Polyrhachis militaris species-group

Every Ant Tells a Story - And Scientists Explain Their Stories Here
Jump to navigation Jump to search

The species in this group are members of the subgenus Myrma.

Species

Identification

Bolton (1973) - The group is characterised by the complete margination of the pronotum, mesonotum and in all but one species (Polyrhachis sulcata) the propodeum, and the markedly impressed metanotal groove. The margination of the alitrunk is interrupted at the sutures. The majority of species have an unmodified, arcuate clypeal margin and have retained the armament of the propodeum as a pair of upcurved teeth or spines, which in some species are reduced to mere tubercles, but only very rarely are they completely lost. Sculpturation in the group consists usually of a fine, superficial reticulation or a regular striation or striate-rugulation. Sculpturing of the form found in the viscosa group, of a fine dense reticulate-puncturation overlaid by a rugoreticulum is very rare, but numerous species have the gaster reticulate-punctate.

Within the group the species tend to polarise into one of three complexes, centring on Polyrhachis fissa, Polyrhachis concava and Polyrhachis militaris respectively. The species allied to jissa tend to be shorter, more stoutly built forms with a stronger sculpturation, usually of longitudinal striae or rugae. The pronotal spines tend to be short, flattened and broadly triangular in dorsal view whilst the petiolar armament shows all spines of approximately equal length or with the lateral pair developed at the expense of the dorsals. In the series jissa asomaningi decemdentataphidiascornuta there is a gradual reduction in the length of the dorsal pair of spines, and a gradual increase in the length and thickness of the laterals, until in Polyrhachis cornuta the dorsals are reduced to a pair of very short spines. This series appears to parallel the condition found in part of the viscosa group. All species closely related to jissa have numerous erect hairs on the dorsum of the head and alitrunk, but these may be absent from the appendages.

The species most closely related to concava tend to be more slender and elongate forms, of small to medium size and with a fine sculpturation. This is usually a superficial reticulation but in some is a fine and dense reticulate-puncturation. Erect hairs are usually only present on the anterior clypeal margin and the apex of the gaster, but in some species a single pair of hairs is present on the dorsum of the head. The petiole is always armed with a pair of long dorsal spines, sometimes very long and recurved over the base of the first gastral tergite, and a pair of smaller spines or teeth laterally.

The allies of militaris are large species, often 10 mm or more in total length. General build of the body varies but the majority are stocky, rather broad species. Sculpturation varies from striate to a very fine superficial reticulation, but all species are clothed with erect hairs on the head, appendages, gaster and at least part of the dorsal alitrunk. The petiole is armed with a pair of long dorsal spines and a shorter pair of lateral spines or teeth. In some species the laterals have been completely lost. The sequence latispinasulcatagagateswellmani shows the gradual reduction of the lateral spines to teeth and finally, in wellmani, their disappearance.

Notes

Bolton (1973) - Species of the militaris group are distributed throughout Africa, but those related to fissa and concava are mostly confined to forested regions. The group appears to be the basic stock, from which members of the remaining groups have developed by reduction of the characters listed above. The only exception to this assumption is the gamaii group which seems quite unrelated.

Related Pages

References