Rasopone Species-Level Characters

Longino, John T. & Branstetter, Michael G., 2020, Phylogenomic Species Delimitation, Taxonomy, and ‘ Bird Guide’ Identification for the Neotropical Ant Genus Rasopone (Hymenoptera: Formicidae), Insect Systematics and Diversity 4 (2), No. 1, pp. 1-33 : 9

Rasopone Species-Level Characters

The species of Rasopone have a uniform habitus ( Fig. 1A ). Worker HW varies from 0.80 to 1.70. The coefficient of variation for metric characters is typically ~5%. The medial projection of the anterior clypeal margin varies from strongly square-cut, flat medially and with sharp lateral corners ( Fig. 1E ), to medially emarginate with rounded lateral lobes ( Fig. 1F ). These two states are referred to as truncate or sinuous in species accounts. The mandibles vary from striate to smooth and shining. The sides of the head show variable levels of pilosity, from bare to having numerous short setae uniformly distributed. Face sculpture is usually a uniform surface of dense minute puncta, but in some species these are overlain with larger, more widely spaced puncta. When present, the larger puncta are usually faint and only visible under particular orientation and lighting. The degree of expression of these larger puncta is a continuum across species, and their presence is only noted for species with relatively strong expression. The petiole in lateral view varies from scale-like to cuboidal. The anterior margin is always flat to slightly concave. In species with strongly cuboidal nodes the posterior margin is also flat, parallel to the anterior margin, and there is a differentiated dorsal face ( Fig. 1D ). In species with a scale-like node, the dorsal and posterior faces are not differentiated and form a single convex curve ( Fig. 1B ). Among species there is a continuum from cuboidal to scale-like nodes ( Fig. 1 B–D). Petiolar nodes also vary in height to length ratio, some being relatively tall and thin, others shorter and longer.

Queens are very similar to workers except for larger compound eyes, presence of ocelli, and queen-typical mesosomal sclerites ( Fig. 4 ). The ocelli are always very small. In species for which queens and workers are known, HW is approximately the same for the two castes. Rasopone cubitalis may be an exception, with queens ~1.17× larger than workers.

Males are known for a few species. The type series of R. rupinicola was collected with one or more males. Males occur in Malaise samples and a few have been associated with workers using COI sequence data. A figure is provided of the associated male of R. mesoamericana sp. nov. ( Fig. 5 ), and several males are figured in Supp Figs. S18, S21, and S31 (online only), but otherwise males are not examined in this study.

Figures

Fig. 1. Characteristics of Rasopone species. (A) Habitus. (B) Scale-like petiole, showing definitions of petiole height (PTH) and petiole length (PTL), and the distinctive shape of the sternite. (C) Petiolar node intermediate between scale-like and cuboidal. (D) Cuboidal petiolar node. (E) Anterior clypeal margin truncate, with angulate lateral lobes. (F) Anterior clypeal margin sinuous, with rounded lateral lobes.

Fig. 4. Dealate queen of Rasopone ferruginea (Nicaragua, CASENT0624181). Scale bars are 0.5 mm for face view, 1.0 mm for dorsal and lateral views.

Fig. 5. Male of Rasopone mesoamericana sp. nov. (Nicaragua, CASENT0627722). Scale bars are 0.5 mm for face view, 1.0 mm for dorsal and lateral views.