Pristomyrmex trispinosus

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Pristomyrmex trispinosus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Pristomyrmex
Species: P. trispinosus
Binomial name
Pristomyrmex trispinosus
(Donisthorpe, 1946)

Pristomyrmex trispinosus casent0103301 profile 1.jpg

Pristomyrmex trispinosus casent0103301 dorsal 1.jpg

Specimen labels

A nest of P, trispinosus was found under a flat stone, and about 30 to 40 workers, two males, larvae, and pupae were collected; this species, when disturbed, simulates death (Donisthorpe, 1946).

Identification

Wang (2003) - Worker. Pronotum, mesonotum, and propodeum each with a pair of strong prominences; dorsal surfaces of head and alitrunk with dense regular striations; propodeal spines in dorsal view divergent; HW and HL > 1.10.

Pristomyrmex trispinosus is known only from Mauritius. It differs from Pristomyrmex bispinosus in the workers in having regular coarse striations on the entire dorsal surfaces of the head and the alitrunk and a pair of strong, digitlike prominences on the mesonotum. The workers of P. trispinosus and P. bispinosus are separable from those of Pristomyrmex browni by the following characters: P. trispinosus and P. bispinosus - Propodeal spines in dorsal view divergent, not laterally compressed; in profile rather straight. A relatively short diastema present between the preapical and the third tooth on the masticatory margin of the mandible. Larger species with HW > 1.08, HL > 1.14, SL > 1.32, PW > 0.68, TL > 4.36. P. browni - Propodeal spines in dorsal view subparallel, somewhat late rally compressed; in profile, bent at about a right-angle near the base. A relatively long diastema present between the preapical and the third tooth on the masticatory margin of the mandible. Smaller species with HW 0.82-0.90, HL 0.88-1.01, SL 0.80-0.97, PW 0.40-0.50, TL 3.24-3.78.

A member of the Trispinosus species group

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Malagasy Region: Mauritius (type locality).

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

Queens have yet to be collected.

Worker

Male

Nomenclature

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

  • trispinosus. Dodous trispinosus Donisthorpe, 1946f: 145, figs. 1-4 (w.m.) MAURITIUS. Combination in Pristomyrmex: Brown, 1971a: 3. See also: Wang, M. 2003: 489.

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

Description

Worker

Wang (2003) - TL 4.50-4.68, HL 1.16-1.22, HW 1.11-1.18, CI 91-97, SL 1.33-1.44, SI 117-122, EL 0.20-0.24, PW 0.66-0.70, AL 1.16-1.26, PPW 0.27-0.30, PPL 0.24-0.26, PPI 108-11.5 (n = 6).

Mandibles smooth and shining. Masticatory margin of mandible with four teeth arranged as the strongest apical + the second strongest preapical + a short diastema (sometimes, this diastema is not distinct) + a small denticle + a long diastema + a small basal denticle. Basal margin of mandible lacking a toothlike prominence. Anterior margin of the median portion of clypeus with at least five denticles, but sometimes two lateral denticles are fused into a broad lobe. Two ends of the anterior clypeal margin each with a developed prominence. Ventral surface of clypeus lacking toothlike prominences. Clypeus usually with a few longitudinal rugae. Palp formula 1,2. Frontal calinae absent. Antennal scrobes absent. Frontal lobes absent so that the antennal articulations are completely exposed. Antennal scapes long, when lying on the dorsal head surpassing the occipital margin by one-fourth to one-third of their length. Eyes usually containing 11 to 12 ommatidia in the longest row. Occipital margin in full-face view slightly concave. Alitrunk in profile with a convex pro-mesonotum and a deeply concave propodeal dorsum. Pronotum armed with a pair of moderately long acute spines. Mesonotum with a pair of thick, blunt, digitlike short prominences. Propodeum with a pair of developed long spines that, in dorsal view, are joined together at the base but divergent along their length so that they form a fork. Metapleural lobes dentiform. Petiole node in profile nodifonn with a long anterior peduncle. Postpetiole in profile rounded anterodorsally but usually with a distinct posterodorsal angle; in dorsal view, postpetiole slightly broader than long. Entire dorsum of head with regular coarse striations: many striations spread out from the center to the two sides and to the occipital margin; some are around the antennal fossae, the rest are some longitudinal rugae present on the sides of the head. Sides and the dorsum of alitrunk with numerous evenly distributed, circular coarse striations. Center of mesonotum with a few coarse short rugae . Petiole and postpetiole rather smooth and shining, but sometimes their sides with a few superficial short rugae. Gaster un sculptured. All dorsal surfaces with numerous erect or suberect hairs. Scapes and tibiae with numerous erect or suberect short hairs. A row of forward-projecting hairs present near the anterior clypeal margin. Color yellow-brown, but sometimes reddish-brown.

Male

Wang (2003) - One syntype male (BMNH), together with a number of syntype workers, constitutes a series (see Donisthorpe, 1946): TL 4.46, HL 0.72, HW 0.70, CI 97, SL 0.20, SI 29, EL 0.22, PW 0.90, AL 1.42 (n = 10.

Head, including the eyes, broader than long. Clypeus somewhat transverse, convex in middle. On the mesoscutum, notauli indistinct. Scuto-scutellar sulcus wide, separated into small cells by narrow ridges. Propodeum weakly tuberculate, lacking teeth or spines. Metapleural lobes subtriangular. Petiole node in profile low with a fairly long anterior peduncle. Postpetiole in profile rounded dorsally. Dorsum of head smooth and shining. Mesoscutum smooth and shining, but mesoscutellum with some rugae and a few foveolate punctures. Petiole node rather smooth. Postpetiole and gaster unsculptured, smooth, and shining. All dorsal surfaces with abundant erect or suberect long hairs. Scapes and tibiae with numerous erect or suberect short hairs. Color reddish-brown; wings somewhat dusky.

Type Material

Wang (2003) - Syntype workers and males, Mauritius: Cocotte Mt., 27.xii.1941 and 6.ii.l943 (R. Mamet) (The Natural History Museum, Los Angeles County Museum of Natural History, Museum of Comparative Zoology) [examined].

References

  • Brown, W. L., Jr. 1971a. Characters and synonymies among the genera of ants. Part IV. Some genera of subfamily Myrmicinae (Hymenoptera: Formicidae). Breviora 365: 1-5 (page 3, Combination in Pristomyrmex)
  • Donisthorpe, H. 1946j. A new genus and species of Formicidae (Hym.) from Mauritius. Proc. R. Entomol. Soc. Lond. Ser. B 15: 145-147 (page 145, figs. 1-4 worker, male described)
  • Wang, M. 2003. A Monographic Revision of the Ant Genus Pristomyrmex (Hymenoptera:Formicidae). Bull. Mus. Comp. Zool. 157(6): 383-542 (page 488, figs. 199-200 worker, male described)