Key to Pristomyrmex of the Phillipines

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This worker key, and accompying text, is based on 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.

Key to Workers

1

  • 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
Head of Pristomyrmex punctatus worker
Profile of Pristomyrmex punctatus worker
  • Femora and tibiae yellow; basal margin of mandible with a broad tooth . . . . . Pristomyrmex pulcher
Head of Pristomyrmex pulcher worker
Profile of Pristomyrmex pulcher worker

4

return to couplet #2

  • Masticatory margin of mandible without diastema; petiolar node in profile longer than high and distinct from peduncle. . . . . . Pristomyrmex picteti
Head of Pristomyrmex picteti worker
Profile of Pristomyrmex picteti worker
  • 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
Head of Pristomyrmex divisus worker
Profile of Pristomyrmex divisus worker
  • Frontal carina long, extending to level of posterior margin of eye; masticatory margin of mandible without diastema . . . . . Pristomyrmex simplex
Head of Pristomyrmex simplex worker
Profile of Pristomyrmex simplex worker

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
Head of Pristomyrmex bicolor worker
Profile of Pristomyrmex bicolor worker
  • Pronotal spines short (shorter than 0.30 mm), much shorter than distance between their bases . . . . . Pristomyrmex costatus
Head of Pristomyrmex costatus worker
Profile of Pristomyrmex costatus worker

10

return to couplet #8

Profile of Pristomyrmex brevispinosus worker
  • Pronotal spines relatively long (0.15-0.17 mm), distinctly longer than propodeal spines . . . . . Pristomyrmex rugosus
Head and profile of Pristomyrmex rugosus worker

11

return to couplet #6

12

return to couplet #11

Profile of Pristomyrmex quadridens worker

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
Head of Pristomyrmex flatus worker
Profile of Pristomyrmex flatus worker
  • 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
Head and profile of Pristomyrmex distinguendus worker
  • Pronotal spines subequal in length to propodeal spines; antennal scrobes absent, laterally not delimited by ridge . . . . . Pristomyrmex collinus
Head of Pristomyrmex collinus worker
Profile of Pristomyrmex collinus worker

15

return to couplet #11

Head of Pristomyrmex curvulus worker
Profile of Pristomyrmex curvulus worker

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
Profile of Pristomyrmex longispinus worker
  • 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
Head and profile of Pristomyrmex schoedli worker