Aptinoma, Fisher, B. L., 2009

Fisher, B. L., 2009, Two new dolichoderine ant genera from Madagascar: Aptinoma gen. n. and Ravavy gen. n. (Hymenoptera: Formicidae)., Zootaxa 2118, pp. 37-52 : 38-39

Aptinoma Fisher gen. n.

Figures 1-5, 7a

Type-species: Aptinoma mangabe sp. n., by present designation.

Diagnosis of worker. Dimorphic, with distinct minor and major workers. Major workers polymorphic. Lateral and anterior corner of hypostoma reduced to a thin sclerite, without expanded flange. Mandible with 4 -6 teeth apically on masticatory margin; counting from the apex, third tooth smaller than fourth, fifth smaller than sixth. Teeth followed by a fine series of 4-8 denticles (effaced in some major workers); basal angle blunt, with a relatively uninterrupted curve between the masticatory and basal margins; basal margin with minute serrations. Antennae with 12 segments. Palpal formula 6:3 (confirmed with dissection of A. mangabe ). Fourth maxillary palp segment subequal in length to segment 5. Fifth maxillary palp segment at the apical extreme of segment 4. Metanotal groove impressed but often weak. Propodeum unarmed, without any acute angle. Propodeal declivity almost straight in profile. Petiolar scale present, in the form of a node with low standing forward face. Gaster with only four plates on upper surface; fifth tergite (abdominal tergite 7) reflexed ventrally, and visible in ventral view where it forms a transverse plate abutting the fifth sternite. Mesosoma lacking erect hairs.

Diagnosis of queen. Based on one specimen of A. mangabe . Ergatoid with diagnostic characters of workers. Ocelli present. Scutellum distinct. Petiolar scale present, in the form of a node with a low standing forward face.

Diagnosis of male. Based on A. mangabe . Scape not reaching or surpassing posterior lateral margin of head in full-face view; scape length shorter than the length of segments 3 + 4. Second antenatal segment (pedicle) cone-shaped. Compound eyes relatively anterior on head. Anterior clypeal margin with a broad, shallow concavity. Posterior clypeal margin between the anterior and posterior surfaces of the antennal condyle. Palpal formula 6:3 (not confirmed with dissection). Mandible with single apical tooth followed by series of serrate teeth or denticles (> 20) along masticatory margin; basal angle of mandible indistinct, with a relatively uninterrupted curve between the two margins. Petiole with distinct scale, angled dorsally and strongly inclined anteriorly, with anterior face shorter than posterior face. First gastral segment in dorsal view with a groove for reception of entire height of petiole.

Discussion of characters. In many respects Aptinoma workers are similar to Tapinoma workers. Both genera share a number of traits, including the shape of the clypeus, position of eyes, and shape and number of mandibular teeth and denticles. Aptinoma differs from Tapinoma in palpal formula (6:3 in Aptinoma , 6:4 in Tapinoma (confirmed with dissection; Fig. 7c). Aptinoma also differs in having a more developed petiole node. The petiolar node in Tapinoma is flat, with almost no visible rise in the anterior face. In Aptinoma , a visible face is present. The face is more pronounced in major workers. The combination of palpal formula and form of petiolar node form an inclusive diagnosis that isolates Aptinoma from all other genera within the subfamily. Within the Malagasy region, the presence of dimorphic workers (with majors and minors), distinguish Aptinoma from all other dolichoderine genera. In males, the length of scape (shorter than the length of antennal segments 3 + 4), the presence of a petiole scale, and palpal formula 6:3 form an inclusive diagnosis.

Key to workers of Malagasy Aptinoma

1 In profile, metanotal groove distinct and set in shallow V-shaped impression (Figs 1a, e). Propodeal dorsum more or less convex, meeting steeply sloped declivity in blunt, narrowly rounded curve. In dorsal view, lateral margin of pronotum evenly convex, without blunt angle at widest point (Figs 1c, 2c). Body light to dark brown............................. ......................................................................................................................................................... Aptinoma antongil

- In profile, metanotal groove not set in a V-shaped impression (Figs 3a, 4a). Propodeum in absolute profile without differentiated dorsal and declivitous surfaces, forming single evenly rounded surface. In dorsal view, lateral margin of pronotum with blunt angle at widest point (Figs 3 c, g). Body yellow to orange....................................................... ........................................................................................................................................................ Aptinoma mangabe