Peronomyrmex greavesi, Shattuck, 2006

Shattuck, Steven O, 2006, A third species in the rare Australian ant genus Peronomyrmex Viehmeyer (Hymenoptera: Formicidae), Zootaxa 1194, pp. 49-55 : 53-54

Peronomyrmex greavesi sp. n. ( Figs 5–7 )

Types. Holotype worker, Clohesy River, near Mareeba , Queensland, 15 June 1937, T. Greaves (Australian National Insect Collection).

Diagnosis. This species can be separated from others in this genus by the absence of distinct sculpturing on the dorsum of the head, the broadly concave posterior face of the postpetiole and in having the area between humeral angles flat. This is also the northernmost species known in this genus.

Description. Total length 3.4 mm; maximum head length 0.81 mm; maximum head width (behind eyes) 0.73 mm; maximum diameter of eye 0.20 mm; scape length 0.60 mm; cephalic index (HW/HLx100) 90; scape index (SL/HWx100) 82; width across pronotal humeri 0.55 mm; Weber’s length of mesosoma 1.07 mm; dorsal petiole width 0.19 mm; maximum petiole height 0.36 mm; dorsal postpetiole width 0.21 mm; maximum postpetiole height 0.28 mm. Head capsule ( Fig. 5 ) shiny, with a very fine network of microsculpture. Dorsal surface of mesosoma ( Fig. 6 ) with weak longitudinal rugae which are more abundant laterally, absent centrally, underlying surface with indistinct, irregular weakly formed punctations. Lateral regions of mesosoma similar to dorsal surface but with longitudinal rugae shorter and less well defined. Petiole and postpetiole with smooth and weakly sculptured areas. Gaster smooth, shiny and with microreticulate sculpturing. Entire body covered with suberect, bluntly pointed hairs (those on gaster narrowly pointed rather than blunt). Colour chestnut­brown, dorsal areas slightly darker, lateral areas slightly lighter.

Comments. This species is known from a single specimen collected in 1937 by Tom Greaves. Despite extensive collecting in the area since this species has yet to be found again. As with other species in this genus, this is likely caused by its arboreal and nocturnal habits.

Conclusion

Peronomyrmex is now known from three species which are widely distributed along the east coast of Australia. The little biological information available suggests they are nocturnal and arboreal. These habits at least partially explain their infrequent collection. It seems unlikely the species described here will be the last in the genus. With three taxa known from only four collecting events it is clear that we are a long way from understanding these curious ants. We know nothing of their nesting habits and little about other aspects of their biology. It is unclear whether their infrequent encounter is caused by true rarity or by cryptic habits, or (more likely) a combination of these factors. Only further field work will answer these questions.

Figures

FIGURES 5, 6. Holotype worker of Peronomyrmex greavesi. Fig.5, head; Fig. 6, lateral view.

FIGURE 7. Distribution of specimens examined during this study.