Strumigenys arnoldi-group

Bolton, B., 2000, The ant tribe Dacetini. With a revision of the Strumigenys species of the Malgasy Region by Brian L. Fisher, and a revision of the Austral epopostrumiform genera by Steven O. Shattuck., Memoirs of the American Entomological Institute 65, pp. 1-1028 : 627-628

arnoldi-group

DIAGNOSIS OF WORKER

Apical fork of mandible with 2 teeth; always with one long preapical tooth. In some species a second (distal) preapical tooth or denticle is present, between the long (proximal) preapical tooth and the apicodorsal tooth; when present the distal preapical tooth is often weaker on the left mandible than on the right. Mandible in full-face view short (MI 27 - 47), narrow, linear and outcurved in full-face view; the dorsum, proximal of the basalmost tooth, slightly concave.

Antenna usually 6 - merous with funicular segments 2 and 3 small and often difficult to discern, but antenna 4 - merous in micrans, schuetzi, lutron , levana .

Leading edge of scape a dorsoventrally flattened convex lamella.

Eye very small or vestigial, usually with 4 or less ommatidia.

Upper scrobe margins in full-face view widely divergent behind the frontal lobes.

Ventrolateral margin of head without trace of a preocular notch, the margin continuous in front of the eye. Ventral surface of head without a preocular transverse groove but postbuccal groove is distinct.

Promesonotum flat to slightly convex dorsally and bluntly marginate dorsolaterally.

Spongiform appendages of petiole usually well developed into a ventral curtain (narrow strip in abdera ); lateral lobes present. Postpetiole with lateral and ventral lobes. Lamella on propodeal declivity usually well developed into a wide strip below the triangular propodeal spines (narrow in charino , micrans, mold).

Pilosity. Pronotal humeral hair absent or present. Apicoscrobal hair absent. Head with curved spatulate to spoon-shaped or orbicular hairs present on dorsum of head behind clypeus at least on anterior half (absent in abdera ), anterior clypeal margin, lateral clypeal margin, upper scrobe margin (curved anteriorly) (short, simple appressed hairs in abdera ), and leading edge of scape. Dorsum of head without erect hairs or with a transverse row of 4 hairs close to the occipital margin { abdera , alapa , charino , levana , lutron , manga , micrans, mola). Mesonotum without erect hairs, or with one pair on the mesonotum ( abdera , alapa , lutron , manga , micrans, mold) or with two pairs { levana ). Dorsal surface of postpetiole, and gaster with short filiform to narrowly clavate hairs; entire body usually lacking flagellate hairs.

Sculpture. Fine dense reticulate-punctate to reticulate-granulate sculpture blankets the entire dorsum of the head; the pronotum reticulate-punctate and occasionally with longitudinal costulae; remainder of the dorsal alitrunk reticulate-punctate (propodeum not reticulate-punctate in manga ); petiole with dense reticulate-punctate sculpture or with faint reticulate-punctate sculpture that is almost effaced. Gaster unsculptured except for basigastral costulae.

Glands. Scape gland absent { bathron , charino , dolabra , lutron , manga , micrans, mola, schuetzi, toma ) or visible as a elongate patch near apex of ventral scape ( abdera , alapa , heliani , levana ). Femoral and tibial gland bullae absent. Gland at base of calcar conspicuous. Tarsal glands absent { alapa , bathron , toma ) or visible on at least first three tarsi of fortarsi, decreasing in size from basitarsus where it is elongate to the third tarsal segment where it is oval. Mesopleural gland visible and set in a circular notch.

In the Malagasy region members of this group are most similar to species of the emmae-, adsita- and <fem-groups but differ in mandibular dentition and hairs on upper scrobe margin. The apicoscrobal hair is absent (present in emmae ); apical fork of mandible is never composed of 3 spiniform teeth as in adsita-group and mandibles are symmetric, each with either with 3 or 4 teeth (asymmetric in dexis-group ).

In addition, the arnoldi-, emmae-, and adsita-groups can be distinguished from the dexis-gwup by the following characters: eye always small to minute (usually with 4 or less ommatidia) and the lower scrobe margin rounded, never forming a sharp ridge with ventral surface of head. In the dexis-group the eyes are usually conspicuous, never with 4 or less ommatidia, but if eyes small then the lower scrobe margin forms a sharply marginate ridge with ventral surface of head.

The arnoldi-group is also very speciose in the Afrotropical region (see there). The group diagnosis above is somewhat modified from the Afrotropical, to give a best representation of the Malagasy fauna. Within this region members of the group fall into four discrete complexes of related species.

1 abdera-complex ( abdera , bathron , charino , heliani , manga , mola). Right and left mandible each with a spiniform proximal preapical tooth and a smaller distal preapical tooth or denticle; distal preapical is weakest on left mandible and may be a minute denticle. Antenna with 6 segments.

2 alapa-complex ( alapa , dolabra , toma ). Right and left mandible each with one spiniform preapical tooth, without preapical denticles more distally. Antenna with 6 segments.

3 lutron-complex ( levana , lutron , micrans). Right and left mandible each with a spiniform proximal preapical tooth and a smaller distal preapical tooth or denticle; distal preapical is weakest on the left mandible. Antenna with 4 segments.

4 schuetzi-complex (schuetzi). Right and left mandible each with one spiniform preapical tooth, without preapical denticles more distally. Antenna with 4 segments.