Key to Camponotus species in or possible in MS and AL

(from Creighton 1950, Snelling 1988; Mark Deyrup, pers. comm., William MacKay-Camponotus website)
1  The head of major abruptly truncated in front, circular in cross section, the truncated part consists of the clypeus and the adjacent parts of the cheeks; no intermediate sized workers present (medias)
...2 (subgenus Colobopsis)
  The head of major not truncated; medias present
...4
2(1)  

The angle where the side of the head meets the truncated anterior face with a distinct flange or rim; the sculpture of the anterior face with small shallow punctures and fine reticulation; truncated face somewhat shining; metanotal suture shallowly or not impressed on both major and minor
 

The angle where the side of the head meets the truncated anterior face without a flange or rim, but instead either serrate or blunt; the anterior face coarsely punctate with heavy reticulation; metanotal suture shallowly to deeply impressed

..3
3(2)  Major workers with large, coarse, and sharp reticulations or foveolate punctures present on side of head and on truncated area of head, with edges of punctures touching one another; numerous erect hairs present on top of head (best seen in profile); metanotal suture of alitrunk of major and minor shallowly impressed; propodeum angulate between dorsal and declivious faces; generally smaller in size, majors usually 3.75 mm or less in overall length
  Reticulations or foveolate punctures on head of major smaller, less deep, and not usually touching each other; few erect hairs present on posterior area of head; metanotal suture of both major and minor deeply impressed; propodeum usually rounded between dorsal and declivious faces; usually large, major workers 4.5 mm or more in total length
4(1)  The scapes and legs with long, coarse, brown or golden, erect hairs on all surfaces
...5 (subgenus Myrmothrix)
  Scapes and legs without long erect hairs
...7
5(4)  Larger size, total length of major about 10 mm, TL of minors about 7 mm, TL of queen about 14 mm; alitrunk arched over entire length
....6 (subgenus Myrmothrix)
  Smaller, TL of major about 5 mm, TL of minor about 4 mm, TL of queen about 8 mm; alitrunk deeply impressed at metanotal suture
...sexguttatus (Fabricius) (subgenus Myrmosphincta)
6(5)  Head and alitrunk reddish colored with gaster dark brownish to blackish colored (found on the coast)
 

Head brownish red and the rest of the body a concolorous golden brown (Introduced ant, probably not established. I am not exactly sure what is going on with this group, there seems to be some confusion, but for now I'm going with this)
7(4)   The thorax stout, no longer than the head excluding mandible; the pronotal humeral angles are well marked
  The thorax longer and much longer than head; humeral angles are rounded
...8
8(7)  The anterior margin of the clypeus feebly projecting and depressed in the middle with a narrow, median notch, behind which is a short, triangular impression; the total length of the major does not exceed 8 mm
...9 (subgenus Myrmentoma)
  The anterior margin of the clypeus not projecting and usually without notch medially, but if there is a notch present then there is no triangular impression behind it; the length of the major rarely less than 8 mm and usually much more
....14
9(8)  The malar area with conspicuous suberect to erect hairs that arise from coarse and somewhat elongate foveae
...10
  Malar area without suberect or erect hairs (sometimes a few near the base of mandibles) and malar area punctate, but without elongate foveae
...12
10(9) Clypeus with usually less than 12 long, erect hairs which are found along and adjacent to margins of clypeus (none of these hairs as short as those found on malar area) with few on clypeal disc (0-3); the gaster usually with transverse light and dark brown stripes (in woods under rotting logs, etc.)
...subbarbatus Emery
  The clypeus with more than 20 (usually) erect hairs, many of these (especially those found in mid-clypeal region) as long as erect hairs on malar area; gaster usually colored dark brown to black
...11
11(10) Erect hairs on clypeus of varying lengths with the shortest hairs being about the same length as those on the malar region; color light to dark brown
  Erect hairs on the clypeus of two distinct lengths, long and short, with the short hairs being shorter than those on the malar region; the head, alitrunk, petiole, and appendages red, and the gaster blackish
Note:  Some consider C. caryae and C. discolor to be a single species, C. caryae. 
12(9) Color either completely black or brownish-black, or head, alitrunk, petiole, and first to second gastral tergites yellowish to yellowish-red with the rest of the gaster blackish
...13
  Head, alitrunk, and petiole reddish colored, gaster black
13(12) The head and alitrunk dark brownish-black to black
  The head, alitrunk, appendages, and the first 1 or 2 gastral tergites yellowish to yellowish-red
Note:  Some taxonomists consider C. decipiens, nearcticus, and snellingi to be a single species, C. nearcticus.
14(8) The occipital corners covered with numerous erect hairs; gaster opaque or shining
...18
  Occipital corners without numerous erect hairs; gaster usually shining (at least feebly) to opaque, gaster not banded
...15
15(14) Both alitrunk and gaster uniformly reddish colored
...16
  Alitrunk black or with some reddish color, but gaster either entirely black or black with some reddish color near base where it joins with the petiole
...17
16(15) Cheek with numerous erect hairs (especially in majors); head usually completely to mostly black, the rest of body reddish colored (this ant is very similar looking to C. castaneus)
...americanus Mayr (subgenus Camponotus)
  Cheek with few or no erect hairs (if present then usually restricted to the area just above the mandible); color a uniform oranish-red, occasionly the head is a darker shade than the rest of body, but not black
...castaneus (Latreille) (subgenus Tanaemyrmex)
17(15) Body usually black, but occasionly some reddish color at base of legs or legs may be mostly reddish-brown; the appressed hairs on the gaster are less numerous and barely overlap the posterior edges of the gastral tergites, usually much less than a third of the total hair length extends past the edge, hairs more silvery-white in color (common)
...pennsylvanicus (DeGeer) (subgenus Camponotus)
  The posterior part of propodeum, the petiole, the base of gaster, and legs usually reddish, the rest of the body black (color is variable, sometimes there is less red present); the appressed hairs found on gaster are more numerous and long, they overlap the posterior edges of the gastral tergites (best seen in dorsal view) by at least half of their lengths and are golden in color (common)
...chromaiodes Bolton (subgenus Camponotus )
18(14) Middle and hind tibia lacking erect bristles arranged in a graduated row on flexor surfaces; bicolored with head and alitrunk reddish and gaster blackish
...tortuganus Emery (subgenus Tanaemyrmex)
  Middle and hind tibia with a row of erect bristles arranged in graduated row on flexor surfaces; color variable
...19
19(18) Head broader than long; scape flattened at base and often lobe-like as well; scape barely reaching occipital corners or only by the length of less than one funicular segment; color variable, but gaster not having transverse dark bands
....sansabeanus (Buckley) (subgenus Tanaemyrmex)
  Head not broader than long, but more elongate; scape not flattened at base; scape extending far beyond occipital corners, by about half the length of scape; color reddish-brown with gaster sometimes darker and usually with transverse dark bands (southern portions of MS and AL)
...socius Roger (subgenus Tanaemyrmex)