Key to western US Crematogaster

This worker key is based on: Buren, W. F. 1968. A review of the species of Crematogaster, sensu stricto, in North America (Hymenoptera, Formicidae). Part II. Descriptions of new species. Journal of the Georgia Entomological Society. 3:91-121.

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1

 * Anterio-ventral tooth of petiole strikingly large; pubescence very long, appressed, and silky in appearance on all surfaces; post petiole trapezoidal, wider in front, and with straight sides; Nevada, and mountain-regions of California and probably Baja California at moderate altitudes; only North American species definitely suspected of being parasitic because of small female with compressed thorax, depressed gaster, and long, silky, appressed, yellowish pubescence . . . . . Crematogaster mutans


 * Without this combination of characters; anterio-ventral tooth of petiole usually normal in size or absent; postpetiole usually with convex sides, or if straight, wider behind than in front; females with normally developed thorax and gaster . . . . . 2

2
return to couplet #1
 * Erect hairs numerous on most of the dorsal surfaces of thorax and gaster; thorax punctate . . . . . 3


 * Erect hairs in various confined patterns on thorax and gaster but not numerous on entire dorsal surfaces; if the thorax is punctate, then erect hairs usually sparse or absent on thorax . . . . . 4

3
return to couplet #2
 * Pubescence long and suberect on head and thorax; thoracic puncturation fine, the surface subshining to subopaque; northern Arizona and New Mexico at moderate elevations under rocks and at bases of various plants . . . . . Crematogaster navajoa


 * Pubescence appressed and rather short on all surfaces; puncturation of thorax strong, the surface subopaque to opaque; abundant in southern Great Plains area, less numerous but well distributed through the southeastern states, and south into Mexico, and west to Arizona . . . . . Crematogaster lineolata

4
return to couplet #3
 * Declivity of epinotum and entire head strongly punctate; erect hairs numerous on gaster; western Mexico and southern Arizona in a number of habitats . . . . . Crematogaster dentinodis


 * Without this combination of characters . . . . . 5

5
return to couplet #4
 * Meso-epinotal impression deep but narrow; epinotum with long base, convex at sides when seen from above, the bases of the spines not inserted at the widest portion; arboreal in oaks in the mountain ranges of southern Arizona, New Mexico, and west Texas, and probably in northern Mexico . . . . . Crematogaster isolata


 * Without this combination of characters; the spines arising from the widest portion of the epinotum . . . . . 6

6
return to couplet #5
 * Thorax densely punctate; erect hairs of thorax restricted to a single hair on each pronotal shoulder or else entirely absent . . . . . 7


 * Thorax either with some other type of sculpture or else two or more erect hairs present on each pronotal shoulder . . . . . 12

7
return to couplet #6
 * Thorax devoid of erect hairs . . . . . 8


 * An erect hair present on each pronotal shoulder . . . . . 9

8
return to couplet #7
 * Head and thorax reddish in color; nests in and among roots and lower stems of various plants throughout the deserts and semi-desert regions of the southwest and northern Mexico . . . . . Crematogaster depilis


 * Head and thorax black or dark brown; restricted entirely as far as known to nesting in lower stems and among roots of the desert plant Larrea divaricata, the creosote bush, range probably co-extensive with that plant in Chihuahuan and Sonoran deserts both in the U. S. and in Mexico . . . . . Crematogaster larreae

9
return to couplet #7
 * Scapes longer than head length, thickest portion of scapes a little before the apex, the apex slighqy more slender; hemilobes of postpetiole rather sharply angulate behind in profile; mountains of New Mexico, Arizona, and west Texas under rocks at about 5,000 to 7,500 feet altitudes . . . . . Crematogaster colei


 * Scapes usually shorter than head length and with apices the thickest portion; post petiole usually not sharply angulate in profile behind . . . . . 10

10
return to couplet #9
 * Pubescent hairs suberect on scapes and head, rather long on body; apparently restricted to southern California and Baja California, found at bases and on roots of various plants cultivating aphids and coccids . . . . . Crematogaster californica


 * Pubescent hairs appressed on scapes and head and shorter and less noticeable on all surfaces, occuring only to the east of the Mojave and Colorado deserts . . . . . 11

11
return to couplet #10
 * Thorax opaque with strong puncturing on all surfaces except the epinotal declivity, may be found principally at bases and foraging on Opuntia fulgida, the chain fruit cholla cactus, and at bases of various other plants in the Sonoran desert of southern Arizona and surrounding semidesert . . . . . Crematogaster opuntiae


 * Thorax subshining, the puncturing very shallow except on lower mesopleura; imperfectly known from northern Arizona and southern Utah . . . . . Crematogaster nocturna

12
return to couplet #6
 * Distinct striae present on lower mesopleura . . . . . 13


 * Lower mesopleura without striae . . . . . 15

13
return to couplet #12


 * Scapes not or scarcely surpassing hind corners of head in larger specimens, without noticeable mesonotal declivity, thorax weakly punctate; a rather small, arboreal species restricted as far as known to manzanita and live oaks in California . . . . . . Crematogaster marioni


 * Scapes surpassing hind corners of head by one or two diameters; mesonotal declivity abrupt and angular; larger, ground inhabiting species . . . . . 14

14
return to couplet #13
 * Head entirely stria to-punctate; hills and mountains of California coastal area with one record from Nevada, suspected of now possibly being a rather rare species due to displacement by the Argentine ant . . . . . Crematogaster coarctata


 * Head smooth and shining behind the eyes or with weak striae there only, under rocks in desert regions of Idaho, Utah, Nevada, and hills and mountains of California and Baja California . . . . . Crematogaster mormonum

15
return to couplet #12
 * Head and thorax reddish; thorax shining but with fine distinct longitudinal striae; without distinct declivity at rear of mesonotum; usually arboreal in cottonwood trees along rivers and streams throughout west from Chihuahua and west Texas to California . . . . . Crematogaster hespera


 * Without this combination of characters . . . . . 16

16
return to couplet #15
 * Thoracic hairs short and straight, in a clump of 4 to 6 or more on each pronotal shoulder plus one or two pairs at rear of mesonotum; often constructs carton structures under rocks ; mountains of Colorado, Utah, Arizona, New Mexico, western Texas, and northern Mexico . . . . . Crematogaster emeryana


 * Thoracic hairs long and flexuous, confined to one to three hairs on each pronotal shoulder, rest of thorax devoid of hairs . . . . . 17

17
return to couplet #16
 * Spines very short, straight, or slightly to moderately incurved; petiole narrow, scarcely wider than the postpetiole; mountains of west Texas, southern New Mexico, and southern Arizona at altitudes usually over 5,000 ft., suspected of being widely distributed also in mountains of Chihuahua and Sonora, Mexico . . . . . Crematogaster browni


 * Spines divergent, sinuate, sometimes with outwardly curved tips; petiole broadly trapezoidal; occurs in northern New Mexico and rest of range as given in key A, but probably never sympatric with the preceding species . . . . . Crematogaster cerasi