Key to Pheidole species in the southeastern United States

(modified from Creighton 1950, Gregg 1958 and Wilson 2003)

Major workers are needed for the first half of the key and minors are useful to have on hand as well. The second part of the key is a key to minor workers (to minor worker key). It is recommended that the key to majors be used because the characters are more definitive.

1          Head of major cylindrical in cross-section and obliquely truncate in front, the truncation involving the clypeus, frontal area, and mandibles
  Head of major not cylindrical in cross-section and not truncate
....2
2(1)     The hypostomal border of the head of the major has 4-5 teeth present
..3
  The hypostomal border of the major has 0-3 teeth
....15
3(2)   Scape of major flattened at base; large ants with head width of major 1.2-1.6 mm; head of major heart shaped with occiput having deep cleft in the middle and having rounded sides in full face view; minors with occiput broad in frontal view and lacking nuchal collar
...4
  Scape of major not flattened at base; ants either small with head width of major less than 1.2 mm or extremely large with head width greater than 1.6 mm; head of majors usually rectangular or somewhat quadrate in shape with occiput usually having shallow cleft and straight or weakly convex sides as seen in full face view; minors usually with occiput narrowed and having nuchal collar
...7
4(3)     As seen in profile, first tergite of gaster and dorsum of pronotum of major without pilosity present or with very little present; in full face view, head of minor completely foveolate and opaque
  As seen in profile, first tergite of gaster and dorsum of pronotum of major with abundant hairs; head of minor foveolate and opaque only on sides of head with a wide median strip down on the face devoid of foveolate sculpture and not opaque
...5
5(4)  Few or no erect hairs on waist
  Numerous long erect hairs present on waist, hairs at least as long as the maximum length of the eye
...6
6(5)    In profile, hairs on first gastral tergite mostly as long or longer than the maximum length of the eye; at least a few erect hairs present on occiput; color dark brown
  In profile, many hairs on first gastral tergite mostly much shorter than eye length; no erect hairs on occiput; color reddish brown
...sp. (crassicornis group)
7(3)       Propodeal spine of both major and minor reduced to at most a small denticle whose apex forms a right angle
  Propodeal spine of both major and minor strongly developed with the shaft longer than the base is broad
...8
8(7)    In profile, the alitrunk and head of both major and minor mostly lacking sculpture and strongly shining
  In profile, at least the side of propodeum and the mesopleurae, and often the sides of the pronotum of the majors and minors with sculpture, not shiny, but opaque
...9
9(8)  In full face view, head of major with moderate to heavy rugoreticulation present, especially occipitally
...10
  In full face view, head of major either not having rugoreticulation present or having only very little and when present restricted to the area between the eye and antennal fossae
...12
10(9) Large, head width of major greater than 1.6 mm; scape of major abruptly bent and thickened at base; transverse carinulae present on side of pronotum (coastal, introduced)
  Smaller size, head width less than 0.90 mm; scape of major not bent abruptly or thickened at base; transverse carinulae absent from side of pronotum
...11
11(10) The inner pair of hypostomal teeth of the major are reduced to denticles and are much smaller than the outer pair; the major has rugoreticulum restricted to the occiput and extending anteriorly down the side of the head to the eye and some between the eye and antennal fossa; the dorsal half of the head of the minor lacks carinulae; the coloration of the minor is blackish brown with distinct blueish or violaceous metallic reflections
  The inner pair of hypostomal teeth of the major are strongly developed and are as long as the outer pair; the major has rugoreticulum covering most of head in full face view except the frontal lobes and vertex which are carinulate; in the minor longitudinal carinulae and sometimes some rugoreticulum cover the posterior dorsal half of the head; in the minor the alitrunk is light reddish brown, the waist and gaster dark yellow, and there are no metallescent reflections present (a forest inhabiting ant)
12(9)  Side of pronotum of both major and minor lacking sculpture and is shiny in appearance; in full face view, at least the posterior half of head of both major and minor lacking sculpture and shiny in appearance (a very common ant found in many different habitats)
  Side of pronotum of both major and minor with foveolate sculpture, opaque; in full face view, posterior half of head of both major or minor with sculpture (longitudinal carinulae and or punctation) extending to or almost to occipital border
...13
13(12) The major has at least some rugoreticulum present on the head, either on or near the occiput, or between the eye and antennal fossae; the postpetiole of the major (seen from above) is less than 1.5 times as wide as the petiole
...14
  The major has no rugoreticulum present on dorsal surface of head; the post petiole of the major (as seen from above) is very broad, about twice as wide as petiole coastal)
14(13) The major with carinulae extending along the midline of the dorsum of head and reaching the occipital border (in full face view the occipital lobes are shiny), in lateral view the carinulae on the head (of major) barely extending beyond the eye posteriorly; the pronotum of the major has short, ill defined transverse carinulae laterally only; the head of the minor in lateral view with carinulae present only next to antennal fossa and sometimes on frontal lobes, no rugureticlum present near eye (in front view)
  The carinulae on the dorsum of the head of the major do not extend to the occipital border, therefore the occiput has a broader smooth face  in lateral view the carinulae on the head extend well past the eye posteriorly; the pronotum of the major has well defined transverse carinulae present dorsally; in lateral view the head of the minor has rugulae extending posterior to the eye and some loose rugoreticulum present between eye and antennal fossa (in front view) (coastal, introduced)
15(2)      Occiput of major with transverse carinulae or rugulae, opaque in appearance
...16
  Occiput of major smooth and shiny, or may be lightly to densely foveolate, but without carinalae, rugulae, or reticulatum
....17
16(15) Large ants, majors with head width about 1.6 mm; the side of the head of the major posterior to and laterad to the eye is smooth and shiny; the head and pronotum of the minor is completely foveolate and opaque; hairs on the dorsum of the alitrunk of the minor are simple (prairie, open grassy areas)
 

Smaller ants, majors with head width less than 1.2 mm; the side of the head of the major posterior to and laterad to the eye are foveolate and opaque; the head and pronotum of the minor is smooth and shiny; most of the hairs on the dorsum of the alitrunk are clavate

...soritis Wheeler (=sitarches, rufescens, & campestris)

17(15) Large ant, majors with head width greater than 1.25 mm; in profile the entire postpetiole of both major and minor is oval in shape with the ventral portion obviously convex; some rugoreticulum present between eye and antennal fossae on major; color brownish yellow (possible, found in southern FL, but this species is a tramp that gets around)
  Smaller ants, majors with head width less than 1.0 mm (most of the remaining species with HW < 0.60 except davisi, which is close approaching 1.0 mm, however davisi has sculpture on the side of pronotum in both major and minor whereas megacephala doesn't); in profile the entire postpetiole of minor and major not oval; no rugoreticulum present on face
...18
18(17) The entire side of alitrunk of major with parallel longitudinal carinulae
...19
  The mesopleuron and usually most of the side of pronotum of the major without parallel longitudinal carinulae
...20
19(18) The dorsum of pronotum of major covered with transverse carinulae; dorsum of mesonotum with longitudinal carinulae and foveolate making surface appear opaque; hypostomal border of major with three teeth; the pronotum of the minor is foveolate and opaque
  Dorsum of promesonotum smooth, shiny; hypostoma with less than 3 teeth; pronotum of minor smooth and shiny
20(18)   Dorsum of pronotum of major covered with transverse carinulae or rugulae; longitudinal carinulae on head of major reaching middle of occipital border (occipital lobes lacking sculpture though); petiole emarginate as seen from front to back; head and sides of alitrunk of minor foveolate and opaque (this ant is quite similar to pilifera, but it has occipital lobes of major unsculptured, is more orangish in color rather than reddish brown, and is smaller)
  Dorsum of pronotum of major with at most 2 patches of carinulae; the longitudinal carinulae on head of major do not reach occipital border; petiole of major not emarginate from front to back view; head of minor mostly shining, not foveolate and opaque, especially the posterior two thirds of face, side of pronotum mostly smooth and shiny
....bicarinata Mayr (common, P. vinelandica is now included here)
Key to minor workers of Pheidole
1     Propodeal spines reduced to mere denticles
...2
  Propodeal spines present and obvious
...3
2(1)    Sides of alitrunk, petiole, and postpetiole without sculpture or with very little; in profile the pronotum and the mesonotum forming an even, convex curve
  Mesopleurae, metapleurae, and sides of the petiole and postpetiole with sculpture; the pronotum and mesonotum not forming an even convexity, but more clearly separated
3(2) Occipital area of head strongly shining and mostly free from sculpture
...4
  Occipital area opaque and with some form of sculpturing present (even if only near lobe area and leaving central strip of face free sculpture)
...12
4(3)   Evenly spaced pairs of clavate hairs present on promesonotal dorsum and with similar hairs on petiole and postpetiole (best seen in profile); eyes very large [also keys later, some specimens have sculpture present on occipital area of head]
  Hairs on promesonotal dorsum and waist simple; eyes smaller, normal sized
...5
5(4)  In profile, the sides of alitrunk and waist with little or no sculpture, very shiny in appearance, golden colored (some punctures present along metanotal groove and sometimes mesopleurae)
  In profile, sides of alitrunk and waist with sculpture (sometimes without sculpture on side of pronotum)
....6
6(5)   The mesonotum depressed below the adjacent level of the pronotum so that in profile it forms a distinct step or angular projection between the pronotum and the propodeum
...7
  The mesonotum not depressed below the adjacent level of the pronotum and in profile the two usually forming an even convexity (in metallescens there is a slight dip where the pronotum joins the mesonotum)
...8
7(6)  Size larger, HL 0.80; in full face view the occipital corners rounded and posterior part of head elliptical, occipital margin rounded; nuchal collar visible in full face view; the first gastral tergite with a median fringe shagreened anteriorly (coastal, introduced)
  Size smaller, HL about 0.58; in full face view the occipital corners not so rounded, not giving the posterior part of head an elliptical appearance and the occipital margin feebly concave; nuchal collar not visible in full face view; the first gastral tergite without shagreening
8(6)   Body color blackish with blueish or violaceous reflections; sides of pronotum, the mesopleurae, and sides of propodeum foveolate and pronotal dorsum lacking sculpture (also keys out later as some specimens have foveate sculpture on heads rather than being shiny)
  Body color reddish brown to brownish black, without blueish or violaceous reflections; either with sides of pronotum with little or no sculpture (sometimes edges may have some, but at least centrally there is a definite lack of sculpture) and pronotal dorsum lacking sculpture, or entire side of alitrunk with sculpture with mesopleurae and sides of propodeum having longitudinal carinulae and dorsum of pronotum foveolate
...9
9(8)  Sides of pronotum with sculpture; longitudinal carinulae present on sides of propodeum and mesopleurae; pronotal dorsum and alitrunk foveolate; mesopleurae and sides of propodeum longitudinally carinulate
 

Sides of pronotum mostly or entirely without sculpture; pronotal dorsum mostly or entirely without sculpture

...10
10(9)
Color dark brownish black to black; deep rugo-reticulate sculpture on mesopleurae and side of propodeum; propodeal spines thickened, stout, blunt tipped
Orangish to reddish brown, occasionally darker brown; sculpture on mesopleurae and side of propodeum weaker, more punctulate; spines thinner, acute
...11
11(10)   In profile more longitudinal carinulae present on side of head between eye and antennal fossae and anteriorly to base of mandible as well as laterad to eye toward the ventral surface of head, these carinulae reach or surpass eye; postpetiole oval in shape
...bicarinata Mayr (includes vinelandica)
  In profile very little to no longitudinal carinulae present between eye and antennal fossae and none anteriorly between eye and base of mandible or laterad to eye toward ventral surface of head; postpetiole longer than wide and wider posteriorly than anteriorly (possible, not real likely, but found in southern FL, a tramp species)
12 (3)   Evenly spaced pairs of clavate hairs present on promesonotal dorsum and with similar hairs on petiole and postpetiole (best seen in profile); eyes very large [also keys earlier, some specimens lack obvious sculpture on posterior region of head]
  Hairs on promesonotal dorsum and waist simple; eyes small or large
...13
13(12)  Color dark brownish black with distinct blueish or violaceous reflections
  Color brownish to yellowish brown and without blueish or violaceous reflections
....14
14(13) The head mostly covered with carinulae and often somewhat reticulate, especially occipitally; color of head, mandibles, and alitrunk light reddish brown and waist, gaster, and appendages yellow (found in mesic forests)
  Carinulae and any reticulum restricted to the anterior half of the head; color variable
...15
15(14) The mesonotum depressed below the adjacent level of the pronotum so that in profile it forms a distinct step or angular projection between the pronotum and the propodeum; large size, HL 0.74, HW 0.62-0.66
...16
  The mesonotum not depressed below the adjacent level of the pronotum and in profile the two usually forming an even convexity; size usually smaller (except P. pilifera, which approaches the size of P. crassicornis)
...19
16(15) Head completely foveolate and opaque in full face view; concolous yellowish brown
  Head foveolate and opaque only on sides of head with a wide median strip down on the face devoid of foveolate sculpture and not opaque (the next 3 species are very similar in appearance to one another and are difficult, if not impossible to separate based on minors alone)
...17
17(16)   Longitudinal carinulae on face laterad of eye extending beyond eye posteriorly and longitudinal carinulae extending from near antennal fossae to within one third  of occipital border
...sp. (crassicornis group)
  Longitudinal carinulae on face laterad of eye not extending beyond eye posteriorly and longitudinal carinulae near antennal fossae barely extending or not extending beyond posterior portion of antennal fossae
...18
18(17)     Occipital area with many erect hairs present; in profile, head and dorsum of alitrunk, waist, and gaster with numerous long erect hairs present (hairs much more abundant than in P.diversipilosa), hairs on alitrunk dorsum as long or longer than length of eye
  Occipital area with few or no erect hairs present; in profile, head and dorsum of alitrunk, waist, and gaster with few erect hairs and hairs on dorsum shorter than length of eye (erect hairs more sparse and much shorter in length than erect hairs of P. tetra)
19(15) Some rugoreticulum present on head between eye and antennal fossae; rugulae extend posterior to eyes; color medium to dark brown ............ (found on coast at this time, introduced species)
 

No rugoreticulum present between eye and antennal fossae or elsewhere on head; color variable from yellow to light reddish brown

...20
20(21) Size larger, HL0.58-0.60; postpetiole not small and globular, more than 1.5 times as long as petiole
.....21
  Size smaller, HL 0.52-0.42; postpetiole small and globular, not much wider than petiole
...22
21(20) Color light reddish brown (prairies, open grassy habitats, etc.)
  Color yellowish brown, except head which is a slightly darker shade of brown (possible, northern FL, very similar looking to pilifera, but more orangish colored)
22(20)     Postpetiole and petiole foveolate and opaque on sides and also on dorsum; concolorous yellow; antennal club not greatly enlarged as compared to rest of funiculus (coastal, very similar to flavens)
  Petiole with foveolate sculpture only on sides and postpetiole without sculpture or only very little on sides and none dorsally; color medium to dark yellow; the antennal club much wider than the funiculus (possible, this species recorded from FL, where it was most likely introduced by commerce)