ZASPHINCTUS  [Dorylinae]
 * Zasphinctus Wheeler, W.M. 1918a: 219 [as subgenus of Eusphinctus]. Type-species: Sphinctomyrmex turneri, by monotypy.
 * Zasphinctus junior synonym of Sphinctomyrmex: Brown, 1975: 31.
 * Zasphinctus as genus: Borowiec, 2016: 237.

Borowiec (2016) - This name is here revived from synonymy with Sphinctomyrmex. For a brief account of taxonomic history and justification see under Eusphinctus. The position of Zasphinctus within dorylines appears to be well established as the sister group to Parasyscia, and it is reasonably certain that this lineage was derived independently from the Neotropical Sphinctomyrmex (Figure 1; Brady et al. 2014, Borowiec, in prep.).

Worker
Borowiec (2016) - Head: Antennae with 11 or 12 segments. Apical antennal segment conspicuously enlarged, much broader than and longer than two preceding segments combined. Clypeus with cuticular apron. Lateroclypeal teeth absent or present. Parafrontal ridges absent or reduced. Torulo-posttorular complex vertical. Antennal scrobes absent. Labrum with median notch or concavity. Proximal face of stipes not projecting beyond inner margin of sclerite, prementum exposed when mouthparts fully closed. Maxillary palps 3-segmented. Labial palps 3-segmented. Mandibles triangular, with teeth or edentate. Eyes absent or present, composed of more than 20 ommatidia. Ocelli absent. Head capsule with differentiated vertical posterior surface above occipital foramen. Ventrolateral margins of head without lamella or ridge extending towards mandibles and beyond carina surrounding occipital foramen. Posterior head corners dorsolaterally immarginate. Carina surrounding occipital foramen ventrally present. Mesosoma: Pronotal flange separated from collar by distinct ridge or not. Promesonotal connection with suture completely fused. Pronotomesopleural suture completely fused. Mesometapleural groove not impressed or weakly impressed. Transverse groove dividing mesopleuron absent or present. Pleural endophragmal pit concavity present. Mesosoma dorsolaterally immarginate. Metanotal depression or groove on mesosoma absent. Propodeal spiracle situated low on sclerite. Propodeal declivity with distinct dorsal edge or margin and rectangular in posterior view. Metapleural gland without bulla visible through cuticle. Propodeal lobes present, well developed. Metasoma: Petiole anterodorsally marginate or immarginate, dorsolaterally immarginate, and laterally above spiracle marginate or rarely immarginate. Helcium in relation to tergosternal suture placed at posttergite and helcium axial, occasionally slightly supraaxial. Prora simple, not delimited by carina. Prora forming a U-shaped margin with median ridge. Spiracle openings of abdominal segments IV–VI circular. Abdominal segment III anterodorsally immarginate and dorsolaterally immarginate. Abdominal segment III more than half size of succeeding segment IV, which is weakly constricted at presegmental portion (uninodal waist). Girdling constriction of segment IV present, i.e. pre- and postsclerites distinct. Cinctus of abdominal segment IV not impressed. Abdominal segment IV not conspicuously largest segment. Abdominal tergite IV not folding over sternite, and anterior portions of sternite and tergite equally well visible in lateral view. Girdling constriction between pre- and posttergites of abdominal segments V and VI present. Girdling constriction between pre- and poststernites of abdominal segments V and VI present. Pygidium large, with impressed medial field, and armed with modified setae, sometimes notched. Hypopygium armed with modified setae. Legs: Mid tibia with single pectinate spur. Hind tibia with single pectinate spur. Hind basitarsus not widening distally, circular in cross-section. Posterior flange of hind coxa not produced as raised lamella. Metatibial gland absent or an oval patch of whitish cuticle. Metabasitarsal gland absent. Hind pretarsal claws simple. Polymorphism: Monomorphic.

Queen
Borowiec (2016) - Alate, ergatoid, or subdichthadiigyne. Alate gynes are known in an undescribed species from Africa (Brown 1975) and in Zasphinctus occidentalis (Clark 1924a). In Zasphinctus asper, Zasphinctus duchaussoyi, and Zasphinctus steinheili known gyne specimens are wingless ergatoids that possess eyes and ocelli. The gyne of Zasphinctus imbecilis can be considered a ‘subdichthadiigyne’; it possesses only vestigial eyes and one or no ocelli in addition to enlarged gaster. Descriptions and extensive discussions of gyne morphology in Zasphinctus can be found in Brown (1975), Clark (1924a), and Wheeler (1918).

Male
Borowiec (2016) - Head: Antennae with 12 or 13 segments. Clypeus with cuticular apron. Parafrontal ridges absent. Torulo-posttorular complex vertical. Maxillary palps 3-segmented. Labial palps 3-segmented. Mandibles triangular, edentate to falcate. Ventrolateral margins of head without lamella or ridge extending towards mandibles and beyond carina surrounding occipital foramen. Carina surrounding occipital foramen ventrally present. Mesosoma: Pronotal flange separated from collar by distinct ridge. Notauli present or, more rarely, absent. Transverse groove dividing mesopleuron present. Propodeal declivity with distinct dorsal edge or margin. Metapleural gland opening absent. Propodeal lobes present. Metasoma: Petiole anterodorsally marginate, dorsolaterally immarginate, and laterally above spiracle marginate. Helcium in relation to tergosternal suture placed at suture and axial. Prora forming a V-shaped protrusion. Spiracle openings of abdominal segments IV–VI circular. Abdominal segment III more than half size of succeeding segment IV; latter weakly constricted at presegmental portion (uninodal waist). Girdling constriction of segment IV present, i.e. pre- and postsclerites distinct. Cinctus of abdominal segment IV gutter-like, not sculptured. Girdling constriction between pre- and postsclerites of abdominal segments V and VI present. Abdominal segment IV not conspicuously largest segment. Abdominal sternite VII simple. Abdominal sternite IX distally armed with two spines curved dorsally at apices, with lateral apodemes shorter than or about as long as medial apodeme, directed anteriorly (towards head); all apodemes long. Genitalia: Cupula long relative to rest of genital capsule and shorter ventrally than dorsally. Basimere broadly fused to telomere, with sulcus discernable at junction, and ventrally with left and right arms abutting. Telomere gradually tapering toward apex. Volsella laterally flattened, at apex with dorsal lobe and hooked ventrally. Penisvalva laterally compressed, rounded at apex. Legs: Mid tibia with single pectinate spur. Hind tibia with single pectinate spur. Posterior flange of hind coxa not produced as raised lamella. Metatibial gland present as oval patch of whitish cuticle. Metabasitarsal glands absent. Hind pretarsal claws simple. Wings: Tegula present, broad, demiovate in shape. Vein C in fore wing absent. Pterostigma broad. Abscissa R·f3 absent. Abscissae Rs·f2–3 present, connecting with Rs+M&M·f2 or disconnected from Rs+M. Cross-vein 2r-rs present, differentiated from Rs·f4 by presence of Rs·f2–3. Abscissae Rs·f4–5 present, fused in absence of 2rs-m. Abscissa M·f2 in fore wing present, separated from Rs+M by Rs·f2. Abscissa M·f4 in fore wing present, not reaching wing margin. Cross-vein 1m-cu in fore wing present. Cross-vein cu-a in fore wing present, arising from M+Cu and proximal to M·f1 or near M·f1. Vein Cu in fore wing present, with only Cu1 branch prominent. Vein A in fore wing with abscissae A·f1 and A·f2 present. Vein C in hind wing absent. Vein R in hind wing absent. Vein Sc+R in hind wing absent. Abscissa Rs·f1 in hind wing not differentiated in absence of Sc+R. Abscissa Rs·f2 in hind wing present, not reaching wing margin. Cross-vein 1rs-m in hind wing fused with M·f1. Vein M+Cu in hind wing present. Abscissa M·f1 in hind wing present. Abscissa M·f2 in hind wing absent. Cross-vein cu-a in hind wing present. Vein Cu in hind wing present. Vein A in hind wing with abscissae A·f1 and A·f2 present; The latter a stub.

Larva
Cocoons present.