Malagidris

This small genus ( species) is endemic to Madagascar. These are ground nesting ants, with their colonies found in soil, rotten wood or moss, with foragers that are active in the leaf litter and on the ground.

Identification
Bolton and Fisher (2014) - The larger, more gracile species (e.g. alperti, galokoa, jugum, sofina) of Malagidris are remarkably convergent on the widely distributed genus Aphaenogaster. However, all species of Malagidris have two critical features never exhibited by Aphaenogaster species. First, the midpoint of the anterior clypeal margin of Malagidris has a single, stout, unpaired seta. In Aphaenogaster there is always a conspicuous pair of setae, one on each side of the midpoint of the anterior clypeal margin. Second, Aphaenogaster species do not have the characteristic structure of the anteroventral peduncle of the petiole, as described under the definition of Eutetramorium group. In addition to these, Malagidris always has the following: a transverse crest present on the stipes of the maxilla; a 3-segmented antennal club; a subpetiolar process present; a strongly developed sting; the anterior clypeal margin convex at the midpoint. In Aphaenogaster, by contrast, the stipes usually lacks a crest (a crest is incompletely and weaky developed in a few species, strong only in A. relicta  Wheeler & Mann, from Haiti, which may not be properly referable to Aphaenogaster), usually has a 4-segmented antennal club (5-segmented to gradually incrassate in some species but never 3-segmented), lacks a subpetiolar process, has a very weakly developed or vestigial sting, and usually (but not always) has the midpoint of the anterior clypeal margin concave or indented.

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

Nomenclature

 *  MALAGIDRIS [Myrmicinae: Myrmicini]
 * Malagidris Bolton & Fisher, 2014: 16. Replacement name for Brunella Forel, 1917: 234. [Junior homonym of Brunella Smith, G.W. 1909: 87 (Crustacea).]
 * BRUNELLA [junior homonym, see Malagidris]
 * Brunella Forel, 1917: 234. Type-species: Aphaenogaster belti, by monotypy.
 * Brunella junior synonym of Atopula: Emery, 1924d: 242; Donisthorpe, 1943f: 629.
 * Brunella junior synonym of Aphaenogaster: Bolton, 1982: 364; Bolton, 1994: 106.
 * Brunella revived from synonymy: Bolton & Fisher, 2014: 16.

Bolton and Fisher (2014):

The type-species of this genus, belti (Forel, 1895), has had a moderately varied taxonomic history. It was originally described in the genus Aphaenogaster Mayr (1853), even though Forel remarked on its 3-segmented antennal club, rather than 4 as is usual in that genus. This character, coupled with the presence of angulate humeri and a queen with a depressed mesosoma, caused Emery (1915a: 68) to exclude belti from Aphaenogaster  and transfer it to Atopula Emery (1912). Forel (1917: 234) decided that Atopula was artificial, “composed of disparate species,” and established the genus Brunella to include only belti. The component species of Atopula were later dispersed to other genera by Bolton (1976: 362), who retained genus Brunella as its “affinities are unclear.” Later however, Bolton (1982: 341) synonymised Brunella under Aphaenogaster, thus returning belti to its original generic combination.

Extensive recent sampling of the Madagascan ant fauna by Brian Fisher and associates has made it clear that this synonymy was incorrect. The discovery of several species referable to Forel’s Brunella has allowed the diagnosis of a distinct group of Madagascan endemics, which are convergent in some characters with Aphaenogaster but certainly not congeneric with it. The final act of this history has been the realisation that Brunella Forel (1917) is the junior homonym of a crustacean genus Brunella G.W. Smith (1909), from Tasmania. No replacement name was essential for Brunella Forel while it was a junior synonym, but now that it is revived from synonymy a replacement name is necessary: Malagidris nom. n.

Worker
Monomorphic myrmicine ants.

Mandible triangular; masticatory margin with 8–13 teeth, longer than the basal margin.

Palp formula 5,3.

Stipes of maxilla with a weak transverse crest.

Clypeus posteriorly moderately broadly inserted between the frontal lobes (width of clypeus between the lobes as great as or greater than width of one of the lobes); median portion of clypeus longitudinally costulate, not bicarinate.

Clypeus with a stout unpaired seta at the midpoint of the convex anterior margin.

Frontal carinae short, restricted to well defined but narrow frontal lobes.

Antennal scrobes absent.

Antenna with 12 segments, with an apical club of 3 segments that may be very slender.

Torulus with upper lobe visible in full-face view; maximum width of torulus lobe is just posterior to the point of maximum width of the frontal lobes.

Eyes present, located in front of the midlength of the head capsule in full-face view.

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

Promesonotal suture absent; pronotal humeri weakly angulate.

Pronotum plus anterior mesonotum swollen and distinctly convex in profile; dorsalmost point of promesonotum at a consid¬erably higher level than the long propodeal dorsum.

Propodeum bispinose; propodeal lobes rounded.

Propodeal spiracle behind midlength of sclerite, at about midheight of side of propodeum and far in front of the margin of the declivity; spiracle separated from apex of metapleural gland bulla by at least one spiracle diameter.

Metasternal process obsolete, at most a narrow crest on each side of the metasternal pit, each crest sometimes extended pos¬teriorly as a narrow carina.

Legs long and slender.

Tibial spurs: mesotibia 1; metatibia 1, both simple.

Abdominal segment 2 (petiole) with a long, slender anterior peduncle; spiracle slightly in front of the midlength of the peduncle.

Abdominal segment 2 node short, rounded to subconical in profile.

Subpetiolar process an anteroventral denticle.

Abdominal segment 3 (postpetiole) elongate, not dorsoventrally flattened, not markedly broader than high; ventral surface in profile flat to shallowly convex.

Stridulitrum present on pretergite of abdominal segment 4.

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

Sting strongly developed, simple.

Main pilosity of dorsal head and body: simple, often sparse, usually absent from propodeal dorsum.

Queen
This caste is alate in belti, ergatoid in alperti, jugum and sofina, and remains unknown in dulcis and galokoa. The alate queen matches the description of the worker except for its conspicuous ocelli and the structure of the enlarged mesosoma, where there is a full complement of flight sclerites and a broad sulcus across the mesopleuron. The ergatoid forms match the definition of the worker but with ocelli variably developed. In alperti and the single known ergatoid of jugum ocelli are absent, although a vague pit-like depression in one alperti ergatoid may indicate the last vestige of the median ocellus. Among the known ergatoids of sofina some retain three distinct ocelli, while others exhibit only a reduced median ocellus. The mesonotum is somewhat larger and better defined than in the worker, with a fully fused but more obvious promesonotal suture across the dorsum. The mesopleuron shows a reduced or absent transverse sulcus. The propodeal spines are shorter and stouter than in the respective workers, the postpetiole is more swollen and the gaster is more voluminous. Venation: see under male.

Male
Males taken in association with workers are known for alperti, belti, jugum and sofina. In addition, males of two more species that appear to belong in this genus are known. One of them is tentatively associated with dulcis here, but this remains to be confirmed; the other does not associate with any known worker but appears morphologically closest to jugum, it is discussed there. Slightly smaller than conspecific worker. Mandible triangular and strongly dentate, with 6–11 sharp teeth. Palp formula 5,3. Stipital crest present on maxilla. Antenna with 13 segments, long and filiform. SI 42–79. First funicular segment short, not globular, about one quarter to one half the length of the second funicular segment. In full-face view eye located in front of midlength of head capsule. Ocelli conspicuous. Occipital carina sharp, forming a distinct crest. Mesotibia and metatibia each with a single simple spur. Notauli very reduced or absent. Mesopleuron with a marked transverse sulcus. Mesoscutum convex in profile, the mesoscutum and mesoscutellum elevated, much higher than the propodeal dorsum, which is depressed and slopes downward posteriorly. Propodeum unarmed, the spiracle high on the side and at about the midlength, or slightly in front of the midlength, of the sclerite; propodeal lobes conspicuous, rounded. Petiole with a long anterior peduncle and a low node, the spiracle at or behind the midlength of the peduncle, but in front of the level of the node. Subpetiolar process present, small. Parameres large. Cerci present.

Forewing venation (based on males as available belti queen specimens are dealate). 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 absent (Rs+M divides into Rs·f4–5 and M·f3–4 at or distal of the junction with 2r-rs). A·f2 a mere stub distal of 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.