Key to North American Crematogaster species

The following key to North American Crematogaster species has been modified from Morgan & Mackay (2017).

1

 * Postpetiole with two hemilobes, divided by longitudinal medial sulcus (look from above, Fig. 1 a; Plates 5 A and D); most common in temperate habitats
 * Postpetiole globular, not divided into two hemilobes by longitudinal medial sulcus (Fig. 1 b; Plates 5 B and C) or with slight emargination posteriorly (Fig. 1 c; Plate 5 E); most common in tropical and subtropical habitats

2

 * Petiole approximately as wide as long, trapezoidal, obviously widened anteriorly (Fig. 2, left; Plate 5 A)
 * Petiole subrectangular, not greatly widened anteriorly, sides nearly parallel (Fig. 2, right; Plate 5 D), if somewhat quadrate, widest medially not anteriorly

3

 * Base of spines not connected at widest portion of propodeum (Fig. 3, left; Plate 4 E)
 * Base of spines connected at widest portion of propodeum (Fig. 3, right; Plates 4 A, B, C, D and F)

4

 * Head and mesosoma punctate-lineolate (Fig. 4. left), following curvature of head and pronotal shoulder; México (southern Chihuahua to Veracruz) Crematogaster saussurei
 * Head longitudinally striate below eye; mesosoma punctate (Fig. 4, right); SW USA to northern México Crematogaster isolata
 * Note: Workers of Crematogaster nocturna, described only by queens and males collected at Rainbow Lodge, Navajo Mountains, Arizona, U. S. may key here due to similarities to the queens and males of Crematogaster nocturna with those of Crematogaster isolata.

5

 * Spines reduced (length from posterior edge of propodeal spiracle to tip 0.16 mm or less, see Fig. 5, left; Plate 4 A)
 * Spines longer (length as above 0.17 mm or more, see Fig. 5, right; Plate 4 B and C)

6

 * Head shiny and glossy medially, side of pronotum shiny, partially or completely smooth (Fig. 6, left); propodeal spines tiny, length approximately as long as width at base of spines (less than 0.13 mm in length)
 * Head at least partially sculptured medially in part of series; side of pronotum shiny or sculptured, usually punctate (Fig. 6, right); spines often longer than 0.13 mm, not greatly widened at base of spines

7

 * Concolorous light to dark brown, rarely bicolored (Fig. 7, left); rarely nesting in pine trees; common and widely distributed in southern and SE USA, southern Mexico Crematogaster ashmeadi
 * Bicolored with head and mesosoma red and gaster dark (Fig. 7, right); nesting in pine trees in Florida and Tennessee Crematogaster pinicola

8

 * Dorsum of head completely or nearly completely punctate (Fig. 8, left); mesosoma densely punctate; southern Arizona to southern México Crematogaster opaca
 * Dorsum of head partially smooth and glossy (Fig. 8, right); mesosoma rugose or shallowly costate; widely distributed

9

 * Medial mesonotal carina sharp and raised from surface (Fig. 9, left); side of pronotum mostly smooth and glossy; southeastern Texas and eastern México Crematogaster rifelna
 * Medial mesonotal carina poorly developed, barely raised from surface (Fig. 9, right); side of pronotum may be shiny, but is usually completely or nearly completely sculptured; widely distributed

10

 * Dorsal edge of propodeal spine sinuous (curved somewhat upwards distally) (Plate 4 B, Fig. 10); common in entire USA, northern Mexico Crematogaster cerasi
 * Dorsal edge of propodeal spine straight (Fig. 9, right); southwestern USA and NW México Crematogaster emeryana

11

 * Majority of specimens in series with 4 or fewer erect hairs on each pronotal shoulder (larger workers often have more hairs) (Fig. 11, left); mostly western USA and México
 * Pronotal shoulder of majority of workers with 5 or more erect hairs (Fig. 11, right); mostly eastern USA and eastern México

12

 * Side of pronotum shiny (Fig. 11, left); strongly bicolored (gaster black, remainder red, see Fig. 7, right); entire southern USA, eastern USA and México Crematogaster laeviuscula
 * Lateropronotum heavily sculptured (Fig. 11, right, Fig. 12); concolorous to slightly bicolored (see Fig. 7, left)

13

 * Pronotal shoulder with 1 to 4 erect hairs (Fig. 12, left) in majority of specimens in series
 * Pronotal shoulders completely without erect hairs (Fig. 12, right) in all specimens in series; SW USA, México Crematogaster depilis

14

 * Each posterior corner of petiole with small tooth (Fig. 13; Plate 25 B); southern and eastern USA to central México Crematogaster dentinodis
 * Posterior corners of petiole without teeth; widely distributed

15

 * Pronotum coarsely vermiculate (Fig. 14, left); western and southeastern USA to central México Crematogaster vermiculata
 * Pronotum shoulder with longitudinal rugae (Fig. 14, right); widely distributed

16

 * Mesosoma of queen wider than head (Plate 17 A and B); common and widely distributed from western USA to southern México Crematogaster coarctata
 * Mesosoma of queen narrower than head (Plate 54 A and B); rarely collected, Utah west to southern California, south to southern México Crematogaster mutans
 * Note: Unfortunately, we have not been able to find consistent characters to separate the workers of these two species, but Crematogaster coarctata is very common, Crematogaster mutans is rarely collected.

17

 * Dorsum of head with more than 10 erect hairs, dorsum of mesosoma with more than 15 erect hairs (Fig. 15 right)
 * Dorsum of head usually with fewer than 10 erect hairs, dorsum of mesosoma usually with fewer than 15 (up to 20 may be present) short bristle-like erect hairs (Fig. 15, left); California east to SE Canada S to Florida and northern Mexico Crematogaster lineolata

18

 * Most of dorsum of head smooth and glossy, surrounding area finely striolate or areolate (Fig. 16 and 17)
 * Dorsum of head nearly completely punctate (see Fig. 8, left), medial area may be glossy

19

 * Most hairs on pronotal shoulder relatively short (less than 0.15 mm) (Fig. 16); Texas northeast to New Jersey, south to Florida Crematogaster pilosa
 * Most hairs on pronotal shoulder relatively long (over 0.18 mm in length) (Fig. 15, right); Nevada, Colorado, Arizona and New Mexico Crematogaster navajoa

20

 * Longitudinal carina well developed in center of pronotum; southern half of the US south to central México Crematogaster punctulata
 * Longitudinal carina poorly developed on center of pronotum; eastern and central México Crematogaster patei

21

 * Dorsum of head (face) partially smooth and glossy (Fig. 18, left); México south to Argentina Crematogaster distans
 * Dorsum of head predominantly or completely and densely punctate or vermiculate, dull (Fig. 18, right)

22

 * Propodeal spines nearly as long or longer than width of petiole (Fig. 19, left); México to Brazil
 * Propodeal spine length much less than ½ width of petiole (Fig. 19, right); southern Texas to Costa Rica

23
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 * Dorsum of head and pronotum densely punctate (Fig. 20, left); México and Guatemala Crematogaster formosa
 * Dorsum of head and pronotum roughly rugose punctate or vermiculate punctate (Fig. 20, right); southern México south to Brazil Crematogaster acuta

24

 * Petiole elongate, almost 2X as long as wide (dorsal view), sides nearly parallel and straight (Fig. 2, right); propodeal spines reduced to tiny, sharp tooth; eastern and southern México to Brazil Crematogaster montezumia
 * Petiole subquadrate, slightly wider than long, widest medially (Fig. 19, right); propodeal spines well developed but small (length about 2X diameter of propodeal spiracle); southern USA (southern tip of Texas) to Costa Rica Crematogaster corvina

25

 * Petiole slender, 1.5-2 times as long as wide, slightly wider posteriorly, as seen from above (Fig. 21, left)
 * Petiole subquadrate (Fig. 21, right)

26

 * Dorsum of pronotum, including medial area, with several varicose or reticulate longitudinal carinae, which strongly contrast against smooth and shiny background (Fig. 22, left)
 * Dorsum of pronotum shiny, without carinulae at least medially, but carinulae may be present along edges (Fig. 22, right)

27

 * Propodeal spines very long, longer than length of distance between bases (measured from posterior edge of propodeal spiracle, seen from above), extending to near posterior edge of petiole (when petiole is in same plane as mesosoma) (see Fig. 23), diverging as seen from above; pronotum with long (longer than greatest eye diameter) dark brown or bronze colored hairs; southern Mexico south to Bolivia Crematogaster nigropilosa
 * Propodeal spines about as long as distance between bases when measure as above, slightly incurved (Fig. 22, left); pronotum with shorter (most about greatest eye diameter) silver or white hairs; Florida and México to Brazil Crematogaster curvispinosa

28

 * Clypeus completely smooth and glossy, occasionally with poorly developed longitudinal carinulae; hairs on pronotum dark brown; posterior edge of mesonotum with small angle (Fig. 23, left); USA (southern Arizona) to Bolivia Crematogaster sotobosque
 * Clypeus usually with moderately well-defined longitudinal carinulae; hairs on pronotum whitish; mesonotum without small angle (Fig. 23, right); México to Brazil Crematogaster limata

29

 * Dark brown (Fig. 24, left)
 * Yellow or pale brown (Fig. 24, right)

30

 * Lateropronotum mostly or entirely covered by horizontal striolae, usually mixed with punctures, weakly to moderately shining (Fig. 25, left); rarely collected, central México to Argentina Crematogaster atra
 * Lateropronotum predominantly smooth and glossy, strongly shining (Fig. 25, right); common and widely distributed

31

 * Most of clypeus (at least medial area) smooth and glossy (Fig. 26, left); southern Texas, Louisiana and southern Florida south to Venezuela Crematogaster obscurata
 * Clypeus covered with fine longitudinal striae (medial area may be slightly smooth and shining) (Fig. 26, right); widely distributed

32

 * Sternopetiolar process absent to poorly developed (Fig. 27, left); SW USA to Brazil Crematogaster torosa
 * Sternopetiolar process well developed (Fig. 27, middle); widely distributed including SW USA and México

33

 * Gaster sparsely evenly covered with short erect hairs (Fig. 28, left); sternopetiolar process small (Fig. 27, middle); SW USA to Argentina Crematogaster crinosa
 * Gaster without erect hairs except along lateral margins (Fig. 28, right); sternopetiolar process well developed (Fig. 27, right); México south to Brazil Crematogaster rochai

34

 * Erect hairs on pronotum very long, usually at least one hair longer than twice greatest eye diameter (Fig. 29. left); México to Argentina Crematogaster sumichrasti
 * Erect hairs on pronotum shorter than 1.5 times maximum eye diameter (Fig. 29, right); United States to Costa Rica

35

 * Propodeal spines relatively long (Fig. 30, left) as seen from above, length (measured from posterior edge of propodeal spiracle to tip) about ½ length of distance between bases (seen obliquely from above), and slightly bent upwards; carinulae on pronotal dorsum mostly on sides; middle and eastern USA to southern México; possibly Cuba Crematogaster missouriensis
 * Propodeal spines relatively short (Fig. 30, right), length less than ⅓ distance between bases, and not noticeably bent upwards; carinulae on pronotal dorsum also found in central region; S and SE USA to Costa Rica Crematogaster minutissima