Key to Myopias of Borneo

This worker key is based on: [[Media:Jaitrong, W., Wiwatwitaya, D. et al. 2020. Three new species of the ant genus Myopias from Borneo (10.26107@RBZ-2020-0076 ).pdf|Jaitrong, W., Wiwatwitaya, D., Yamane, S. 2020. Three new species of the ant genus Myopias Roger, 1861 (Hymenoptera: Formicidae: Ponerinae) from Borneo. Raffles Bulletin of Zoology 68: 608–618]].

Jaitrong et al. stated the following regarding characters used for identifying Myopias species: Mandibular dentition, the shape of the median clypeal lobe, the shape of the subpetiolar process, and the size of the eye are among the important characters used to distinguish the species group of the genus found in Borneo. These morphological characters were used by several authors who provided keys to species of the genus also in other areas (Xu et al., 2014: Key to Oriental Myopias species; Probst et al., 2015: Key to Myopias workers ; Jaitrong et al., 2018). The Bornean species can be divided into three species groups by the morphological characters mentioned above. The first group (M. maligna) is characterised by 1) masticatory margin of mandible with 7–8 teeth; 2) median clypeal lobe long and broad, its anterior margin almost straight; 3) subpetiolar process subrectangular, with its ventral margin concave; 4) eye relatively large (more than 10 ommatidia along longest axis). The second group (M. modiglianii) is characterized by 1) masticatory margin of mandible with five teeth; 2) median clypeal lobe short, its anterior margin convex; 3) subpetiolar process subrectangular, with its ventral margin concave; 4) eye relatively large (more than 10 ommatidia along longest axis). The third group (M. breviloba, M. darioi, M. etsukoae, M. striaticeps, and M. suwannaphaki) is separated from the former two groups by 1) masticatory margin of mandible with 4–5 teeth; 2) median clypeal lobe long, its anterior margin concave or straight; 3) subpetiolar process subtriagular; 4) eye absent or very small (0–6 ommatidia along longest axis). The genus is clearly monomorphic in the worker caste with a small size variation occurring within species. Thus, the body size can be a good indicator in separating apparently similar species, for example M. maligna (6.50–8.00 mm in total body length) from M. modiglianii (11.40–11.50 mm in total body length). The sculpturing and colour are also important for species identification.

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1

 * Subpetiolar process not triangular, usually complex in shape, with anteroventral corner bearing a ventrally pointed tooth, posteroventral corner bearing a posteriorly pointed tooth. Seen from dorsolateral view, masticatory margin of mandible with more than 4 teeth. Eye relatively large, with more than 10 ommatidia along longest axis . . . . . 2


 * Subpetiolar process subtriangular, located anteroventrally, its apex truncate and pointed downward. Seen from dorsolateral view, masticatory margin of mandible with 3–4 teeth (subapical tooth often very difficult to see). Eye reduced, with 0–6 ommatidia along longest axis . . . . . 3

2

 * Seen from dorsolateral view, masticatory margin of mandible with 7–8 teeth. With head in full-face view, posterolateral corner bluntly angulate. Anterior margin of median clypeal lobe almost straight. Larger species (TL 11.40–11.50 mm; HW 1.85–1.90 mm) . . . . . . Myopias maligna


 * Seen from dorsolateral view, masticatory margin of mandibles with 5 teeth. With head in full-face view, posterolateral corners roundly convex. Anterior margin of median clypeal lobe convex. Smaller species (TL ˂ 8.00 mm; HW ˂ 1.50 mm) . . . . . . Myopias modiglianii

3

 * Dorsum of head with dense fine striation . . . . . . Myopias striaticeps


 * Dorsum of head without fine striation . . . . . 4

4

 * Anterior margin of median clypeal lobe concave . . . . . 5


 * Anterior margin of median clypeal lobe straight or weakly convex . . . . . 6

5

 * Anterior margin of median clypeal lobe extensively concave, its median portion with minute tooth (denticle). Lateral face of petiole irregularly striate. In dorsal view, petiole almost as long as broad . . . . . . Myopias etsukoae


 * Anterior margin of median clypeal lobe weakly concave without minute tooth at median portion. Lateral face of petiole smooth and shiny. In dorsal view, petiole slightly longer than broad . . . . . . . Myopias breviloba

6

 * Median clypeal lobe almost as long as broad or slightly shorter than broad. With mesosoma in dorsal view, metanotal groove distinct . . . . . . Myopias darioi


 * Median clypeal lobe narrow, clearly longer than broad. In dorsal view, petiole slightly broader than long. With mesosoma in dorsal view, metanotal groove indistinct or almost absent . . . . . . Myopias suwannaphaki