Sphinctomyrmex Mayr, 1866b

Borowiec, Marek L., 2016, Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae), ZooKeys 608, pp. 1-280 : 170-174

Taxon classification Animalia Hymenoptera Formicidae

Sphinctomyrmex Mayr, 1866b

Type-species.

Sphinctomyrmex stali , by monotypy.

Sphinctomyrmex is a Neotropical lineage of extremely rarely encountered ants. Nothing is known about their biology.

Diagnosis.

Worker. Workers of Sphinctomyrmex are among the dorylines with prominent girdling constrictions between abdominal segments IV, V, and VI. These include Aenictogiton , Eusphinctus , Leptanilloides , and Zasphinctus . Sphinctomyrmex can be differentiated from these genera by a combination of presence of propodeal lobes and propodeal spiracle positioned high (no lobes and spiracle low on propodeum in Aenictogiton ), metapleural gland trench narrow (broad in Zasphinctus ), large pygidium armed with modified setae (pygidium unarmed and reduced to a narrow strip in Leptanilloides ), and girdling constriction between abdominal segments III and IV cross-ribbed and segment IV similar in size to segments V and VI (girdling constriction smooth and segment IV larger than V and VI in Eusphinctus ). Among these genera, only Leptanilloides occurs in sympatry with Sphinctomyrmex .

Male. The males of Sphinctomyrmex also show girdling constrictions between abdominal segments III, IV, and V. Among male dorylines, this state is restricted to the Old World taxa Eusphinctus and Zasphinctus . They differ in wing venation, shape of abdominal sternite IX and genitalia and the venation characters are the easiest to assess for identification. The marginal cell is closed in Sphinctomyrmex (open in Eusphinctus ) and the costal vein (C) is present in the fore wing (absent in Zasphinctus ). Malagasy Tanipone may also have weak abdominal constrictions but are distinguished by very long, 6-segmented maxillary palps that are visible in mounted specimens and reach occipital foramen. Some Acanthostichus or Cylindromyrmex males may also have gastral constrictions but in the former helcium is broad and supraaxial and in the latter there are two spurs on hind tibiae.

Description.

Worker.Head: Antennae with 12 segments. Apical antennal segment conspicuously enlarged, much broader than and longer than two preceding segments combined. Clypeus with cuticular apron. Lateroclypeal teeth absent. Parafrontal ridges reduced. Torulo-posttorular complex vertical. Antennal scrobes absent. Labrum with median notch or concavity. Proximal face of stipes projecting beyond inner margin of sclerite, concealing prementum when mouthparts fully closed. Maxillary palps 3-segmented. Labial palps 3-segmented. Mandibles triangular, edentate. Eyes present, composed of 1-5 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. Promesonotal connection with Pronotomesopleural suture completely fused or with Pronotomesopleural suture present, weakly differentiated, immobile. Pronotomesopleural suture completely fused but impressed line present. Mesometapleural groove weakly impressed. Transverse groove dividing mesopleuron 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 with bulla visible through cuticle. Propodeal lobes present, well developed. Metasoma: Petiole anterodorsally immarginate, dorsolaterally immarginate, and laterally above spiracle marginate. Helcium in relation to tergosternal Pronotomesopleural suture placed at posttergite and axial. 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 gutter-like and cross-ribbed. 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. Hypopygium unarmed. 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. Metabasitarsal gland absent. Hind pretarsal claws simple. Polymorphism: Monomorphic.

Male.Head: Antennae with 13 segments. Clypeus with cuticular apron. Parafrontal ridges absent. Torulo-posttorular complex vertical. Maxillary palps unknown. Labial palps unknown. Mandibles triangular, edentate. Ventrolateral margins of head without lamella or ridge extending towards mandibles and beyond carina surrounding occipital foramen. Carina surrounding occipital foramen ventrally absent. Mesosoma: Pronotal flange not separated from collar by distinct ridge. Notauli present. Transverse groove dividing mesopleuron present. Propodeal declivity with dorsal edge present, incomplete. Metapleural gland opening present. Propodeal lobes present. Metasoma: Petiole anterodorsally immarginate, dorsolaterally immarginate, and laterally above spiracle immarginate. Helcium in relation to tergosternal Pronotomesopleural suture placed at posttergite and axial. Prora forming a U-shaped margin with median ridge. 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 and cross-ribbed. 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, with lateral apodemes about as long as medial apodeme, directed anteriorly (towards head). Genitalia: Cupula long relative to rest of genital capsule and shorter ventrally than dorsally. Basimere broadly fused to telomere, with no sulcus trace at junction, 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 absent. Metabasitarsal glands absent. Hind pretarsal claws simple. Wings: Tegula present, broad, demiovate in shape. Vein C in fore wing present. Pterostigma broad. Abscissa R·f3 present, running toward distal wing margin and enclosing cell with Rs·f5. Abscissae Rs·f2-3 absent or present, very short and disconnected from Rs+M. Cross-vein 2r-rs present, forming base of 2r-rs&Rs·f4-5 in absence of 2rs-m or differentiated from Rs·f4 by presence of short Rs·f2-3. Abscissae Rs·f4-5 present, fused in absence of 2rs-m. Abscissa M·f2 in fore wing contiguous with Rs+M. 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. 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 present, extending past Sc+R but not reaching distal wing margin. Vein Sc+R in hind wing present. Abscissa Rs·f1 in hind wing pre sent, longer than 1rs-m. Abscissa Rs·f2 in hind wing present, short, not reaching wing margin. Cross-vein 1rs-m in hind wing absent. Vein M+Cu in hind wing present. Abscissa M·f1 in hind wing absent. Abscissa M·f2 in hind wing absent. Cross-vein cu-a in hind wing absent or stub present. Vein Cu in hind wing present. Vein A in hind wing with abscissa A·f1 present.

Gyne. Gynes are so far only known for Sphinctomyrmex stali . One apparently dealated gyne has been collected in this species, in addition to ergatoid/intercaste specimens with relatively large eyes and ocelli. For a detailed discussion see Feitosa et al. (2011).

Larva. Not described. Cocoons unknown.

Distribution.

So far only known from Amazonas, Santa Catarina, and São Paulo states in Brazil, and Jujuy province in Argentina but likely present throughout most of South America.

Taxonomy and phylogeny.

For taxonomic history see under Eusphinctus .

The three known species of Sphinctomyrmex are reviewed and keyed in Feitosa et al. (2011).

The affinities of the genus are not known exactly but genomic data suggests that it forms a clade with Leptanilloides and the Eciton genus-group (Borowiec, in prep.).

Biology.

Virtually nothing is known of this lineage’s biology, and no nest series have ever been collected ( Feitosa et al. 2011). Several workers have been collected by digging in soil in a dry forest habitat in Jujuy, Argentina (Brian Fisher pers. comm.).

Species of Sphinctomyrmex

Sphinctomyrmex marcoyi Feitosa, Brandão, Fernández and Delabie, 2011: Brazil

Sphinctomyrmex schoerederi Feitosa, Brandão, Fernández and Delabie, 2011: Brazil

Sphinctomyrmex stali Mayr, 1866b: Brazil