Aptinoma Fisher, 2009

Yoshimura, Masashi & Fisher, Brian L., 2011, A revision of male ants of the Malagasy region (Hymenoptera: Formicidae): Key to genera of the subfamily Dolichoderinae, Zootaxa 2794, pp. 1-34 : 9-10

Aptinoma Fisher, 2009

( Figs 2, 7, 11, 16, 17, 24, 30, 35, 42, 50, 56, 62, 67, 72, 77)

With characters of Dolichoderinae . All known males alate. Median hypostoma present ( Fig. 62). Mandible triangular, but its basal angle indistinct. Basal and masticatory margins of mandible wholly covered with many serrate denticles ( Fig. 72). Apical tooth on masticatory margin longer than subapical one. Palpal formula 6,3 (one specimen of A. mangabe dissected: Fig. 77). Third maxillary palpal segment nearly as long as fourth. Labrum not bilobed, with single distal apex and concavity on its distal margin absent ( Fig. 67). Antennal scape excluding its basal condyle shorter than length of flagellar segments 1 + 2 ( Fig. 2). Pedicel conical. First and second flagellar segments straight. Axillae on mesonotum medially compressed, anterior and posterior margins not parallel. Petiolar node raised vertically, its anterior margin nearly as long as the posterior margin in lateral view ( Fig. 7). Node not much expanded laterally. Petiole narrowly attached to abdominal segment III. Anterior surface of abdominal segment III with indentation that fits posterior surface of petiolar node. Pygostyles present.

Distal portion of abdominal sternum IX broadly spatulate ( Fig. 24). Apicoventral portion of basimere with spine-like projection ( Fig. 30). Harpago moderate in size, and widely separated from basimere by membranous region ( Figs 30, 35). Harpago narrow in ventral view, without a distinct ventral face (as in Fig. 23). Basal portion of aedeagus without any distinct ventral lobe ( Fig. 42). Ventral margin of aedeagus with denticles.

Forewing not extremely elongate apical to wing stigma, its radial sector reaches costal margin, media and 2 rsm recognizable apical to Rs+M, and 1 m-cu present ( Fig. 50). On hindwing, M+Cu, free sections of radial sector and cubitus almost vestigial, and cu-a weak but still present ( Fig. 56).

Remarks. Genus Aptinoma is endemic to Madagascar and only males of Aptinoma mangabe are presently known. Fisher (2009) proposed the combination of a shorter scape compared with flagellomeres 1 + 2, a palpal formula of 6,3, and a raised petiolar node as a diagnostic set of characters for Aptinoma in the Malagasy region. Here we propose a character unique to Aptinoma that consistently separates this genus from the other genera and provide additional characters to separate Aptinoma from the other Malagasy dolichoderine genera.

Males of Aptinoma are distinguished easily from other Malagasy dolichoderine genera by an abdominal sternum IX which is distally broadly spatulate ( Fig. 24). This character is so far globally unique to Aptinoma . In the Malagasy region, Technomyrmex and Tapinoma are superficially the most similar to Aptinoma . Aptinoma and Technomyrmex share the following unique characters: basal margin of the mandible wholly covered with serrate denticles and the concavity on the distal margin of the labrum reduced ( Figs 72, 76). Aptinoma and Tapinoma share a unique projection on the apicoventral portion of the basimere ( Figs 29, 30). The petiolar node in Aptinoma rises almost vertically, although the sternum is thickened posteriorly and the whole shape of the petiole seems to decline anteriorly ( Figs 7, 17). Therefore, the petiolar node in Aptinoma is best described as vertical, not as declining anteriorly as described in Fisher (2009).

The phylogenetic analysis of Ward et al. (2010) gives the intra-tribal relationship of Tapinomini as ((( Aptinoma + Tapinoma ) + Liometopum Mayr ) + ( Axinidris Weber + Technomyrmex )). They propose two hypotheses for the evolution of the “highly reduced petiole” seen in Aptinoma , Tapinoma , and Technomyrmex . The question is whether the petiole evolved once at the root of Tapinomini or at least twice at the roots of ( Aptinoma + Tapinoma ) and Technomyrmex independently. If we limit the discussion to males, the present result, a vertical petiolar node in Aptinoma , supports the theory that an anteriorly-declined and reduced petiolar node evolved independently in Tapinoma and Technomyrmex , and that there has been no reversal in Aptinoma , Axinidris , and Liometopum .

Additional discussion of characters is included in the remarks for Ochetellus .