Pristomyrmex species groups

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The following species groups are based on: Wang, M. 2003. A Monographic Revision of the Ant Genus Pristomyrmex (Hymenoptera:Formicidae). Bull. Mus. Comp. Zool. 157(6): 383-542.

Cribrarius Group

South Africa and Mozambique.

Worker: Medium sized, with the following combination of characters.

(1) Masticatory margin of mandibles with a long diastema between the preapical and the basal tooth.

(2) Palp formula 4,3.

(3) Frontal carinae present.

(4) Lateral portions of clypeus reduced to a margin, and the antennal fossae reaching the anterior clypeal margin.

(5) Frontal lobes absent.

(6) Lamella that encircles the base of antennal scape, entire.

(7) Dorsum of alitrunk convex, not depressed; pro-mesonotal suture absent.

(8) Pronotum armed with a pair of strong, acute, short spines.

(9) Propodeal spines well developed and long; in dorsal view not forming a “fork”.

(10) Petiole node thick in profile; its anterodorsal, posterodorsal, and posteroventral corners showing right angles approximately.

Levigatus Group

This is a monophyletic group, containing 12 species. They are endemic in the Oriental region, except for one species (P. minusculus) entering in North Queensland, Australia. Further, most of the species of this group occur in Papua New Guinea and some nearby islands.

An ergatoid queen easte has been found in P. mandibularis of the group. This caste is also present in the punctatus and quadridens groups. Pronotal armaments, widely occurring in the cribrarius, quadridens, and trispinosus groups, appear in the workers of one species (P. minusculus) of the levigatus group. These facts indicate that ergatoid queens and pronotal armaments have arisen several times in Pristomyrmex, respectively.

Worker. This group shows the following combination of characters:

(1) Usually smal1-sized species: HW: 0.60-0.96 in 11 species, 0.98-1.26 in one species (P. lucidus). HL: 0.60- 0.90 in 11 species, 0.92-1.16 in P. lucidus. TL: 2.20-3.49 in 11 species, 3.71-4.84 in P. lucidus.

(2) Masticatory margin of mandible with four teeth arranged as the strongest apical + the second strongest preapical + the smallest third + an acute basal tooth that is larger than the third tooth but smaller than the apical and preapical teeth; masticatory margin lacking a distinct diastema.

(3) A tooth that is short and broad or prominent, present about midway on the basal margin of mandible.

(4) Lateral portions of clypeus in front of antennal insertions reduced to a narrow margin.

(5) Lamella that encircles the base of antennal scape entire.

(6) Anterior clypeal margin with at most three denticles (i.e., a median denticle and one on each side), but sometimes the median tooth is indistinct so that only two denticles are seen on the margin.

(7) Ventral surface of clypeus smooth or bearing a weak transverse ruga but lacking toothlike prominences.

(8) Palp formula 1,3 in 10 species examined.

(9) Frontal carinae extending to the level of the posterior margins of eyes.

(10) Well-developed scrobes absent.

(11) Dorsum of alitrunk in profile more or less arched, in dorsal view without any sutures.

(12) Pronotum usually unarmed but with a pair of small teeth in one species (P. minusculus).

(13) Petiole node in profile high, higher than the length of the node, usually with a distinct anterior face, but in P. inermis, the anterior face of the petiole node is inseparable from the dorsal surface of the peduncle.

(14) Dorsal surfaces of head and alitrunk smooth or with scattered foveolate punctures or with foveolate-reticulate sculpture.

Profundus Group

Malaysia.

The profundus group is closely related to the levigatus group. The form of dentition of the masticatory margin of the mandible is a critical character shared by the workers and queens of the two groups. Possessing so many autapomorphic characters, including that a tooth on the basal margin of the mandible is adjacent to the basal tooth of the masticatory margin, as well as the previously mentioned characters 3 to 6, the profundus group is easily separable from the levigatus group and all other Pristomyrmex species groups.

Worker. Small sized, with the following combination of characters.

(1) Masticatory margin of mandible lacking a diastema and possessing four teeth (i.e ., the strongest apical + the second strongest preapical + the smallest third + an acute basal tooth); basal margin of mandible with a strongly prominent tooth that is adjacent to the basal tooth of the masticatory margin; as a result, five teeth are set close together.

(2) Lateral portions of clypeus in front of antennal fossae reduced to margins.

(3) Antennal scrobes broad, deep , and extending close to the occipital corners.

(4) Base of antennal scape lacking a circling lamella.

(5) Mesonotum much higher than propodeal dorsum so that the dorsum of alitrunk in profile is not continuously arched.

(6) Metapleural lobes vestigial and indistinct.

Punctatus Group

The punctatus group differs from the cribrarius group by lacking a pair of pronotal spines in the workers and by showing the anterior face of the petiole node not distinct from the upper surface of peduncle in the female castes. The punctatus group differs from the quadridens group by possessing palp formulae of 5,3 and 4,3 (the quadridens group possesses palp formulae of 2,2, 1,3 and 2,3).

This group has five species. Four occur in the Oriental region, one of which (P. punctatus) has spread to warm-temperate areas in the eastern Palaearctic. The remaining species (P. fossulatus) is confined to South Africa. Pristomyrmex punctatus is a unique species within the genus. It is the only Pristomyrmex extending its range to the temperate zone, and it is further characterized by the possession of a unique life history that may preadapt it for dispersal by natural and human transport.

The punctatus group is closely related to the cribrarius and quadridens groups because all female castes of these species groups possess a distinct diastema after the preapical tooth on the masticatory margin of mandibles (except in P. trachylissus, which has five teeth on the masticatory margin). Though sharing the previously described mandibular character, the trispinosus group is relatively distant from the punctatus group because it possesses so many autapomorphic characters, for example, frontal carinae absent, dorsal alitrunk with a promesonotal suture or impression, propodeal spines in dorsal view showing a "fork", some regular striation present on the dorsal surfaces of head and alitrunk.

Worker. Small to medium sized (HL 0.62-0.98, HW 0.64-0.94, TL 2.62-3.44), with the following combination of characters:

(1) Masticatory margin of mandibles with three to four teeth arranged as the strongest apical + the second strongest preapical + a long diastema + two small basal denticles of similar size (or a broad basal tooth).

(2) Palp formula 5,3 in four Oriental species and 4,3 in the single South African species.

(3) Frontal carinae present.

(4) Lateral portions of clypeus reduced to a narrow margin in front of the antennal fossae in three species (P. punctatus, P. rigidus, and P. fossulatus) but developed in the other two species (P. divisus and P. pulcher).

(5) Frontal lobes indistinct or absent.

(6) Lamella that encircles the base of antennal scape, entire.

(7) Alitrunk in profile showing a continuous convex dorsum and in dorsal view lacking sutures.

(8) Pronotum unarmed.

(9) Propodeum with a pair of spines.

(10) Petiole node in profile more or less wedge-shaped, lacking distinct anterior face distinguishable from the upper surface of peduncle.

Quadridens Group

This group currently contains 25 species, accounting for almost half the genus. Of them, three occur in Africa, six in Australia and 16 in the Oriental region. In fact, like many Pristomyrmex, many species in this group have a restricted geographic range.

Worker. Usually medium- to large-sized ants (HL 0.73-1.46, HW 0.68- 1.62, TL 2.90- 6.48) with the following combination of characters.

(1) Masticatory margin of mandibles with three to five teeth , which have one of the following three arrangements:

a. the strongest apical + the second strongest preapical + a long diastema + two small teeth of similar size (or one basal tooth, which is sometimes formed by the fusion of the two small teeth) or

b. the strongest apical + the second strongest preapical + a diastema + three small teeth of similar size or

c. the strongest apical + the second strongest preapical + an intercalary small tooth + a very short diastema (or this diastema indistinct) + two small teeth of similar size (i.e. , as shown in P. trachylissus).

(2) Anterior clypeal margin with five or more denticles in most species, but several species having only three teeth or prominences.

(3) Lateral portions of clypeus in front of antennal fossae reduced to a margin, and the antennal fossae reaching the anterior clypeal margin.

(4) Palp formula 1,3 (in 11 species), or 2,2 (three specie s), or 2,3 (four species).

(5) Frontal carinae usually extending to the level of the posterior margins of eyes, with the exception in P. erythropygus, P. longispinus, P. trogor, and P. wilsoni.

(6) Frontal lobes indistinct or very weak.

(7) Antennal scrobes shallow or absent.

(8) Lamella, encircling the base of antennal scape, entire.

(9) Dorsum of alitrunk lacking pro-mesonotal suture.

(10) Pronotum armed with small teeth to well-developed spines, except in P. eduardi and P. orbiceps.

(11) Petiole node in profile usually high, with the anterodorsal angle elevated above the posterodorsal, but sometimes showing other forms.

(12) Dorsum of head without sculpture, with scattered foveolate punctures, or with foveolate-reticulate sculpture or rugoreticulum.

Trispinosus Group

This is a monophyletic group because it possesses many autapomorphic characters, such as characters 3, 4, 8, 9, 11, and 13. This group contains three native Mauritian species.

Worker. Medium-sized ants (HL 0.88-1.22, HW 0.82-1.16, TL 3.24-4.82) with the following combination of characters:

(1) Masticatory margin of mandibles with four teeth that have one of the following two arrangements:

a. the strongest apical + the second strongest pre apical + a relatively short (first) diastema + a small denticle + a relatively long (second) diastema + a small basal denticle, as in P. bispinosus and P. trispinosus (in P. trispinosus, sometimes the first diastema is somewhat indistinct) or

b. the apical + the preapical + a relatively long (first) diastema + a small denticle + a relatively short (second) diastema + a small basal denticle, as in P. browni; sometimes the second diastema is indistinct.

(2) Anterior margin of the median portion of clypeus with at least five denticles. Two ends of the anterior clypeal margin each with a developed subtriangular tooth. Lateral portions of clypeus reduced to a margin; thus, the antennal fossae reach the anterior clypeal margin.

(3) Palp formula 1,2.

(4) Frontal carinae absent.

(5) Frontal lobes almost completely absent.

(6) Antennal scrobes absent.

(7) Lamella that encircles the base of antennal scape entire.

(8) Dorsum of alitrunk with a promesonotal suture or impression.

(9) Alitrunk in profile with a convex promesonotum and a deeply concave propodeal dorsum.

(10) Pronotum with a pair of robust, short to moderately long spines.

(11) Propodeal spines long, in dorsal view joined together at the base so that they form a fork.

(12) Petiole with a long anterior peduncle that is longer than the length of the node.

(13) Foveolate punctures completely absent, but regular striations are present on the dorsal surfaces of the head and the alitrunk in P. trispinosus and P. browni and present on the genae and around the antennal sockets in P. bispinosus.

(14) First gastral tergite with numerous hairs.

Umbripennis Group

This is a monophyletic group, containing five valid species. It is easily recognizable by possessing characters 1, 2, 5, 8, and 14. This group is endemic in the Oriental region and restricted to the Philippines, Malaya, Singapore, Brunei, Sabah, Borneo, Indonesia, and Papua New Guinea.

The males of the umbripennis group are easily distinguished from the other known Pristomyrmex males by possessing the following characters: (1) medium to large size; (2) palp formula 1,3; (3) propodeum with a pair of broad-based, robust spines; and (4) the sides of petiole with some longitudinal or reticulate rugae.

Worker. Medium to large sized (HL 1.04-1.68, HW 1.02-1.74, TL 4.10-7.06) with the following combination of characters.

(1) Masticatory margin of mandibles with four teeth arranged as the strongest apical + the second strongest preapical + two broad-based short teeth of similar size; diastema lacking or indistinct.

(2) Basal margin of mandible with a central, broad-based, prominent lobe.

(3) Lateral portions of clypeus in front of antennal fossae reduced to a margin.

(4) Anterior margin of the median portion of clypeus usually with five to seven denticles; lateral portions of anterior clypeal margin in front of antennal fossae with a few weak blunt denticles.

(5) Ventral surface of clypeus with a transverse ridge.

(6) Frontal lobes present, partly covering the condylar bulbs of holding antennal scapes.

(7) Frontal carinae extending to the level of the posterior margins of eyes.

(8) Lamella that encircles the base of antennal scape usually with a broad and deep notch on the center of the dorsal surface.

(9) Palp formula 1,3.

(10) Eyes small; EL is about 0.040 to 0.064 X HW in P. picteti and P. pollux and 0.069 to 0.108 X HW in P. umbripennis.

(11) Alitrunk in profile, not including propodeal spines, with a regularly arched dorsum, in dorsal view without any sutures.

(12) Pronotum unarmed.

(13) Metapleural lobes bluntly rounded.

(14) Petiole node in profile longer than high, with a long anterior peduncle; its anterodorsal angle is on approximately the same level as the posterodorsal.

(1.5) Foveolate punctures or foveolate-reticulate sculpture present on the dorsal surfaces of the head and the alitrunk.