Key to South American Pogonomyrmex

Modified from: Taber S.W. 1998. The World of the Harvester Ants. Texas A&M University Press. College Station.

For North American Pogonomyrmex species go to the Key to North American Pogonomyrmex. There is currently one species known from Central America (i.e., as defined beginning south of Mexico; Taber's key to North America species includes Mexican species): Pogonomyrmex guatemaltecus. This ant's name is appropriate since it is currently only known from Guatemala. There are three validly named species from the Caribbean. All of these species are Hispaniola endemics and all are considered to be in the subgenus Ephebomyrmex (see the next paragraph and couplet 11E).

Towards the bottom of this page is Taber's key to Ephebomyrmex species. This genus is currently considered a synonym of Pogonomyrmex. Various publications have changed the status of this taxon from subgenus to genus many times in the last hundred years. Taber stated:

Ephebomyrmex and Pogonomyrmex are recognizable to tribe by their pectinate tibial spurs of the middle and/or hind legs. Pogonomyrmex are distinctive within the tribe by the presence of a psammophore. Ephebomyrmex have a poorly developed or lacking psammophore and a swollen clypeal plate. North American species can be identified to this group by a combination of: 1) lack of psammophore or only sparse setae present 2) dentary margin of mandible roughly tranverse 3) alitrunk profile almost continuous and roughly convex 4) cephalic sculpture coarsely rugo-reticulate 5) small size, 4-6 mm in length 6) docile behavior.

If you have a relatively small Pogonomyrmex with a sparse or non-existant psammophore you may wish to start with this other key.

1

 * interrugal areolation dense, presenting a beaded appearance . . . . . 2


 * interrugal areolation not dense enough to present a beaded appearance . . . . . 17

2
return to couplet #1
 * propodeum unarmed (with tubercles at best) . . . . . 3


 * propodeum armed with short or long spines . . . . . 4

3
return to couplet #2
 * dorsum of first gaster segment partly or entirely covered with conspicuous longitudinal rugae (in part) (Argentina, Bolivia) L = 6.0-7.0 mm . . . . . Pogonomyrmex longibarbis


 * dorsum of first gaster segment without rugae (Argentina) L = 5.0-6.5 mm . . . . . Pogonomyrmex inermis

4
return to couplet #2
 * humeral angles rounded, not sharp . . . . . 5


 * humeral angles sharp (not smoothly rounded) . . . . . 6

5
return to couplet #4
 * scape base strongly developed, trumpet-shaped (Chile) L = 7.8-8.0 mm . . . . . Pogonomyrmex bispinosus


 * scape base only moderately developed, not flared into trumpet-shape (Argentina, Uruguay) L = 5.5-6.5 mm . . . . . Pogonomyrmex uruguayensis

6
return to couplet #4
 * head, alitrunk, and abdomen all black or blackish (I have heard that red-headed P. carbonarius workers exist, but I have not seen any nor have I encountered them in a published report.) . . . . . 7


 * of head, alitrunk, and abdomen, at least one not black or blackish . . . . . 9

7
return to couplet #6
 * propodeal spines connected by prominent keel, dorsum of first segment of gaster mostly or entirely covered by conspicuous longitudinal rugae (Argentina) L = 6.5-7.0 mm . . . . . Pogonomyrmex carbonarius


 * propodeal spines lacking a prominent connecting keel . . . . . 8

8
return to couplet #7
 * basal margin of mandible roughly straight, not convex, at least one mandible with 7-8 teeth (Argentina) L = 6.5-7.0 mm . . . . . Pogonomyrmex atratus


 * basal margin of mandible at least slightly convex, usually at least one mandible with only 6 teeth (in part) (Argentina, Chile) L = 4.9-7.5 mm . . . . . Pogonomyrmex vermiculatus

9
return to couplet #6
 * metasternal flanges absent, weak, or difficult to discern with alitrunk in profile view . . . . . 10


 * metasternal flanges at least moderately developed, clearly visible with alitrunk in profile (more typical of the genus) . . . . . 11

10
return to couplet #9
 * dorsum of first gaster segment without rugae (Argentina) L = 8.0-8.5 mm . . . . . Pogonomyrmex laticeps


 * dorsum of first gaster segment entirely or mostly covered with longitudinal rugae (in part) (Argentina, Bolivia) L = 6.0-7.0 mm . . . . . Pogonomyrmex longibarbis

11
return to couplet #9
 * metasternal flanges very large (reminiscent of some Ephebomyrmex species), head and gaster orange, alitrunk black, basal face of propodeum in profile almost horizontal, rugae covering dorsum of first gaster segment (Argentina) L = 6.0-7.8 mm . . . . . Pogonomyrmex rastratus


 * lacking above character combination . . . . . 12

12
return to couplet #11
 * antenna scape short, in repose not greatly surpassing posterior corner of eye (Argentina) L = 6.5 mm . . . . . Pogonomyrmex meridionalis


 * antenna scape long, in repose approaching or exceeding midpoint between corner of eye and occiput . . . . . 13

13
return to couplet #12
 * head red or reddish . . . . . 14


 * head black . . . . . 15

14
return to couplet #13
 * ammochaetae of psammophore long (in part) (Argentina, Bolivia) L = 6.0-7.0 mm . . . . . Pogonomyrmex longibarbis


 * ammochaetae of psammophore short (in part) (Argentina, Chile) L = 4.9-7.5 mm . . . . . Pogonomyrmex vermiculatus

15
return to couplet #13
 * in full-face view, conspicuous interrugal reticulation covering most of head, head and alitrunk black, gaster orange or red . . . . . 16


 * in full-face view, any conspicuous interrugal reticulation is confined to posterior half of head (in part) (Argentina, Chile) L = 4.9-7.5 mm . . . . . Pogonomyrmex vermiculatus

16
return to couplet #15
 * dorsum of first segment of gaster entirely covered by longitudinal rugae (Argentina) L = 7.0-8.0 mm . . . . . Pogonomyrmex catanlilensis


 * dorsum of first segment of gaster without rugae (Argentina) L = 7.0 mm . . . . . Pogonomyrmex pronotalis

17
return to couplet #1
 * propodeum lacking spines (tubercles at best), rugae or striae present on dorsum of first gaster segment at insertion of postpetiole, basal margin of mandible roughly straight (Ecuador) L = 4.5-5.5 mm . . . . . Pogonomyrmex theresiae


 * propodeum with spines, rugae or striae absent from dorsum of first gaster segment, basal margin of mandible at least slightly convex . . . . . 18

18
return to couplet #17
 * scapes long, in repose approaching or exceeding midpoint between corner of eye and occiput (Argentina, Brazil, Uruguay) L = 7.5-9.0 mm . . . . . Pogonomyrmex lobatus


 * scapes short, in repose not greatly surpassing posterior corner of eye . . . . . 19

19
return to couplet #18
 * metasternal flanges in profile poorly developed, inconspicuous or absent . . . . . 20


 * metasternal flanges in profile conspicuous, more typical of the genus . . . . . 21

20
return to couplet #19
 * scape base with conspicuous depression or trough, femur of foreleg weakly incrassate at best, propodeal spines without connecting keel, worker caste strongly polymorphic with big-headed majors (Argentina, Uruguay) L = 7.5-12.0 mm (including major) . . . . . Pogonomyrmex coarctatus


 * scape base trough absent or weak, femur of foreleg strongly incrassate, propodeal spines with connecting keel, worker caste weakly polymorphic (Argentina) L = 7.2-9.0 mm . . . . . Pogonomyrmex bruchi

21
return to couplet #19
 * occipital corners with conspicuous rugae or striae, lateral clypeal projections only moderately developed (Argentina, Brazil) L = 6.5-8.0 mm . . . . . Pogonomyrmex micans


 * occipital corners without conspicuous rugae or striae, lateral clypeal projections strongly developed (Bolivia) L = 7.0-9.0 mm . . . . . Pogonomyrmex marcusi

. =II. Key to Ephebomyrmex=

1E

 * dorsum of basal segment of gaster with longitudinal rugae or striae . . . . . 2E


 * dorsum of basal segment of gaster without longitudinal rugae or striae . . . . . 5E

2E
return to couplet #1E
 * dorsum of basal segment of gaster entirely or mostly covered by rugae or striations (Colombia, Guyana) L = 7.6-9.0 mm . . . . . Ephebomyrmex mayri (= Pogonomyrmex mayri)


 * rugae or striae of dorsum of basal segment of gaster confined to basal half of segment, sometimes found only near insertion of postpetiole . . . . . 3E

3E
return to couplet #2E
 * anterior margin of clypeus convex, with small median triangular tooth (Venezuela) L = 5.0 mm . . . . . Ephebomyrmex abdominalis (= Pogonomyrmex abdominalis)


 * anterior margin of clypeus slightly excised or almost straight, but not broadly convex, margin without a small median triangular tooth . . . . . 4E

4E
return to couplet #3E
 * petiole and postpetiole not massive (much of South America) L = 4.0-5.0 mm. . . . . Ephebomyrmex naegelii (= Pogonomyrmex naegelii)


 * petiole and postpetiole massive (southern South America) L = 4.0-4.5 mm. . . . . Ephebomyrmex abdominalis (= Pogonomyrmex abdominalis)

5E
return to couplet #1E
 * maxillary palps with 5 segments, labial palps with 4 segments . . . . . 6E


 * b. maxillary palps with 4 segments, labial palps with 3 segments . . . . . 8E

6E
return to couplet #5E
 * head and alitrunk yellow or reddish, but not black (Argentina, Chile) L = 4.4-4.8 mm . . . . . Ephebomyrmex odoratus (= Pogonomyrmex odoratus)


 * head and alitrunk black or blackish . . . . . 7E

7E
return to couplet #6E
 * occiput and much of thoracic dorsum smooth, shining, few if any reticulations present, same for dorsum of petiolar node (Argentina, Chile) L = 4.5-5.0 mm . . . . . Ephebomyrmex laevigatus (= Pogonomyrmex laevigatus)


 * occiput with prominent reticulations and areolations, same for dorsum of thorax and petiolar node (Argentina, Chile) L = 4.6-6.0 mm . . . . . Ephebomyrmex angustus (= Pogonomyrmex angustus)

8E
return to couplet #5E
 * alitrunk in profile with distinct mesopropodeal depression, so that profile is not broadly convex (South America) . . . . . 9E


 * alitrunk in profile without distinct mesopropodeal depression, so that profile is broadly convex . . . . . 10E

9E
return to couplet #8E
 * head and alitrunk yellow, orange, or red, but not black (southern South America) L = 6.2-9.4 mm (worker), L = 12.0 mm (ergatogyne) . . . . . Ephebomyrmex cunicularius (= Pogonomyrmex cunicularius)


 * head and alitrunk black or blackish red (Argentina) L = 5.0-7.0 mm . . . . . Ephebomyrmex brevibarbis (= Pogonomyrmex brevibarbis)

10E
return to couplet #8E
 * anterior margin of clypeus broadly convex, head and alitrunk blackish or blackish red, setae of dorsum of basal segment of gaster erect or semierect and black (Haiti) . . . . . 11E


 * anterior margin of clypeus excised or straight, but not broadly convex, head and ali trunk yellow, red, or reddish brown, but never blackish (not Haiti) . . . . . 12E

11E
return to couplet #10E
 * petiolar node in dorsal view fan-shaped or shaped like baseball catcher's mitt (rugae present but rather sparse) (Haiti) L = 5.0-5.5 mm . . . . . Ephebomyrmex saucius (= Pogonomyrmex saucius)


 * petiolar node in dorsal view miter-shaped (node covered with coarse rugae) (Haiti) L = 3.5-4.5 mm . . . . . Ephebomyrmex schmitti (= Pogonomyrmex schmitti) (and there is also a Hispaniola subspecies that was not included in Taber's key Pogonomyrmex schmitti aterrimus)

12E
return to couplet #10E
 * lateral clypeal projections prominent . . . . . 13E


 * lateral clypeal projections absent or very weak . . . . . 14E

13E
return to couplet #12E
 * propodeal spines absent, dorsum of petiolar node with little or no rugae, the surface almost smooth (Baja California) L = 3.5 mm . . . . . Ephebomyrmex laevinodis (= Pogonomyrmex laevinodis)


 * propodeal spines present, dorsum of petiolar node with conspicuous rugae (U.S., Mexico) L = 4.0-4.8 mm . . . . . Ephebomyrmex imberbiculus (= Pogonomyrmex imberbiculus)

14E
return to couplet #12
 * dorsum of basal segment of gaster with fine and appressed setae (lying flat or nearly so against the surface), dorsum of segment smooth and shining (not shagreened) (Argentina, Paraguay) L = 5.0 mm . . . . . Ephebomyrmex tenuipubens (= Pogonomyrmex tenuipubens)


 * setae on dorsum of basal segment of gaster erect or suberect (not appressed), dorsum of gaster at least lightly shagreened (U.S., Mexico) L = 3.5-4.0 mm . . . . . Ephebomyrmex pima (= Pogonomyrmex pima)