Note that this is a draft key that is missing some species (especially those in

the brevibarbis-group and most species with longitudinal striae on the first

gastral tergum). Please send comments or edits regarding the key so as to make

it more useful and accurate.

Species names given in apostrophes (“ “) represent unpublished manuscript names

(status changes and undescribed species) that are not to be used.

Pogonomyrmex of South America; key to species based on the worker caste

1 First gastral tergum lacking fine, dense striae, or striae sometimes

present near base, but not extending over most of tergum --------------- 2

-- First gastral tergum mostly covered with fine, dense (usually

longitudinal) striae -------------------------------------------------- ??

2 Head with scattered small foveae; in full-face view, part to all of

cephalic dorsum with fine longitudinal striae; antennal scapes short,

extending less than one-third the distance from posterior margin of eye

to posterior corner of head (coarctatus-group) ------------------------- 3

-- Head lacking foveae; in full-face view, cephalic dorsum with prominent

longitudinal rugae or rugoreticulate; scapes longer, extending more than

one-half the distance from posterior margin of eye to posterior corner

of head ---------------------------------------------------------------- 6

3 Striae cover most of dorsum of head, areas lacking striae shining to

strongly shining ------------------------------------------------------ 4

-- Striae cover entire dorsum of head, entire dorsum weakly shining ------ 5

4 Workers usually larger, strongly polymorphic with supermajors

(HW = 1.94-3.54); weak to moderately coarse rugae on posterior face of

petiole; rugae on dorsum of postpetiole absent or weak, usually

restricted to posterior margin; inferior propodeal spines lacking or

very reduced in size, broadly rounded; interrugal spaces on mesosoma

granulate, weakly shining ------------------------------------- coarctatus

-- Workers smaller, monomorphic (HW = 1.91-2.33); coarse rugae on posterior

face of petiole; weak to moderately coarse rugae on dorsum of postpetiole;

inferior propodeal spines pronounced, wider than long, apex bluntly

angulate to acute; interrugal spaces on mesosoma smooth, strongly

shining ---------------------------------------------------------- marcusi

5 In profile, lateral lobe of clypeus massively enlarged with narrow

gap (much less than width of antennal scape) between clypeal lobe and

frontal carina; concolorous ferruginous orange to orange-red ---- lobatus

-- In profile, lateral lobe of clypeus not enlarged with broad gap (similar

to width of antennal scape) between clypeal lobe and frontal carina;

bicolored, head dark red to reddish-black, gaster blackish -------- micans

6 In frontal view, head widest immediately posterior to mandibular

insertion; head elongate (CI < 90), posterior corners broadly rounded,

lacking a perceptible angle; HFI > 120; entire scape strongly striate;

psammophore poorly developed (consisting of hairs scattered over ventral

side of head) (cunicularius-group) ------------------------------------- 7

-- In frontal view, head widest posterior to eye; head subquadrate to

quadrate (CI > 90), posterior corners of head angulate; HFI rarely > 100;

scape smooth to partly striate; psammophore poorly to well developed --- 9

7 In lateral view, node of petiole rounded; inferior propodeal spines

wider than high, broadly rounded; first gastral tergum smooth and

polished, strongly shining; superior propodeal spines shorter than

distance between bases -------------------------------------- cunicularius

-- In lateral view, node of petiole angulate; inferior propodeal spines

about as wide as high, acuminate; first gastral tergum moderately

to strongly coriarious, dull to weakly shining; superior propodeal

spines longer than distance between bases ------------------------------ 8

8 Sculpturing on dorsum of mesosoma and posterior face of petiole coarse,

rugoreticulate to vermiculate; bicolored, mesosoma and petiole medium

to dark orangish-brown to reddish-brown, rest of body lighter -- “serpens”

-- Sculpturing on dorsum of mesosoma and posterior face of petiole weak

to moderately coarse, rugae irregular to weakly rugoreticulate;

body concolorous tannish-red ------------------------------- “pencosensis”

9 Superior propodeal spines absent or consisting of small to moderate sized

denticles or tubercles ------------------------------------------------ 10

-- Superior propodeal spines present, moderately to well developed ------- 11

10 Dorsum of postpetiole with regular to wavy transverse rugae ---- theresiae

-- Dorsum of postpetiole lacking transverse rugae ------------------- inermis

11 Dorsum of mesosoma smooth and shining, lacking rugae ------------------ 12

-- Dorsum of mesosoma with subparallel-parallel rugae, rugoreticulate, or

vermiculate, but never smooth and shining ----------------------------- 13

12 Body mostly concolorous blackish to black; juncture between anterior face

of petiole and peduncle rounded ------------------------------- laevigatus

-- Head and mesosoma light orangish-red, gaster slightly darker to brownish;

juncture between anterior face of petiole and peduncle angulate - odoratus

13 Superior and inferior propodeal spines long, acuminate; in profile,

posterior face of petiole with crest along anterior margin; ventral

margin of peduncle with acuminate spine; mesosoma with at least several

long flexuous hairs; anterior margin of clypeus with minute medial

tooth (sylvestris-group) ---------------------------------------------- 14

-- Superior and inferior propodeal spines rarely long and acuminate; in

profile, posterior face of petiole lacking crest along anterior

margin; ventral margin of peduncle straight or with triangular process,

but lacking acuminate spine; mesosoma usually lacking long flexuous hairs;

anterior margin of clypeus lacking minute medial tooth ---------------- 16

14 Larger species (HW > 1.55 mm); mandible with seven teeth; compound eye

lacking hairs between ommatidia; clypeus with prominent medial carina;

anterior margin of postpetiole not offset from helcium ------ striatinodis

-- Smaller species (HW < 1.35 mm); mandible with six teeth; compound eye

with hairs between ommatidia; clypeus lacking medial carina; anterior

margin of postpetiole offset from helcium ----------------------------- 15

15 Posterior face of petiole rugulose-punctate, dull to weakly shining;

in lateral view, procoxa transversely striate; femur and tibiae smooth

to weakly coriarious, weakly shining to shining ------------------ stefani

Posterior face of petiole smooth to undulated, shining; in lateral view,

procoxa finely imbricate; femur and tibiae very strongly coriarious,

dull ---------------------------------------------------------- sylvestris

16 Hairs on head (including psammophore) and mesosoma very short,

thin, and delicate, maximal length similar to width of cephalic

interrugae --------------------------------------------------- tenuipubens

-- Most hairs on head (including psammophore) and mesosoma not thin and

delicate, maximal length much longer than width of cephalic

interrugae ------------------------------------------------------------ 17

17 Dorsum of mesosoma and posterior face of petiole rugoreticulate to

vermiculate ----------------------------------------------------------- 18

-- Dorsum of mesosoma usually rugose, sometimes rugoreticulate to

vermiculate; posterior face of petiole with transverse or oblique rugae

or otherwise, but never rugoreticulate to vermiculate ----------------- 19

18 Small lobe projects dorsally from anterior margin of antennal fossa;

peduncle and anterior face of petiole meet at obtuse angle; in dorsal

view, posterior face of petiole narrow, width similar to or only slightly

greater than distance between tips of superior propodeal spines; mesosomal

hairs moderately short, longest rarely exceeding 0.7-0.8x MOD --- naegelli

-- Lacking small lobe that projects dorsally from anterior margin of antennal

fossa; peduncle and anterior face of petiole meet at or near right

angle; in dorsal view, posterior face of petiole distinctly wider than

distance between tips of superior propodeal spines; mesosomal hairs

longer, longest approaching to slightly exceeding MOD -------- abdominalis

19 Dorsum of postpetiole smooth and shining, granulate, punctate or

otherwise, but lacking rugae ------------------------------------------ 20

-- Dorsum of postpetiole with rugae ------------------------------------- 31?

20 Posterior face of petiole with transverse or oblique rugae ------------ 21

-- Posterior face of petiole smooth and shining, granulate, punctate or

otherwise, but lacking transverse or oblique rugae -------------------- 22

21 Base of scape not strongly compressed or flattened dorsoventrally;

in dorsal view, postpetiole width and length similar to slightly longer

than wide -------------------------------------------------- uruguayensis

-- Base of scape flattened, strongly compressed dorsoventrally; in dorsal

view, postpetiole wider than long ----------------------------- bispinosus

22 Interrugal spaces on dorsum and sides of mesosoma strongly granulate-

punctate, dull; eye small (MOD = 0.21-0.28), situated anterior to

middle of head; metanotal sulcus not impressed; body mostly concolorous

black ----------------------------------------------------------- angustus

-- Interrugal spaces on dorsum and sides of mesosoma smooth and shining to

moderately granulate-punctate, weakly shining to shining; eye larger

(MOD > 0.30), situated near middle of head; metanotal sulcus usually

present, slightly to moderately impressed; body concolorous dark brown

or bicolored (orangish-brown and brown) (brevibarbis-group) ----------- 23

23 Body bicolored (orangish-brown and brown); interrugal spaces on head

moderately to strongly granulate, dull to weakly shining; in profile,

petiolar node weakly rounded to angulate, elevated above rest of

petiole ------------------------------------------------------- “eremicus”

-- Body concolorous dark brown; interrugal spaces on head smooth, shining to

moderately granulate, weakly shining; in profile petiolar node usually not

angulate, not elevated above rest of petiole -------------------------- 24

24 Apex of petiolar node forming an acute tip ------------------– brevibarbis

Key out rest of brevibarbis group species -

31 Rugae on head and mesosoma fine and regular, interrugal spaces only

slightly wider than rugae; humeral angles enlarged, distinctly elevated

above medial portion of pronotum; head and mesosoma black, gaster dark

ferruginous orange -------------------------------------------- mendozanus

-- Rugae on head wavy to irregular, interrugal spaces distinctly wider than

rugae; rugae on mesosoma irregular, rugoreticulate, or vermiculate;

humeral angles flush with to slightly elevated above medial portion of

pronotum; color variable, but if head and mesosoma black and gaster dark

orange, then wide interrugal spaces on head are strongly granulate ---- 32

32 Interrugal spaces on head smooth to moderately coriarious, weakly shining

to shining ------------------------------------------------------------ 33

-- Interrugal spaces on head moderately to strongly granulate, dull ------ 34

33 Body concolorous black except for dark reddish band encircling eye; rugae

on promesonotum longitudinal, usually regular; rugae at medial occipital

margin longitudinal, rarely rugoreticulate ------------------- “tinogasta”

-- Head and mesosoma dark reddish-black, gaster black; rugae on promesonotum

transverse, oblique, or irregular, rarely longitudinal; rugae along medial

occipital margin usually partly rugoreticulate ------------------ laticeps

34 Body concolorous black ------------------------------------------- atratus

-- Body bicolored or concolorous, if concolorous then color is ferruginous

orange to reddish-orange ---------------------------------------------- 35

35 Body bicolored with the blackish-orange to black head and mesosoma and

ferruginous orange gaster ------------------------------------- pronotalis

-- Body concolorous or bicolored, if bicolored then gaster never lighter

than head and mesosoma ------------------------------------------------ 36

36 Bicolored with dark reddish head, rest of body black; in dorsal view,

cephalic rugae along posterior margin smooth and shining to moderately

granulate-punctate, weakly shining ------------------------- vermiculatus

Concolorous or with at least part of mesosoma darker than the ferruginous

orange head and gaster; in dorsal view, cephalic rugae along posterior

margin strongly granulate-punctate, dull -------------------- “intermedia”

Key for species with longitudinal striae on first gastral tergum

1 Entire body with very fine, dense, parallel-subparallel rugae; anterior

margin of clypeus with medial tooth -------------------------------- mayri

-- Body lacking very fine, dense, parallel-subparallel rugae; anterior

margin of clypeus entire ----------------------------------------------- 2

2 Head and mesosoma blackish to black, gaster dark orange to orangish-

black ------------------------------------------------------------------ 3

-- Body concolorous, or if bicolored then gaster never lighter than head

and mesosoma ----------------------------------------------------------- 4

3 Superior propodeal spines reduced to denticle or tubercle; in lateral

view, node of petiole rounded to subangulate -----------------– granulatus

-- Superior propodeal spines present, usually short, acuminate; in lateral

view, node of petiole angulate ----------------------------- catanlilensis

4 Superior propodeal spines well developed on at least some workers

in a series, spines usually >0.5x length between bases ----------------- 5

-- Superior propodeal spines reduced to triangular teeth, denticles,

tubercles, or lacking; if spines are present on occasional workers,

then length is < 0.3x distance between bases -------------------------- 12

5 Head and gaster ferruginous orange to reddish-orange, mesosoma black to

blackish, sometimes with slight orangish infusion on pronotum; inferior

propodeal spines usually moderately well developed, consisting of a broad

triangular process with rounded to acute tip --------------------------- 6

-- Coloration not as above (head often orangish to reddish, but never with

blackish to black mesosoma and orangish gaster); inferior propodeal spines

usually absent to poorly developed ------------------------------------- 8

6 Rugae on vertex absent to faint, interrugal spaces mostly smooth and

shining; metanotal sulcus usually present; regular to slightly wavy

longitudinal rugae on dorsum of mesonotum; interrugae on anterior

declivity of pronotum smooth and strongly shining -------------- “weiseri”

-- Rugae on vertex prominent, interrugal spaces granulate and dull or smooth

and shining; metanotal sulcus rarely present; rugae on dorsum of

mesonotum mostly irregular to rugoreticulate-vermiculate; interrugae on

anterior declivity of pronotum granulate, dull ------------------------- 7

7 Longitudinal rugae on promesonotum very irregular to vermiculate;

striae covering most to all of first gastral tergum --------- “neuquensis”

-- Longitudinal rugae on promesonotum slightly to moderately irregular;

striae occurring over no more than anterior one-half of first gastral

tergum, posterior portion smooth or coriarious --------------- “santschii”