Syllophopsis

Syllophopsis is a taxonomically difficult and possibly polyphyletic genus of tiny, inconspicuous ants. Bolton (1987) noted the Afrotropical species are: "very widely distributed within the region. All are minute and constitute a minor fraction of the extensive leaf litter and topsoil fauna of the region."

Santschi (1915) described Syllophopsis as a subgenus of Monomorium. Some subsequent authors followed this designation, whereas others considered Syllophopsis to be a distinct genus. Still other authors designated these ants as belonging to the Monomorium fossulatum group (e.g. Bolton 1987; Sharaf 2007) or the Monomorium hildebrandti group (e.g. Heterick 2006; Sharaf and Aldawood 2013). Ward et al. (2015) designated Syllophopsis as a distinct genus. Recent genetic analyses, however, suggest that Syllophopsis, as currently constituted, may be polyphyletic, with two distinct clades: one closely related to Monomorium and the other closely related to the newly resurrected genus Chelaner (Sparks et al. 2019). A comprehensive revision encompassing all named Syllophopsis taxa is needed. (Wetterer & Sharaf, 2021)

Identification
Aldawood (2016) - The worker caste of Syllophopsis is readily identified by the combination of the following characters (Bolton 1987):
 * monomorphic
 * antennae 12-segmented terminating with a 3-segmented club
 * median clypeal portion distinctly longitudinally bicarinate that project anteriorly as a pair of blunt teeth
 * eyes tiny with one or two ommatidia
 * promesonotal suture absent
 * metanotal groove impressed, sometimes less-developed but distinct
 * propodeal dorsum making a minute dent with declivity.

In many species, propodeal outline obtusely angulate; petiole pedunculate, with a high and rounded node; postpetiole node smaller and lower than petiolar node in profile.

Wetterer & Sharaf (2021) - Syllophopsis workers are small, monomorphic, and yellow to light brown in colour, and can be recognised by the following characters in the workers (Bolton 1987; Fisher and Bolton 2016):
 * 12-segmented antennae with well-defined three-segmented terminal clubs
 * eyes usually minute with one or two ommatidia
 * head in full-face view with a narrow clypeus and close antennal sockets
 * propodeum profile denticulate or angulate

Workers of Syllophopsis species resemble small Solenopsis thief ants – from which, however, they can be easily distinguished by the 12-segmented antenna that terminates in a 3-segmented large club, and the obtusely angled or denticulate profile between propodeal dorsum and declivity.

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

Biology
Syllophopsis sechellensis is known to forage both on and under the ground (Eguchi & Bui 2009).

Nomenclature

 * arnoldi. Syllophopsis arnoldi Santschi, 1921c: 120, fig. 2d,e (w.) SOUTH AFRICA.
 * [Note: genus misspelled as Syllopsis in original description title; correctly spelled in legend of fig. 2.]
 * Type-material: 4 syntype workers.
 * Type-locality: South Africa: Natal, Mfongosi (Jones).
 * Type-depository: NHMB, SAMC.
 * [Junior secondary homonym of Monomorium arnoldi Forel, 1913a: 137.]
 * Status as species: Ettershank, 1966: 101.
 * Replacement name: Monomorium (Syllophopsis) jonesi Arnold, 1952a: 465.
 * [Note: as the replacement name jonesi was proposed before 1960 (when both arnoldi taxa were included in Monomorium), the replacement name retains validity under ICZN Art. 59.3. Therefore the priority awarded by Ward, et al. 2015: 73, is incorrect.]
 * boerorum. Monomorium (Syllophopsis) modestum var. boerorum Santschi, 1915c: 260, fig. 9 (w.) SOUTH AFRICA.
 * Type-material: syntype workers (number not stated).
 * Type-locality: South Africa: Transvaal, Pretoria (no collector’s name).
 * Type-depository: NHMB.
 * [Junior primary homonym of Monomorium minutum var. boerorum Forel, 1910e: 442.]
 * Status as species: Santschi, 1921c: 120 (in key).
 * Replacement name: Monomorium (Syllophopsis) modestum var. transwaalensis: Emery, 1922e: 175.

Taxonomic Notes
Aldawood (2016)- The myrmicine ant genus Syllophopsis was established by Santschi (1915) for the species Syllophopsis modestum Santschi, 1914. The genus now includes 21 valid species distributed in the Afrotropical and Malagasy regions (Bolton, 1987; Heterick, 2006), and two widespread species occurring in the Indo-Australian region and on the islands of the Pacific and Indian oceans (Wilson & Taylor, 1967).

In his comprehensive review of the Solenopsis genus-group and the Afrotropical fauna of the genus Monomorium, Bolton (1987) synonymized Syllophopsis under Monomorium, recorded seven species and described three new African species, Syllophopsis malamixta and Syllophopsis thrascolepta from Ivory Coast and Syllophopsis sersalata from Rwanda. These 10 species were included in the  Monomorium fossulatum-group. In a revision of the Malagasy Monomorium, Heterick (2006) included the species of the M. fossulatum-group with the hildebrandti-group. Recently, Syllophopsis was resurrected as a valid genus by Ward, Brady, Fisher, and Schultz (2014).

The only treatment of Syllophopsis for the Arabian Peninsula was by Sharaf & Aldawood (2013), recording the genus for the first time from southwestern Saudi Arabia by the new species, Syllophopsis kondratieffi based on the worker caste. In addition, a key was provided for the species of Syllophopsis known from the Afrotropical region. Recently, Sharaf, Fisher, Collingwood, and Aldawood (unpublished data) reported the genus from Socotra Island (Yemen) for the first time by an undescribed species. In North Africa, Sharaf (2007) described Syllophopsis dentata form the Nile Valley, upper Egypt.

Worker
Bolton (1987) fossulatum group (There is currently no published diangnosis/decription of the genus that is based on an examination of all the contemporary species that belong to the genus. The following text is from Bolton (1987) and was based on what was then thought to be a Monomorium species group, as explained above by Aldawood.): Monomorphic, with some size variation but without allometric variation. Mandibles unsculptured except for hair-pits, armed with 4 teeth which decrease in size from apex to base and which usually have the masticatory margin markedly oblique. Palp formula 2,2 (all species). Anterior clypeal margin without a pair of projecting teeth. Median portion of clypeus narrow and sharply raised, weakly bicarinate at least posteriorly, the carinae tending to fade out anteriorly. Median portion of clypeus very narrow posteriorly, distinctly narrower than the maximum width of either frontal lobe where it passes between them; frontal lobes and antennal insertions consequently very close together (Fig. 93). Eyes minute and point-like, of only one or two ommatidia and situated at the midlength of the sides; maximum diameter of eye only 0.05-0.08 x HW. Antennae with 12 segments terminating in a large club of 3 segments. Head relatively narrow and scapes of moderate length, CI 72-85, SI 90-110. Cephalic dorsum unsculptured except for hair-pits. Lateral portions of clypeus and area immediately behind them, and area around antennal fossae, without striolate or costulate sculpture. Propodeum without transverse sculpture dorsally, with the spiracle circular to subcircular; propodeal dorsum meeting declivity in an obtuse angle or weakly denticulate at the junction. Petiole with a long anterior peduncle, the petiolar spiracle at the node or immediately in front of the anterior face of the node when viewed in profile. Fine standing hairs present on all dorsal surfaces of head and body except for the propodeum, where they are usually sparse or absent. (Workers examined: all included in this study plus the extralimital species Monomorium fossulatum (=Syllophopsis sechellensis) and Syllophopsis australica.)

Queen
Bolton (1987) fossulatum group (There is currently no published diangnosis/decription of the genus that is based on an examination of all the contemporary species that belong to the genus. The following text is from Bolton (1987) and was based on what was then thought to be a Monomorium species group, as explained above by Aldawood.): Diagnosis as worker but females considerably larger than conspecific workers and with much larger eyes. Ocelli present and alitrunk with full complement of flight sclerites. HW approximately equal to the maximum width of the mesoscutum, the latter extensive and slightly longer than broad, with parapsidal grooves absent or at most extremely faint. Pronotum not forming part of dorsal alitrunk; in dorsal view only the extreme anterolateral corners of the pronotum can be seen. Axillae large, triangular in dorsal view and the distance separating them is much less than the length of either axillary sclerite. Forewing with cross-vein m-cu present (Syllophopsis cryptobia). (Females examined: cryptobia, Syllophopsis malamixta, Syllophopsis sersalata, Syllophopsis australica.)