Myrmisaraka

The genus is comprised of two ground dwelling species that have also been found foraging in low vegetation. 'Myrmisaraka'' is endemic to Madagascar.

Identification
1 In the vast majority of Myrmisaraka workers there are two setae within the notch on the anterior clypeal margin. They are short and fine, located close together, one on each side of the midpoint of the margin. Much more rarely, there is only a single seta present. In some instances the seta is off-centre and obviously indicates that its twin has fallen off and been lost. However, in a very few specimens there is a single seta that is definitely median. The occurrence of this variation within a species is uncommon in myrmicines, having been recorded elsewhere only in a few species of Stenamma and Rogeria (Bolton, 2003; Branstetter, 2009).

2 This small genus resembles the very widespread Aphaenogaster in habitus. The following characters distinguish the two.

In Myrmisaraka a transverse crest is present on at least the mesial half of the stipes; a distinct subpetiolar process is present that appears as a sharp tooth in profile but as a transverse crest in ventral view; the propodeal spiracle is large and relatively low on the side, closer to the apex of the metapleural gland than to the dorsal outline; the postpetiole is elongate, dorsoventrally flattened in profile and very broad in dorsal view; the sting is strongly developed and conspicuous. In addition, the pair of setae that straddle the midpoint of the anterior clypeal margin are short, very fine, and are closely approximated basally. Finally, the ventral metathorax has a posteriorly divergent pair of carinae, that arise just anterior of the metasternal pit, diverge posteriorly, and terminate at the inner margins of the metacoxal annuli.

The corresponding states in Aphaenogaster are: a transverse crest is usually absent from the stipes (weaky visible in a few species, strong only in Aphaenogaster relicta from Haiti, which may not be properly referable to this genus); subpetiolar process is absent; propodeal spiracle is small and relatively high on the side, usually closer to the dorsal outline than to the apex of the metapleural gland; postpetiole is not elongate nor dorsoventrally flattened in profile (usually strongly convex and dome-like), and is not broad in dorsal view; the sting is extremely weakly developed and usually invisible. In addition, the pair of setae that straddle the midpoint of the anterior clypeal margin are long and stout, markedly separated basally. The ventral metathorax does not show a divergent pair of carinae such as are described above. The validity of this final observation needs confirmation as the number of Aphaenogaster species examined is small, but does include the Madagascan Aphaenogaster swammerdami.

The Malagasy fauna includes three Aphaenogaster species, all confined to Madagascar itself, Aphaenogaster friederichsi, Aphaenogaster gonacantha and A. swammerdami. The second and third of these belong to the old subgenus A. (Deromyrma), principally characterised by the extension of the posterior portion of the head into a long, narrow, constricted neck. Because of this striking development these two species can not be confused with Myrmisaraka. A. friederichsi does not exhibit this modification, but differs from Myrmisaraka in all the characters mentioned above.

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

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



Castes
Males taken in association with workers are unknown. However, there is one male-based species (2 specimens) from Prov. Toamasina, Betampona Reserve, BLF 19594-49, CASENT0143821, and BLF 19594-55, CASENT0145230 that are linked by DNA structure to Myrmisaraka producta (B.L. Fisher, unpublished). A second male-based species (1 specimen), Prov. Toamasina, Ambodiriana, BLF 12838, CASENT0068183 is congeneric with the male of producta but apparently not linked to brevis, the other worker-based species included here.

The two different male forms are easily distinguished as one has much larger eyes than the other. M. producta: eyes larger, in full-face view the maximum length of the eye is 0.64 × HL; in profile the shortest distance from the dorsal margin of the eye to the base of the posterior ocellus is less than the vertical height of the ocellus. Second male form (Ambodiriana): eyes smaller, in full-face view the maximum length of the eye is 0.47 × HL; in profile the shortest distance from the dorsal margin of the eye to the base of the posterior ocellus is greater than the vertical height of the ocellus.

Nomenclature

 *  MYRMISARAKA [Myrmicinae: Myrmicini]
 * Myrmisaraka Bolton & Fisher, 2014: 33. Type-species: Myrmisaraka producta, by original designation.

Worker
Monomorphic myrmicine ants.

Mandible triangular, masticatory margin with 9–11 teeth, longer than basal margin.

Palp formula 5,3.

Stipes of maxilla with a partial transverse crest, strongest near mesial margin, petering out laterally.

Clypeus posteriorly moderately broadly inserted between the frontal lobes (width of clypeus between the lobes greater than width of one of the lobes); median portion of clypeus with 4–6 fine longitudinal rugulae, the median longitu¬dinal strip unsculptured (no median carina present); anterior clypeal margin with a small median notch.

Clypeus usually with a pair of closely approximated short, fine setae, one on each side of the midpoint, within the median notch; rarely with only a single seta present (see comment 1, below).

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

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

Antennal scrobes absent.

Antenna with 12 segments, with a 3-segmented to weakly 5-segmented apical club.

Torulus with upper lobe visible in full-face view.

Eyes present, relatively large, located at about the midlength of the head capsule.

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

Pronotal humeri weakly angulate in dorsal view.

Pronotum plus anterior mesonotum swollen and distinctly convex in profile, almost dome-like; dorsalmost point of promesonotum on a considerably higher level than propodeal dorsum.

Promesonotal suture absent; metanotal groove almost effaced.

Propodeum strongly bispinose; propodeal lobes small and rounded.

Propodeal spiracle large and conspicuous, at about the midheight and midlength of the sclerite, far in front of the margin of the declivity and separated from apex of metapleural gland bulla by about the spiracle’s diameter.

Metasternal process absent; a posteriorly divergent pair of weak carinae present that arise just anterior of the metasternal pit, diverge posteriorly, and terminate at the inner margins of the metacoxal annuli.

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

Abdominal segment 2 (petiole) with a long, narrow anterior peduncle; spiracle at the midlength of the peduncle.

Subpetiolar process in profile a small spiniform tooth.

Abdominal segment 3 (postpetiole) dorsoventrally flattened in profile, the sternite convex; tergite very broad in dorsal view.

Stridulitrum present on pretergite of abdominal segment 4.

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

Sting strongly developed, simple.

Main pilosity of dorsal head and body: simple and fine, present on propodeal dorsum.

Queen
Ergatoid in producta, unknown in brevis. The ergatoid lacks ocelli and mostly matches the worker description. The mesonotum is enlarged by comparison with the worker, and its margins are more stongly defined. The promesonotal suture forms a broad, shallow impression and the posterior mesonotum is defined in profile. Propodeal spiracle separated from apex of metapleural gland bulla by less than the spiracle’s diameter. Peduncle of petiole shorter and stouter than in worker. Postpetiole and gaster in dorsal view broader than in worker, as discussed under producta queen.

Male
Known only for M. producta. Slightly smaller than workers. Mandible triangular and strongly dentate, with 9–10 teeth. Palp formula 5,3 (in situ count). Clypeus with an anterior apron. Antenna with 12 segments, long and filiform. SI 37–44. First funicular segment short, not globular, about one third the length of the second funicular segment. In full-face view eye either located behind midlength of head capsule, or occupying most of the side. Ocelli conspicuous. Mesotibia and metatibia each with a single simple spur. Notauli very reduced or absent, at most the anterior arms discernible as extremely feeble impressions. Mesopleuron with a marked transverse sulcus. Propodeum armed with a pair of small, triangular teeth, the spiracle at about the midlength of the sclerite; propodeal lobes rounded. Petiole with an anterior peduncle, the spiracle at about the midlength of the peduncle, well in front of the level of the node. Subpetiolar process present, small. Parameres large. Cerci present. Pilosity slender, fine and dense everywhere.

Forewing venation. 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). A·f2 long, not merely a stub distal of cu-a, the latter is retracted toward the wing base and arises from M+Cu, proximal of the point where it divides into M·f1 and Cu·f1–2.