Asian Crematogaster ranavalonae group

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Based on: Hosoishi, S. 2015. Revision of the Crematogaster ranavalonae-group in Asia, with description of two new species (Hymenoptera, Formicidae). Journal of Hymenoptera Research 42, 63-92.

Key to species

Key to Asian Crematogaster ranavalonae group species

The Asian Crematogaster ranavalonae group

Members of the Crematogaster ranavalonae-group have been differentiated based on characters found in the worker and queen castes (Blaimer 2012a, 2012b). Although workers of the Asian members also posses the taxonomic characters identified by her, the propodeal spines in some of the Asian species are not well developed, appearing instead as small tubercles. However, I have identified a unique character among the members of the Asian C. ranavalonae-group; that is, while the ridge separating the lateral and ventral portions of the mesopleuron is distinct in most Crematogaster species, it is not distinct in the Asian members of the C. ranavalonae-group. Furthermore, the queen caste of some members of the species group has falcate mandibles, suggesting the occurrence of temporal social parasitism in those species (Forel 1910; Santschi 1934; Hölldobler and Wilson 1990; Blaimer 2012a). However, among the Asian fauna, falcate mandibles are found only in the queen of C. augusti and are unknown in other species due to the rarity with which they are encountered in the field. In this study, I do not treate the queen caste because it is not represented in my collections.

The Crematogaster ranavalonae-group consists of twenty-two species, including eleven species from Africa and Madagascar, ten from Asia, and one from New Guinea (Blaimer 2012b). Among the Asian fauna (ten species and four subspecies), four species and three subspecies have been described from India. It is considered that India is the center of diversity in this species-group, but this may be an overestimate attributable to the rarity of this species group in the field. This paper provides a revision of the Asian members of C. ranavalonae-group, based on the morphological characters of the worker caste.

Hosoishi 2015. Figure 7.

An important character in the Asian Crematogaster ranavalonae-group is the ventrolateral katepisternal ridge (Fig. 7). The ridge separates the mesopleuron lateral surface from ventral surface. Most Asian Crematogaster species have a well-defined ridge separating the two surfaces (Fig. 7B), but in some species the ridge is absent or vestigial (Fig. 7A). The ridge is visible in pinned specimens from lateral or ventrolateral view.

Asian Crematogaster ranavalonae-group description

The Asian members of the Crematogaster ranavalonae-group not only have the morphological features diagnosed by Blaimer (2012a, 2012b), but also show the additional features below.

(i) Pronotum steeply raised in lateral view.

(ii) Ventrolateral katepisternal ridge indistinct, but weakly developed anteriorly in some species.

(iii) Integument essentially smooth and shiny.

(iv) Erect pilosity almost absent. Some erect setae are developed on the clypeus or dorsal surface of petiole and postpetiole, but absent on the dorsum of head, mesosoma and fourth to seventh abdominal tergites.

(v) Dorsum of head, mesosoma and fourth abdominal tergite with short and appressed setae.

This species group is easily defined from other Asian Crematogaster in having a steeply raised pronotum, smooth and shiny body surface, and short and appressed body setae.