Diacamma sp.

Japanese Name

Toge-oohari-ari

Large ponerine ant. Total length of workers around 10 mm. Body color black, mandibles and legs reddish brown. Hairs sparse, erect, light brown. Distinctive paired spines on petiolar dorsum, directed posterodorsally. Head regularly longitudinally striate; trunk and petiole striate; anterior portion of 1st gastral segment with all striae in concentric arches pointing forwards; the rest of gaster smooth and shinning.

The male of this species is large, characterized by toothed tarsal claws and distinct median spines at the terminal end of the last gastral tergum. On Okinawa this species is found in limestone areas, nesting in the soil, tree cavities or spaces between rocks at forest margins (Fukumoto, 1983). Colonies comprise 20 to 400 workers. Nesting sites are frequently changed under unfavorable conditions (Fukumoto & Abe, 1983; Abe & Uezu, 1977). This species is found on several islands of the Nansei Archipelago, but its distribution is rather sporadic. Recent karyological studies of Diacamma show that there are many possible sibling species in tropical Asia (Imai et al., unpublished). Wilson (1958b) synonymized many names under D. rugosum Le Guillou, but this nomenclature needs reappraisal, since morphological features distinguishing species can be very subtle. The Japanese species has often been cited as D. rugosum or D. rugosum geometricum v. anceps. Its morphology is consistent with D. rugosum, in the broad sense proposed by Wilson, but its exact status nomenclature must await better understanding of the genus at large, including karyological analysis of all possible taxa.

Nansei Is (Amami-oshima I., Tokunoshima I., Kume I., Okinawa I.).