Syscia

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Syscia is the only doryline genus with a disjunct distribution between the Old and New World. Members of this genus are usually found in leaf litter, rotting wood and soil cores, and are thus considered part of the cryptobiotic fauna (Borowiec 2016; Jaitrong et al. 2020; Longino & Branstetter 2021). Previously, only five species had been described worldwide (Borowiec 2016). Therefore, as Borowiec (2016) pointed out at the time, there might be more morphospecies presented in collections from the Old World and additional undescribed species in the New World. Since then, Jaitrong et al. (2020) described two new species from Thailand and Aswaj et al. (2021) described and illustrated one new species from India. Longino and Branstetter (2021) integrated ultra-conserved element (UCE) phylogenomics with traditional taxonomy to reveal and name 31 new species of Syscia in Central and South America, resulting in an increase in the number of known species of Syscia in the New World from 3 to 34. By contrast, the known species of Syscia in the Old World are still few, with only 5 recorded (Antweb 2022). Except for Syscia typhla, which is widespread, the remaining species of Syscia are generally native to their type-localities or surrounding country, e.g., Syscia chaladthanyakiji and Syscia reticularis in Thailand, Syscia humicola in Korea and Japan, and Syscia indica in India. The type-locality of Syscia typhla is Sri Lanka, and this species also was recorded in northern India (Ghosh et al. 2007), southern China (Xu 1998; Xu et al. 1999; Gu et al. 2019), and Japan (Sonobe 1973; Abe 1974). However, a detailed examination of relevant specimens of Xu (1998) and Xu et al. (1999), revealed that the specimens of Ooceraea biroi were misidentified as S. typhla. And the species Syscia zhoui was misidentified as S. typhla by Gu et al. (2019). Therefore, there is currently no distribution of the Syscia in the ant fauna of China. Given the complexity and heterogeneity of the geography and climate in China, there are likely to be additional cryptic and undescribed species of Syscia to be discovered there. (Du et al., 2024)

Identification

Borowiec (2016) - Worker. Syscia workers have 11- or 9-segmented antennae, eyes small to absent, and are usually heavily sculptured with abundant body pilosity. Body is usually uniformly colored and ranges from yellow through reddish to dark brown but never black. They possess apparently autapomorphic characters that serve to easily distinguish this lineage from all other dorylines: basal segment of hind tarsus widening distally with a light patch of cuticle on the inner (flexor) side, and abdominal tergite IV anteriorly folding over sternite. This combination is unique to Syscia and although species in other lineages may have similar habitus (Ooceraea, Parasyscia), none of these possess these characteristics.

Male. The males of Syscia have the number of antennal segments reduced to 12. They can be difficult to distinguish from Ooceraea (see under diagnosis for that genus), but a lack of constrictions between abdominal segments IV, V, and VI, presence of a spur on middle tibia, and no costal vein (C) in the fore wing will distinguish them from the other genera where a reduction in the number of antennal segments is currently known, which include Acanthostichus, Eusphinctus, and Simopone.

Keys including this Genus

 

Keys to Species in this Genus

Distribution

Borowiec (2016) - This is the only doryline genus with a disjunct distribution between the New and Old Worlds (except for tramp Ooceraea biroi), with one center of diversity in Central America, with records from the Antilles (Cuba and Dominican Republic) and as far north as Arkansas, United States, and the other center in Southeast Asia west of Wallace’s Line, especially Borneo, reaching Japan to the north and southern India to the west.

Distribution and Richness based on AntMaps

Species by Region

Number of species within biogeographic regions, along with the total number of species for each region.

Afrotropical Region Australasian Region Indo-Australian Region Malagasy Region Nearctic Region Neotropical Region Oriental Region Palaearctic Region
Species 0 0 0 0 3 33 4 2
Total Species 2841 1736 3045 932 835 4379 1741 2862

Biology

Borowiec (2016) - Syscia species are found in leaf litter samples and soil cores. The foraging habits are not known. Syscia augustae, a species present in southern United States, has been observed on diurnal emigrations and briefly studied under laboratory conditions (Clint Penick pers. comm.). The brood production in S. augustae is synchronized. Gyne morphology varies in this lineage, with ergatoid, brachypterous, and fully winged individuals known. There is an observation of a brachypterous gyne aggregation under a stone (Michael Branstetter pers. comm.). It is unknown whether this represents cooperative colony foundation.

Flight Period

All Flight Records for Genus

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Taxon Month Source Notes
Syscia augustae Jun Jul Aug antkeeping.info

Life History Traits

  • Compound colony type: not parasitic (Greer et al., 2021)
  • Nest site: hypogaeic (Greer et al., 2021)

Castes

Morphology

Worker Morphology

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 • Eyes: 0-10 ommatidia • Caste: none or weak • Sting: absent • Metaplural Gland: present • Cocoon: absent

Phylogeny

Dorylinae

Lioponera (76 species, 0 fossil species)

Lividopone (1 species, 0 fossil species)

Parasyscia (57 species, 0 fossil species)

Zasphinctus (24 species, 0 fossil species)

Vicinopone (1 species, 0 fossil species)

Simopone (40 species, 0 fossil species)

Tanipone (10 species, 0 fossil species)

Eusphinctus (2 species, 0 fossil species)

Ooceraea (17 species, 0 fossil species)

Syscia (41 species, 0 fossil species)

Eburopone (2 species, 0 fossil species)

Aenictus (226 species, 0 fossil species)

Aenictogiton (7 species, 0 fossil species)

Dorylus (127 species, 0 fossil species)

Cerapachys (5 species, 0 fossil species)

Chrysapace (4 species, 0 fossil species)

Yunodorylus (4 species, 0 fossil species)

Neocerapachys (2 species, 0 fossil species)

Acanthostichus (23 species, 1 fossil species)

Cylindromyrmex (10 species, 3 fossil species)

Sphinctomyrmex (3 species, 0 fossil species)

Leptanilloides (19 species, 0 fossil species)

Neivamyrmex (129 species, 1 fossil species)

Cheliomyrmex (4 species, 0 fossil species)

Labidus (9 species, 0 fossil species)

Eciton (29 species, 0 fossil species)

Nomamyrmex (2 species, 0 fossil species)

See Phylogeny of Dorylinae for details.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • SYSCIA [Dorylinae]
    • Syscia Roger, 1861a: 19. Type-species: Syscia typhla, by monotypy.
    • Syscia subgenus of Cerapachys: Wheeler, W.M. 1902d: 185; Emery, 1902c: 24.
    • Syscia senior synonym of Cysias: Emery, 1911d: 10.
    • Syscia junior synonym of Cerapachys: Kempf, 1972a: 76.
    • Syscia as genus: Borowiec, 2016: 219.

Taxonomic Notes

Du et al. (2024) - The genus Syscia was first proposed by Roger (1861) in a paper on ‘Ponera-like ants’ based on the type species Syscia typhla, and was regarded as a member of the tribe “Cerapachysii”. Since then, the taxonomic status of this genus has changed many times by different myrmecologists, e.g., considered as a valid genus (Forel 1900; Dalla Torre 1903; Bingham 1903), as a subgenus of Cerapachys (Wheeler 1902, 1910, 1922; Emery 1902, 1911; Forel 1917; Donisthorpe 1943) or a junior synonym of Cerapachys (Kempf 1972; Brown 1975). More recently, Brady et al. (2014) found Cerapachys to be non-monophyletic. Additionally, according to phylogenetic inference based on molecular data for the major dorylomorph lineages, they found that Neotropical and Indomalayan species of Syscia together formed a clade distinct from other genera. Later, Borowiec (2016) systematically revised the generic classification of the subfamily Dorylinae Leach, 1815 based on molecular phylogenetic evidence and a critical reappraisal of doryline morphology. The result of their analysis divided the former Cerapachys into 9 different monophyletic genera and recognized Syscia as a valid genus again. Meanwhile, they comprehensively described the specific characteristics of different types of Syscia, and diagnosed their unique autapomorphic characteristics: basal segment of hind tarsus widening distally with a light patch of cuticle on the inner (flexor) side, and abdominal tergite IV anteriorly folding over sternite. That outstanding work provided a solid foundation for the subsequent classification of the genus Syscia.

Description

Worker

Borowiec (2016) - Head: Antennae with 9 or 11 segments. Apical antennal segment conspicuously enlarged, much broader than and longer than two preceding segments combined. Clypeus with cuticular apron. Lateroclypeal teeth present. 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 2-segmented. Labial palps 2-segmented. Mandibles triangular, edentate. Eyes absent or 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 not separated from collar by distinct ridge. Promesonotal connection with suture completely fused. Pronotomesopleural suture visible, unfused up to notal surface. Mesometapleural groove not impressed. Mesometapleural groove weakly impressed. Transverse groove dividing mesopleuron present or absent. Pleural endophragmal pit concavity present. Mesosoma dorsolaterally immarginate. Metanotal depression or groove on mesosoma absent. Propodeal spiracle situated low on sclerite. Propodeal declivity without 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 immarginate. Helcium in relation to tergosternal 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, not sculptured or cross-ribbed. Abdominal segment IV not conspicuously largest segment or conspicuously largest segment. Abdominal tergite IV folding over sternite, anterior portion of sternite concealing tergite in lateral view. Girdling constriction between pre- and posttergites of abdominal segments V and VI absent. Girdling constriction between pre- and poststernites of abdominal segments V and VI absent. Pygidium medium-sized, with impressed medial field, and armed with modified setae. Hypopygium unarmed or armed with modified setae. Legs: Mid tibia with single pectinate spur. Hind tibia with single pectinate spur. Hind basitarsus widening distally, oval in cross-section. Posterior flange of hind coxa not produced as raised lamella. Metatibial gland present as oval patch of whitish cuticle. Metabasitarsal gland present. Hind pretarsal claws simple. Polymorphism: Monomorphic.

Queen

Borowiec (2016) - Alate, brachypterous, or ergatoid with eyes of variable size and with or without ocelli. Gynes are known for S. augustae, Syscia honduriana, Syscia humicola, and Syscia typhla. In S. typhla the gynes have well-developed flight sclerites on the mesosoma but I have never examined a specimen with wings. Field observations of S. augustae or a closely related species suggest that virgin queens may be brachypterous (Michael Branstetter pers. comm.). Ergatoid queens have been reported in S. humicola (Ogata 1983), and their morphology is very similar to that of the worker, except for larger size, presence of compound eyes and a single ocellus in some but not all gynes. Confirmed alate or apparently dealated gynes are so far known only in undescribed forms from both Old and New World.

Male

Borowiec (2016) - Head: Antennae with 12 segments. Clypeus with cuticular apron. Parafrontal ridges present. Torulo-posttorular complex vertical. Maxillary palps 4-segmented. Labial palps 2-segmented. 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 present. Mesosoma: Pronotal flange not separated from collar by distinct ridge. Notauli present. Transverse groove dividing mesopleuron present. Propodeal declivity reduced, without distinct dorsal edge or margin. Metapleural gland opening absent. Propodeal lobes present. Metasoma: Petiole anterodorsally immarginate, dorsolaterally immarginate, and laterally above spiracle marginate. Helcium in relation to tergosternal 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). Abdominal segment III about half size of succeeding segment IV or less; latter strongly constricted at presegmental portion (binodal 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 absent. Abdominal segment IV 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, and ventrally with left and right arms abutting. Telomere gradually tapering toward apex. Volsella not tapering much toward apex, relatively broad. Penisvalva laterally flattened, at apex hooked ventrally, in Neotropical forms also apparently curving outwards. 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 absent. Cross-vein 2r-rs present, forming base of ‘free stigmal vein’ (2r-rs&Rs·f4–5) in absence of Rs·f3 and 2rs-m. 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, short, not reaching wing margin. Cross-vein 1m-cu in fore wing absent. Cross-vein cu-a in fore wing present, arising from M+Cu and proximal to M·f1. Vein Cu in fore wing absent past M+Cu. 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 present. Abscissa Rs·f1 in hind wing present, longer than 1rs-m. Abscissa Rs·f2 in hind wing present, not reaching wing margin. Cross-vein 1rs-m in hind wing absent or present, about as long as M·f1. 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. Vein Cu in hind wing absent. Vein A in hind wing with abscissa A·f1 present.

Larva

Described for Syscia augustae. Cocoons absent.

References