Key to Pristomyrmex of the Philippines

This worker key, and accompying text, is based on [[Media:Zettel 2006.pdf|Zettel, H. 2006. On the ants of the Philippine Islands: 1. The genus Pristomyrmex Mayr, 1866. Myrmecologische Nachrichten 8:59-68.]]

In general, intraspecific variability appears to be very low in species of Pristomyrmex, which makes identification relatively simple compared to many other myrmicine genera.

Ecology
Most species of Pristomyrmex dwell in the rainforest, foraging as predators or scavengers (Wang 2003). Of the species collected by the author, only P. punctatus has been found in obviously disturbed habitats; this species is the most widespread in the genus (see WANG 2003). All other Philippine species seem to be confined to humid forest habitats. Typical collection sites are wet, mossy rock faces or fallen tree trunks. Rarely, specimens have been observed foraging on leaves (a few specimens of Pristomyrmex longispinus and Pristomyrmex schoedli). A nest of Pristomyrmex quadridens has been discovered in a piece of rotten wood (dimensions about 15 × 20 × 50 cm) laying on the moist soil and rocks on a river bed. Usually specimens of Pristomyrmex are only collected in small numbers, but approximately 100 P. schoedli workers were collected within 10 minutes from a fallen log at Baybay (site #422) and numerous specimens remained uncollected, which suggests that nest sizes in Pristomyrmex can occasionally be high. Low worker numbers, large distance between specimens running on trails, and the relatively slow motion of undisturbed specimens make Pristomyrmex rather discreet animals. Nevertheless, Pristomyrmex seem to be rare organisms. Deforestation on many Philippine islands may already have reduced the diversity of those species, which are restricted to moist forests.

Species diversity and regional endemism in the Philippines
At present, 55 species of Pristomyrmex are described (Wang 2003, and this paper). Seventeen species are recorded from the Philippines (= 30.9 % of world fauna). Of these seventeen species, nine species seem to be endemic to the Philippines (= 16.4 % or one sixth of world fauna). The question, whether species are regionally endemic or not, needs to be answered with caution due to the relatively small number of collections.

Most species records are from Greater Mindanao (10 species), Greater Luzon (7 species), and Greater Negros-Panay (5 species), probably because of the more intensive collecting activities and more suitable habitats on the larger islands.

1

 * Pronotal spines not at all developed . . . . . 2


 * Pronotal spines developed, short and triangular or long . . . . . 6

2
return to couplet #1
 * Dorsal surface of head and alitrunk rugoreticulate . . . . . 3


 * Dorsal surface of head and alitrunk punctate or foveolate . . . . . 4

3
return to couplet #2
 * Femora and tibiae reddish or brown; basal margin of mandible with or without inconspicuous tooth . . . . . Pristomyrmex punctatus


 * Femora and tibiae yellow; basal margin of mandible with a broad tooth . . . . . Pristomyrmex pulcher

4
return to couplet #2
 * Masticatory margin of mandible without diastema; petiolar node in profile longer than high and distinct from peduncle. . . . . . Pristomyrmex picteti


 * Masticatory margin of mandible with diastema; petiolar node in profile higher than long or not clearly separated from peduncle . . . . . 5

5
return to couplet #4
 * Frontal carinae short, not extending to level of posterior margin of eye; masticatory margin of mandible with diastema . . . . . Pristomyrmex divisus


 * Frontal carina long, extending to level of posterior margin of eye; masticatory margin of mandible without diastema . . . . . Pristomyrmex simplex

6
return to couplet #1
 * Dorsal surface of head (and usually also alitrunk) rugoreticulate . . . . . 7


 * Dorsal surface of head and alitrunk smooth or punctate . . . . . 11

7
return to couplet #6
 * First gastral tergite with numerous, evenly distributed erect or suberect setae . . . . . Pristomyrmex hirsutus


 * First gastral tergite without erect or suberect setae . . . . . 8

8
return to couplet #7
 * Ventral surface of clypeus without central tooth . . . . . 9


 * Ventral surface of slypeus with a central tooth . . . . . 10

9
return to couplet #8
 * Pronotal spines very long (at least 0.36 mm), usually longer than distance between their bases . . . . . Pristomyrmex bicolor


 * Pronotal spines short (shorter than 0.30 mm), much shorter than distance between their bases . . . . . Pristomyrmex costatus

10
return to couplet #8
 * Pronotal spines very short (0.06-0.12 mm), at most as long as propodeal spines . . . . . Pristomyrmex brevispinosus


 * Pronotal spines relatively long (0.15-0.17 mm), distinctly longer than propodeal spines . . . . . Pristomyrmex rugosus

11
return to couplet #6
 * Pronotal spines triangular, short . . . . . 12


 * Pronotal spines long . . . . . 15

12
return to couplet #11
 * Dorsum of head with large foveolate punctures . . . . . Pristomyrmex quadridens


 * Dorsum of head with relatively fine punctures . . . . . 13

13
return to couplet #12
 * Petiolar node in profile without distinct anterior face or separated from upper surface of peduncle; head width 0.98-1.04 mm . . . . . Pristomyrmex flatus


 * Petiolar node in profile with anterior face distinctly separated from upper surface of peduncle; head width 0.77-0.94 mm . . . . . 14

14
return to couplet #13
 * Pronotal spines distinctly shorter than propodeal spines; antennal scrobes present, laterally delimited by ridge caudally at least to level of centre of eye . . . . . Pristomyrmex distinguendus


 * Pronotal spines subequal in length to propodeal spines; antennal scrobes absent, laterally not delimited by ridge . . . . . Pristomyrmex collinus

15
return to couplet #11
 * Clypeus with median carina . . . . . Pristomyrmex curvulus


 * Clypeus without median carina . . . . . 16

16
return to couplet #15
 * Petiolar node in profile lacking distinct anterior surface separated from dorsal surface of peduncle; propodeal spines relatively long (PSL2 0.18-0.26) . . . . . Pristomyrmex longispinus


 * Petiolar node in profile with distinct anterior surface separated from dorsal surface of peduncle; propodeal spines relatively short (PSL2 0.09-0.13) . . . . . Pristomyrmex schoedli