Vitsika

Endemic to Madagascar, most species inhabit rainforest habitats and are most commonly collected in leaf litter samples. A number of species have been found associated with vegetation. This includes being found in dead and live twigs, in hollow stems and in rotting wood. Overall, the biology of species of Vitsika are all poorly known.

Identification
Bolton and Fisher (2014) - The 14 species of  Vitsika  present a strikingly uniform appearance in terms of sculpture and pilosity, as well as an extremely limited range of standard indices. They obviously represent a very compact single group. Unfortunately, Vitsika workers are currently diagnosed among the myrmicines only by the presence of a unique combination of characters. As with many other myrmicine genera no unique morphological apomorphy can yet be cited. It is defined by its possession of the following characters in combination: mandible with 6 or more teeth; palp formula 5,3; stipital crest strongly present; antenna 12-segmented, with a 3-segmented club; clypeus with an isolated median seta set above a narrow anterior apron; clypeus posteriorly narrowly inserted between the frontal lobes; frontal carinae present and long, extending almost to the posterior margin of the head; antennal scrobes present; mesosomal dorsal outline simple; petiole pedunculate; first gastral tergite does not overlap the sternite on the ventral surface of the gaster; gastral shoulders absent.

This genus is one of a number of closely related Myrmicinae genera - the Eutetramorium group - from Madagascar.

Keys

 * Key to Eutetramorium group genera
 * Key to Vitsika workers
 * Key to Vitsika males

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



Nomenclature

 *  VITSIKA [Myrmicinae: Myrmicini]
 * Vitsika Bolton & Fisher, 2014: 68. Type-species: Vitsika crebra, by original designation.

Worker
Monomorphic myrmicine ants.

Mandible triangular; masticatory margin with 6–8 teeth and longer than the basal margin.

Palp formula 5,3.

Stipes of maxilla with a strong transverse crest; portion of stipes distal to the crest distinctly depressed and concave.

Clypeus with longitudinal rugulae on median portion, two of which may be enhanced to produce a weakly bicarinate appearance; posteriorly moderately narrowly inserted between the frontal lobes (width of clypeus between the frontal lobes about equal to the width of one lobe).

Clypeus with an unpaired median seta that arises just above a narrow anterior clypeal apron.

Clypeus with lateral portions not raised into a shielding wall or sharp ridge in front of the antennal sockets.

Frontal carinae present, divergent posteriorly, extending back almost to the posterior margin of the head.

Antennal scrobes present, above the eye.

Antenna with 12 segments, with an apical club of 3 segments.

Torulus with upper lobe concealed by the frontal lobe in full-face view, or its extreme outer edge just visible.

Eyes present, in dorsal view located slightly to distinctly in front of the midlength of the side of the head capsule.

Head capsule without a median, longitudinal carina; occipital carina conspicuous.

Pronotal humeri angulate to weakly, obtusely dentate in dorsal view.

Promesonotum more or less evenly shallowly convex in profile, not swollen or domed; propodeal dorsum in profile con¬tinues the line of the promesonotum.

Promesonotal suture absent; metanotal groove absent or present.

Propodeum strongly bispinose; propodeal lobes small and rounded.

Propodeal spiracle behind the midlength of the sclerite, in profile well below the dorsal margin, and one spiracle diame¬ter or slightly more in front of the margin of the declivity; one spiracle diameter or less from the apex of the meta¬pleural gland bulla.

Metasternal process absent; a pair of low carina arise anterior to the metasternal pit and diverge posteriorly, one on each side of the pit.

Tibial spurs: mesotibia 0 or 1; metatibia 0 or 1; sometimes the spurs extremely reduced, hardly distinguishable from the setae at the tibial apices.

Abdominal segment 2 (petiole) with a long anterior peduncle, with a dentiform anteroventral process; spiracle situated from slightly behind to distinctly in front of midlength of peduncle.

Abdominal segment 2 node narrow, high-domed to cuneate in profile; ventral surface indented and angled below the node.

Stridulitrum present on pretergite of abdominal segment 4.

Abdominal segment 4 (first gastral) tergite does not broadly overlap the sternite on the ventral gaster; gastral shoulders absent.

Sting simple, strongly developed.

Main pilosity of dorsal head and body consists of simple setae, present and numerous on all dorsal surfaces of head and body. Scapes with elevated pubescence but without standing setae. Dorsal (outer) surfaces of mesotibiae and metatibiae with standing setae present.

Sculpture. Basically similar in all species. Mandibles superficially sculptured to weakly longitudinally costulate; sculp¬ture tends to fade out towards the masticatory margin. Dorsum of head between frontal carinae longitudinally cos¬tulate, the costulae divergent posteriorly; spaces between costulae with reticulate-punctulate ground-sculpture that varies from weak to pronounced. Costulae never form a reticulum anywhere on the head, but a few anastomoses may occur near the posterior margin. Area within scrobe predominantly reticulate-punctulate, sometimes also with a few weak rugulae; above the eye usually with 1–3 longitudinal costulae or rugulae. Dorsum of mesosoma reticulate-rugose, most strongly developed on pronotum. Side of pronotum reticulate-rugose towards the dorsum, more longitudinally rugose on lower half of side. Mesopleuron with sparse (ca 5–7) longitudinal rugae, at least the lower ones oblique; these rugae usually extend onto the metapleuron. Gaster unsculptured.

Queen
Queens are known for all species except obscura. Characters are as in the worker, except for the usual developments of the mesosoma seen in alates. The queens may be alate or ergatoid, or both forms may occur within a single species. It is possible that all species will be found to produce both ergatoids and alates when the species are better represented in collections. Two species (manifesta, suspicax) exhibit morphological intermediates between alate and ergatoid forms, and two species (acclivitas and crebra) appear to be polygynous. The alate queen has three distinct ommatidia and a characteristically large mesosoma with a full complement of flight sclerites; the pronotum is well represented on the dorsal mesosoma, and the mesopleuron has a strong sulcus. Ergatoids have a mesosoma that is usually larger than in true workers but much smaller than in alates. The mesonotum is frequently hypertrophied in ergatoids with respect to the worker caste, and 1–3 ommatidia are usually present, although only a vestigial median ocellus may be remain; there is no transverse sulcus on the mesopleuron. Intermediates between these two extremes exhibit a mesosoma that is alate-like but much smaller in size, usually with most or all sclerites of the pterothorax represented but in a reduced form, fused together, and with no trace of wing attachments; 3 ocelli are always present in these forms. Venation: see under male.

Male
Worker-associated males are known for crebra, breviscapa and labes. In addition, the males of three other species, collected in isolation (in Malaise traps), are present in CASC. Similar in size to the conspecific worker or slightly smaller. Mandible triangular and distinctly dentate, with 5–7 teeth. Palp formula 5,3 (in situ counts). Stipital crest present on maxilla. SI 30–52. Antenna with 13 segments, conspicuously not filiform, characteristically modified. First funicular segment short but not globular, about 0.40–0.60 × the length of the second funicular segment. Funiculus segment 8 (= antennal segment 9) about equal in length to the scape. Funiculus segment 9 (= antennal segment 10) strikingly elongate, 1.45–1.80 × SL, and the funiculus with a kink or angle between the elongate ninth segment and the tenth. The three apical funicular segments (10–12) are also elongate and form a slender club, of which at least the apical segment is longer than SL (sometimes 2 or all 3 apical segments are > SL). Eyes large, located at or in front of the midlength of the sides. Ocelli conspicuous. Occipital carina sharp but not forming a raised crest. Mesoscutum in profile strongly overhangs the pronotum, the latter not visible in dorsal view. Mesotibia and metatibia each with a single, simple spur. Notauli variably developed, from vestigial to having anterior arms present. Mesopleuron with a transverse sulcus present. Propodeum usually unarmed and rounded, but in some the posterodorsal angle is reinforced by a carina, or the angle projects as a low, obtuse tooth; propodeal lobes rounded. Petiole in profile slightly longer than postpetiole. Petiole with an anterior peduncle, the spiracle at, or slightly in front of, the midlength of the peduncle, well in front of the level of the low, rounded node. Subpetiolar process minute to absent. Parameres large. Cerci present. Pilosity simple everywhere.

Forewing venation (based on males of six species, and alate queens of crebra and miranda). Rs·f4–5 does not meet R·f3 on anterior margin of wing (= marginal cell open). 2rs-m absent. 1m-cu present. Fusion of Rs+M extended distally, so that 1m-cu arises from Rs+M, not from M. Rs·f3 present (Rs+M divides into Rs·f3 and M·f3-4 proximal of the junction with 2r-rs). M·f3-4 is usually represented only by a short stub (entirely absent in the single alate queen of miranda). First discal cell small, its anterior margin (Rs+M) only about half the length of its posterior margin (Cu·f1-2). A·f2 absent or a mere stub distal to cu-a; the latter is retracted and arises from M+Cu, proximal of the point where it divides into M·f1 and Cu·f1-2.