Apterostigma eowilsoni, Schultz, T. R., 2007

Schultz, T. R., 2007, The fungus-growing ant genus Apterostigma in Dominican amber., Advances in ant systematics (Hymenoptera: Formicidae): Homage to E. O. Wilson - 50 years of contributions. (Memoirs of the American Entomological Institute 80), pp. 425-436 : 427-432

Apterostigma eowilsoni , new species

(Figures 3, 4, and 5)

HOLOTYPE (worker): AMBER: Oligo-Miocene; Dominican Republic; AMNH no. DR- 16 - 292; no other locality data. USNM SIANT database specimen reference number 00443150 . Deposited in AMNH .

Measurements: head length = 0.99 mm; head width (not including eyes) = 0.68 mm; scape length = 0.99 mm; Weber ’ s length = 1.44 mm; metafemur length = 1.37 mm.

DESCRIPTION: In full-face view, head bluntly angled at posterolateral corners and again at vertexal carinae, and slightly indented medially. Occipital “ collar ” short and not expanded posteriorly; collar integument with a series of longitudinal rugae. Frontal carinae strongly produced, extending posterad past the level of the eyes. Vertexal carinae strong, preocular carinae weak. Frontal lobes evenly rounded. Antennae with the typical attine number of eleven segments, the apical segment 2.25 × as long as the subapical segment, the subapical segment two-thirds the length of the pedicel. Clypeal border broadly convex, and, as far as can be seen, with only an exceedingly thin strip of cuticle, forming the anterior edge of the clypeus, smooth and of a darker color than the rest of the clypeal integument, the rest identical to the integument of the rest of the head. Mandibles apparently with eleven sharp teeth, the teeth arranged in a curious pattern heretofore unencountered in the genus: reckoning from the apex, the sixth and eighth teeth on the left mandible and the fourth and seventh teeth on the right mandible distinctly larger than the rest; the smaller teeth in between of various sizes, not decreasing in size toward the mandibular base. Lateral corners of the hypostoma produced into blunt, rounded hypostomal teeth. In frontal view the eyes typical, in lateral view the eyes half-hemispheres truncated from behind by integument, but in dorsal view the eyes forward-directed subconical hemispheres mounted on lobes or tubercles that project, perpendicular and earlike, from the sides of the head. As far as can be determined given the complications of observing through the amber matrix, eye width approximately nine ommatidia across the transverse circumference and approximately twelve ommatidia across the longitudinal circumference.

Promesonotum with a pair of strong longitudinal carinae, in lateral view the carinae ending anteriorly in an abrupt vertical wall above the promesonotal junction. Anterolateral mesonotal carinae strong and humeral prominences apparently absent. Posterior mesonotum (“ metanoto ” of Lattke, 1997) without sculpture. Ventral mesopleural carina present and complete, but not lamellate. Meso- and metacoxae of typical form, without lamellate or keel-like carinae. Propodeum carinate on the basal face, weakly carinate on the declivous face, and lacking propodeal spines. Propodeal shoulder evenly rounded, the propodeal spiracles directed posterad and mounted on tubercles. Ventral surfaces of the mesopleura covered with six small spherical objects, apparently clusters of minute bubbles.

Petiole with an elongate peduncle bearing an anterior ventral tooth and a low but distinct node. What appears to be a second, posterior ventral tooth is actually debris in the amber matrix. Viewed dorsally, the postpetiole approximately 1.3 X broader than long, subtriangular in shape, and about half as broad anteriorly than posteriorly. Entire length of the first gastral (fourth abdominal) tergite strongly laterally carinate. Body covered with long, fine, simple, erect setae with a maximum length of 0.15 mm.

By Lattke ’ s (1997) primary criterion of the presence of a smooth and shining clypeal border, A. eowilsoni belongs to the pilosum group. The anterior clypeal border in this species is, however, extremely reduced and thus represents a credible intermediate in the morphocline spanning the typical (and presumably plesiomorphic; Lattke, 1999) state in the pilosum group and the derived state (clypeal border absent) in the auriculatum group. Of the species known to me, the reduced clypeal border in A. eowilsoni most resembles that of an undescribed Costa Rican species that keys out to the unrevised “ pilosum complex ” of species in Lattke ’ s (1997) key. Certainly the most striking character of A. eowilsoni is the remarkably protruding eyes, which are similar in form to — but far more developed than — the eyes found in the auriculatumgroup species A. pariense (Venezuela and Bolivia; specimens examined) and A. reburrum (Colombia; specimens not seen), which also have their eyes mounted on markedly protruding tubercles. Apterostigma eowilsoni clearly possessed excellent stereoscopic forward vision, limited lateral vision, and no rearward vision.

ETYMOLOGY: It gives me great pleasure to name this striking and possibly phylogenetically important fossil fungus-growing ant after E. O. Wilson, in celebration of his long career of myrmecological discovery.