Crematogaster rasoherinae

diagnosis

Diagnosis. Workers of Crematogaster rasoherinae can be distinguished from all other Malagasy Orthocrema by the presence of small anterolateral denticles on the petiole and the rectangular shape of the same. Queens are distinct from all other species by their rectangular petiole shape. In addition, the absence of propodeal spines distinguishes Crematogaster rasoherinae queens from Crematogaster madecassa and Crematogaster razana, whereas very small size (HW 0.80 - 0.89, WL 1.50 - 1.63) and large eyes (OI 0.30 - 0.34) easily separate them from Crematogaster volamena and Crematogaster mpanjono.

Taxonomy and species-groups of the subgenus Crematogaster (Orthocrema) in the Malagasy region (Hymenoptera, Formicidae)

discussion

Discussion. An intriguing characteristic of Crematogaster rasoherinae is the morphological variability of this species on the Comoros Islands compared to the remainder of its distribution range. In Madagascar, the Seychelles and Mayotte this species always possesses propodeal spines. On the Comoros Islands in contrast, propodeal spines can be present (as in Figure 24 B), reduced or entirely absent (as in Figure 24 E). More specifically, all specimens examined from the island of Grand Comore have no, or very reduced propodeal spines, whereas on Anjouan and Moheli propodeal spines are mostly reduced or absent and present only in fewer individuals. This spine-polymorphism was presumably the basis of the description of the here synonymized Crematogaster voeltzkowi. Anjouan is the type locality for this species name and the syntype specimens represent the morphological form lacking the propodeal spines. Analysis of DNA sequence data from both the nuclear markers (see Figure 1) and ancillary mitochondrial data however clearly shows a lack of genetic divergence between the ' armed' and ' unarmed' forms in Crematogaster rasoherinae. The cause and maintenance of this intraspecific polymorph

Taxonomy and species-groups of the subgenus Crematogaster (Orthocrema) in the Malagasy region (Hymenoptera, Formicidae)

distribution

Distribution and biology. Crematogaster rasoherinae is the most widespread species of the Malagasy Orthocrema, and in fact it is one of the most abundant Crematogaster species in Madagascar and on a number of Indian Ocean islands (Figures 26 D-F). The species is distributed throughout all native forest habitats in Madagascar - rainforest, dry or spiny forest alike - and is also found in disturbed habitats and urban areas. It has been collected at elevations up to 1225 m, but appears to be more common at lower elevations. In natural habitats this species is predominantly arboreal nesting, both in dead twigs as well as in live plant parts. However, ground nesting in rotten logs or branches does occur occasionally. Biologically Crematogaster rasoherinae is interesting because of the presence of intermediate workers (i. e., individuals intermediate between workers and queens) (Figures 25 A-E) of unknown function in the colony. I have found intermediates in all four colonies that I collected of this species, with the highest number hereby being eight individuals in one nest. In all cases a normal, dealate queen also was present in the nest. None of the intermediates observed was winged

Taxonomy and species-groups of the subgenus Crematogaster (Orthocrema) in the Malagasy region (Hymenoptera, Formicidae)