Polyrhachis dives species-group

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The species in this group is a member of the subgenus Myrmhopla.

Species

Overview

The Polyrhachis dives species-group was originally delimited by Emery (1925) and has previously contained as many as 77 species and subspecies. Dorow (1995) redefined the group and transferred a number of species into the earlier established armata-, sexspinosa- and viehmeyeri-groups (all Emery, 1925), or into his newly proposed arachne-, bicolor-, cephalotes-, hector- and mucronata-groups. The P. dives-group, as presently defined, includes about 14 species and subspecies with only one Australian species, P. dives .

(see the subgenus page for more information about the species groups referenced above)

Diagnosis

Worker

(modified from Dorow, 1995) Mostly medium-sized ants (HL 1.40-2.00), some species exhibiting slight polymorphism. Mandibles rather densely longitudinally striate or rugose with numerous piliferous pits. Anterior clypeal margin with central, medially emarginate flange, laterally flanked by acute teeth. Head semicircular in side view, almost circular in frontal view. Genae immarginate or with a short carina running about half way from occipital margin towards mandibular bases (as in some extralimital species, e.g. Polyrhachis lacteipennis). Eyes rather flat or only moderately convex, in full face view not or only marginally exceeding lateral cephalic outline. Mesosoma totally immarginate. Pronotum armed with rather short or only moderately long spines (except in P. dives belli, where pronotal spines are slender and relatively long); propodeal spines slender and elevated with their tips curved outwards. Petiole with lateral spines, that in most species conform to shape of gaster, and a pair of distinct intercalary teeth. Body rather distinctly, more-or-less regularly, reticulate-punctate (as in P. dives), moderately rugose (as in P. lacteipennis) or coarsely foveolate (as in Polyrhachis menelas). Gaster shagreened or closely punctate. Body with only a few, short, erect hairs; closely appressed, mostly silvery or pale golden pubescence rather sparse over head and body (as in P. dives) or virtually lacking (as in P. lacteipennis). Gaster with somewhat longer, silvery or golden pubescence, that is virtually lacking in several extralimital species. Body and appendages mostly black with gaster black or very dark reddish-brown.

A nest of P. dives.

Queen

Queen in several species (e.g. P. dives) distinctly larger than worker with usual characters identifying full sexuality, including three ocelli, complete thoracic structure and wings. Spines distinctly shorter with pronotal spines reduced to acute angles. Propodeal spines modified into blunt, horizontal, posteriorly directed and somewhat dorso-ventrally compressed stubs; petiolar spines very short, only weakly curved, almost straight. Body sculpturation, pilosity and colour identical to that in worker.

Distribution and biology

The Polyrhachis dives species-group is the most widespread species-group within Myrmhopla. It stretches from Guam Island in the Pacific, throughout east and south-east Asia (e.g. China, Japan, Taiwan, Philippines, Malaysia, Thailand, Myanmar, Nepal, India, Sri Lanka), the Middle East and Arabian Peninsula (e.g. Pakistan, Iran, Iraq, Israel, Saudi Arabia, Oman, Yemen) and reaches as far west as Morocco in northern Africa. From southern Asia it extends southwards to Indonesia, New Guinea and northern Australia. Members of this group are mostly arboreal, building nests upon the leaves and branches of trees and shrubs, preferably in open habitats, such as grassy woodlands, open forests and swamps (see image). However, some extralimital species (e.g. P. lacteipennis) were observed to be lignicolous or subterranean nesters. The incorporation of silk and occasionally carton occurs in all arboreal nests. These nests can be either mono- or polydomous. Single and multiple queen colonies have been documented in P. dives (see Robson & Kohout, 2007).

Related Pages

References