Zatania

Identification
LaPolla et al. (2012) - Zatania workers are most likely to be confused with Old World Prenolepis workers. At present, Zatania is only known from the Greater Antilles and Central America, and Prenolepis is absent from these areas, so Zatania workers could seemingly be separated from Prenolepis workers based on geography. As other ant genera, however, have been found to have a disjunct distribution between Asia and Central America (e.g. Longino & Hartley, 1994), it is possible that Zatania does in fact occur in Asia. The Asian tropics, where Prenolepis reaches highest species diversity, have been poorly collected, and as new collections are made, the discovery of Zatania in Asia would not be surprising. The main diagnostic features that separate Zatania and Prenolepis workers are found in the head and mesothorax. Prenolepis workers generally have a round head, with very indistinct posterolateral corners, whereas Zatania workers have a rectangular head, with more distinct posterolateral corners. The one exception is found in Zatania gloriosa, which has a rectangular head, but also has very indistinct posterolateral corners. Prenolepis also always have a mesothorax that is constricted immediately behind the pronotum. This condition is observed among the extant members of Zatania in Zatania albimaculata, Zatania gibberosa and Zatania karstica (the fossil species Zatania electra also has constricted mesothorax). In these Zatania species, however, the eyes are small relative to the size of the head, and they are relatively flat, whereas in most Prenolepis the eyes are larger relative to the size of the head and distinctly convex. In species such as Prenolepis imparis, where the eyes are not distinctly convex, their head is still distinctly rounded, thereby placing it within Prenolepis.

The main difficulty in distinguishing between the various lineages within the Prenolepis genus-group at the morphological level arises from the fact that, in several groups, a similar morphological form is observed among workers, confounding the use of worker morphology as a basis for generic level recognition. An elongated worker mesosoma is present in Euprenolepis, Paratrechina and Prenolepis, as well as in the new genus described here. Accompanying this elongated mesosoma are elongated scapes and legs, and typically a distinct constriction of the mesosoma behind the pronotum. To a lesser degree, this suite of morphological traits is seen in a few species of Pseudolasius and Nylanderia as well. The reliance on worker-based taxonomy has hindered the discovery of this new lineage, and it remains a possibility that other lineages are currently undiscovered within the Prenolepis genus-group, based on the level of worker morphological convergence observed. Upon closer inspection, differences in worker morphology can usually be observed, but it is often difficult to ascertain their relative phylogenetic importance a priori. An example can be seen in separating Pseudolasius and Euprenolepis, as both are distinct lineages based on molecular data. With closer  examination it was found that the mandalus of the mandible in each genus was different (LaPolla, 2009), but without the molecular phylogenetic results it would have been difficult to assess if this morphological difference represented a true synapomorphy for Euprenolepis.

The males of Zatania, however, do provide a series of diagnostic morphological features for the genus. A notable difference between males of P. imparis and Zatania is observed in the antennal scapes. Zatania males possess long scapes compared with the short scapes of P. imparis. Zatania males possess long, narrow parameres, digiti and cuspi that meet dorsally, digiti that are shorter than the aedeagal valves (in P. imparis the digiti are much longer than the aedeagal valves), and robust, distinctly shaped digiti. These genitalic characters are putatively morphological synapomorphies for the genus. It is encouraging that male-based morphology provides a means to indentify some clades within the Prenolepis genus-group that are highly supported by our molecular data. The problem of course remains that for many species males are unknown. Zatania males are distinctive in several ways, the most obvious being their elongated scapes and legs, and the structure of the genitalia. It would be prudent for future morphologically based research of this genus-group to include males whenever possible.

Zatania Species Key

Key to Prenolepis Group Genera

Nomenclature

 *  ZATANIA  [Formicinae: Prenolepis genus group]
 * Zatania LaPolla, Kallal & Brady, 2012: 204. Type-species: Paratrechina (Nylanderia) cisipa, by original designation.

Worker
Monomorphic, medium-sized (2–3 mm in total length) formicine ants, ranging in colour from brownish yellow to brown and reddish brown. Head with pubescence, and erect setae found along head margin; medially erect setae roughly paired, extended through medial portion of clypeus. Cuticle sculpturing variable; in some species opaque and slightly rugose, as in Zatania albimaculata; in other species cuticle smooth and shining as in Zatania cisipa and Zatania gloriosa.

Antennae 12-segmented; scapes long, surpassing posterior margin by at least the length of the first four funicular segments. Scapes with either a dense layer of short erect setae and/or a layer of appressed setae that in some species is fairly scattered. Head longer than wide [cephalic index well below 100 (our recorded range, 75–87)].

Eyes medium to large, relative to head size; in Z. cisipa and Z. gloriosa eyes distinctly convex; three small, indistinct ocelli present.

Mandibles typical for a Prenolepis genus-group taxon, with five or six teeth: Z. albimaculata, Zatania gibberosa and Zatania karstica have five teeth; Z. cisipa and Z. gloriosa have six teeth; however, the tooth between the basal tooth and tooth 4 is much smaller than the other teeth, and is often missing, leaving a diastema between the basal tooth and tooth 4, effectively making the mandible five-toothed. Palps 6:4 segmented and long (at least as long as head).

Mesosoma distinctly elongated; in profile pronotum and mesonotum long; pronotum rises at less than 45◦ angle to mesonotum; in profile roughly triangular in shape at segment dividing pronotum and mesonotum; in some species mesonotum constricted immediately behind pronotum (Z. albimaculata and Zatania electra  possess the most extreme example of this character state); between 4–10 pronotal setae present.

Propodeum variable: in Z. albimaculata, Z. electra†, Z. gibberosa and Z. karstica, propodeum dorsal face dome-like and higher than remainder of mesosoma; in Z. cisipa and Z. gloriosa dorsal face gently rounded and not higher than remainder of mesosoma. In Z. gibberosa dorsal face with abundant short erect setae; in other species, dorsal face with only scattered or no erect setae. Petiole cuneate, broadly rounded dorsally and not surpassing height of propodeum.

Legs notably long; in darker coloured species, tarsi lighter in colour than remainder of leg.

Gaster robust, densely covered with erect setae and in some species with layer of pubescence.

Queen
Queens generally have the same coloration (although they are typically darker), setation and pubescence patterns as seen in workers.

Male
(males only examined in Zatania cisipa, Zatania electra, Zatania gibberosa and Zatania gloriosa)

Coloration similar to workers, but generally lighter overall. Cuticle surface, pubescence and setation patterns generally follow worker morphology.

Antennae 13-segmented; scapes long, as in workers, with similar pubescence and setation patterns.

Head shape variable; in Z. cisipa and Z. gloriosa compound eyes very large and convex, taking up most of lateral margin, with three very large ocelli; in Z. gibberosa compound eyes and ocelli considerably smaller, and head more similar to worker in general shape.

Mandibles in Z. cisipa and Z. gloriosa with prominent, pointed apical tooth; remainder of masticatory margin smooth, with indistinct, rounded basal angle that seamlessly blends into inner mandibular margin. In Z. gibberosa mandible also with prominent, pointed apical tooth, but masticatory margin serrated into generally indistinct denticles, most prominent and tooth-like immediately behind apical tooth; basal angle rounded, but more distinct than observed in Z. cisipa and Z. gloriosa; as in workers, palps 6:4 segmented and long.

Mesosoma robust, with small collar-like pronotum, overarched by rounded and prominent mesonotum; dorsal and declivitous faces of propodeum difficult to distinguish; propodeum linear in profile, at approximately a 45◦ angle.

Legs long as in workers.

Gaster generally similar to workers. Genitalia variable by species, but with some generally similar characteristics: parameres elongate and narrow; digiti and cuspi meet dorsally; digiti and cuspi shorter than aedeagal valves; digiti and cuspi very similar in overall shape and conformation.

Etymology
The derivation of the genus name is a combination of the Greek prefix za (very) and tany (long), in reference to the long scapes, mesosomata and legs of species in this genus; it is a feminine noun.