Pristomyrmex costatus

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Pristomyrmex costatus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Pristomyrmex
Species: P. costatus
Binomial name
Pristomyrmex costatus
Wang, M., 2003

Pristomyrmex costatus casent0901719 p 1 high.jpg

Pristomyrmex costatus casent0901719 d 1 high.jpg

Specimen Labels

Swamp forest, rainforest, nest ex rotten log, lowland rainforest, on rotten log and in leaf litter, primary forest, sifting under bark.

Identification

Wang (2003) - Worker. Ventral surface of clypeus lacking a developed tooth, but usually with a transverse ruga; pronotal spines fairly long, ca. 1.5 to 2 times the length of propodeal armaments, but distinctly shorter than the distance between the bases of two pronotal spines; dorsal surfaces of head and alitrunk sculptured with coarse rugoreticulum; petiole node lacking foveolate punctures; first gastral tergite lacking erect or suberect hairs.

Pristomyrmex costatus is extremely similar in appearance to another Oriental species, Pristomyrmex sulcatus. The workers and queens of the two species can be separated as follows: In P. costatus, the ventral surface of the clypeus lacks a toothlike prominence, usually with a transverse ruga; in P. sulcatus, the ventral center of the clypeus has an acutely prominent tooth and no transverse ruga. The separation of P. costatus from Pristomyrmex modestus and from Pristomyrmex bicolor is summarized under the latter names.

A member of the Quadridens species group

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Indo-Australian Region: Borneo, Indonesia, Malaysia (type locality), Philippines, Singapore.


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

The biology of most Pristomyrmex species is poorly known. From Wang (2003): Most species of Pristomyrmex dwell in the rainforest, foraging as predators or scavengers. An Asian species, Pristomyrmex punctatus, however, occurs in open and disturbed habitats (e.g., bare hills, agricultural areas, and beaches). These ants prefer to nest in soil, litter, or rotten wood; in rotten parts of living trees; in dead standing trees; or around plant roots.

Pristomyrmex is of great interest because it exhibits several unusual biological and evolutionary phenomena. The absence of morphologically normal queens and reproduction primarily by unmated workers in P. punctatus {=P. pungens) is a highly unusual life history in the Formicidae. Ergatoid queens, a special wingless female caste morphologically intermediate between the queen and the worker, are present in at least four species: Pristomyrmex punctatus, Pristomyrmex africanus, Pristomyrmex wheeleri, and Pristomyrmex mandibularis; two of them (P. africanus and P. wheeleri) possess both queen and ergatoid queen castes.

Simulating death, slowness of movement, and nocturnal foraging has been recorded in Pristomyrmex (Donisthorpe, 1946; Taylor, 1965; Weber, 1941). Colony size varies greatly among species, ranging from about a dozen to several thousand workers (Donisthorpe, 1946; Itow et al, 1984; Mann, 1919; Taylor, 1965, 1968).

Castes

Worker

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • costatus. Pristomyrmex costatus Wang, M. 2003: 434, figs. 123-126 (w.q.) WEST MALAYSIA.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Holotype. TL 4.14, HL 0.99, HW 0.96, CI 97, SL 0.96, SI 100, EL 0.21, PW 0.68, AL 1.12, PPW 0.30, PPL 0.30, PPI 100. Paratypes, 3 workers: TL 4.48-4.54, HL l.04-1.08, HW 0.98-1.02, C1 94-94, SL 1.07-l.12, SI 108-110, EL 0.20-0.20, PW 0.68-0.72, AL l.18-l.24, PPW 0.30- 0.31, PPL 0.33-0.34, PP1 91-94.

Mandibles usually with several longitudinal rugae. Masticatory margin of mandible with four teeth arranged as two adjacent strong apical teeth + a long diastema + two small basal teeth of similar size. Basal margin of mandible lacking a distinctly curved lobe or tooth. Clypeus with a strong median longitudinal carina. Anterior clypeal margin with a median denticle and two to three others on each side. Ventral surface of clypeus possessing or lacking a transverse ruga, never armed with a developed, acute tooth. Palp formula 1,3. Frontal carinae strong, extending to the level of the posterior margins of eyes. Slightly concave scrobal areas present lateral to the frontal carinae. Frontal lobes weak so that the antennal articulations are almost entirely exposed. Antennal scapes, when lying on the dorsal head, slightly surpassing the occipital margin of head. Eyes containing 9 to 10 ommatidia in the longest row. Pronotum armed with a pair of strong and fairly long spines that are ca. 0.19 to 0.27, 1.5 to 2 times the length of propodeal armaments, but distinctly shorter than the distance between the bases of two pronotal spines. Propodeum with a pair of acute short spines that are ca. 0.10 to 0.16 and more slender than the pronotal ones. Metapleural lobes subtriangular. Petiole node in profile, slightly higher than long, with a fairly long anterior peduncle; its anterodorsal angle is on a higher level than the posterodorsal. Postpetiole in profile rounded dorsally, in dorsal view broadening from front to back. Dorsum of head, except for the scrobal areas where there are only some transverse rugae, with well-developed coarse rugoreticulum. Similar sculpture present on the sides of pronotum and the dorsum of alitrunk. Petiole with a coarse longitudinal ruga on each side, but dorsum of petiole node unsculptured and smooth. Dorsum of postpetiole unsculptured and smooth. Gaster smooth and shining. Dorsal surfaces of head and alitrunk with numerous erect or suberect long hairs. Sides and dorsum of petiole node and postpetiole with five or more pairs of hairs in the type specimens. First gastral tergite lacking erect or suberect hairs. Several pairs of forward-projecting hairs present near the anterior clypeal margin. Scapes and tibiae with some erect to suberect hairs. Color reddish-brown.

Queen

Two queens, respectively, from N. Borneo and Sarawak, with the following measurements: TL 5.24, .5.26; HL 1.12, 1.20; HW l.16, l.22; CI 102, 104; SL 1.18, l.20; SI 98, 102; EL 0.28, 0.31; PW 1.00, 1.10; AL 1.44, 1.62; PP\V 0.38, 0.44, PPL 0.40, 0.44, PPI 95, 100.

General shape with normal caste differences from the worker, pronotum unarmed; other characters similar to worker.

Type Material

Holotype Worker. The Natural History Museum. Malaysia: Neg. Sembilan, Pasoh For. Res., xi. 1994, (M. Brendell, K. Jackson, and S. Lewis). Paratypes. Museum of Comparative Zoology. Three workers, N. Borneo (E. Mjoberg).

References

  • Wang, M. 2003. A Monographic Revision of the Ant Genus Pristomyrmex (Hymenoptera:Formicidae). Bull. Mus. Comp. Zool. 157(6): 383-542 (page 434, figs. 123-126 worker, queen described)