Key to Myrmica of North America

This key to North American species of Myrmica is a work-in-progress and should be used as a guide only. This group is in serious need of taxonomic work and this key is a small contrubution to this effort.

1

 * Node of petiole high, distinctly set off from anterior and posterior peduncles and angular at crest; ventral surface of petiole with distinct, obtusely angular impression formed by the junction of the anterior and posterior peduncles; Arizona Myrmica wheeleri
 * Node of petiole not distinctly set off from anterior and posterior peduncles or, if so, it is low and much rounded above; ventral surface of petiole straight or very feebly convex

2

 * Outer edge of frontal lobe feebly convex throughout most of its length and fusing with head without marked posterior incision; frontal area distinct, not crossed by rugae, usually smooth and strongly shining; Quebec, Maine, Massachusetts, Rhode Island Myrmica rubra,  Myrmica rubra neolaevinodis
 * Outer edge of frontal lobe strongly convex or angular in front, or deeply incised behind, or both; frontal area obscured by rugae, never completely smooth and shining (except in M. punctiventris)

3

 * Frontal lobes narrow, scarcely or not at all projecting above antennal fossae; insertions of antennae exposed when head is viewed from above; Tennessee, Mississippi, Illinois Myrmica spatulata
 * Frontal lobes strongly projecting out over antennal fossae; insertions of antennae hidden when head is viewed from above

4

 * Antennal scape evenly curved at base, upper surface never forming right angle at bend (sometimes about 80°); lamina, if present, low and inconspicuous
 * Antennal scape sharply bent at base, upper surface forming right angle or nearly so; lamina always present, of varying shapes

5

 * Lateral portion of clypeus raised into carina which forms abrupt, semi-circular boundary at front of antennal fossa (as in Tetramorium) Myrmica rugiventris
 * Clypeus not as above

6A

 * Frontal area mostly smooth and glossy and with at most 1 or 2 short posterior rugae which are less than half the length of the frontal area
 * Frontal area roughly sculptured, with several rugae which extend at least 1/2 its length

6B

 * First gastric segment without coarse, large punctures; propodeal spines elongated with a narrow, thin base; California Myrmica punctinops
 * First gastric segment with coarse, large piliferous punctures; propodeal spines short and dentiform with a large, thick base; eastern North America Myrmica semiparasitica

6

 * Basal face of propodum abruptly depressed below level of mesonotum; gaster with numerous coarse punctures with diameters at least 5X diameter of hairs arising from them
 * Basal face of propodium forming descending slope at about level of mesonotum, which is separated from mesonotum only by impression at metanotal suture; gaster with fine punctures, whose diameter is less than 3X diameters of hairs

7

 * Antennal scapes surpassing occipital margin by an amount equal to their greatest thickness; propodeal spines about 1½ X as long as distance which separates their bases and slightly deflected downward; color piceous brown; length 4.0-4.7 mm; antennal scape of male as long as following 6 segments together; Massachusetts to Georgia to Iowa, Nebraska, Arkansas, Texas Myrmica punctiventris
 * Antennal scapes barely surpassing occipital margin; propodeal spines only slightly longer than distance which separates bases, not deflected downward; color brownish yellow; length 3.5-4.0 mm; antennal scape of male as long as following two segments together; Massachusetts to South Carolina, west to Ohio, Oklahoma, Mississippi Myrmica pinetorum

8

 * Gaster with longitudinal striae extending about 2/3 length of first gastral tergum, sparsely, but distinctly; punctate; inquiline in nest of Myrmica striolagaster; Texas (Davis Mts.) Myrmica colax
 * Gaster without longitudinal striae

9

 * Lateral margins of frontal lobes strongly angular, thick and slightly, but definitely deflected downward; antennal scapes of male not longer than 3 following segments together and straight at base)
 * Lateral margins of frontal lobes rounded, thin and moderately to strongly elevated; antennal scape of male varies in length
 * Note contradiction in length of antennal scape in 9 and 10

10

 * Antennal scape of male slightly bent at base and as long as following 4 or 5 segments together; common
 * Antennal scape of male straight at base and shorter than following 3 segments; New Mexico; rarely collected Myrmica species "B"

11

 * Postpetiole with shining dorsal area that is largely free from rugae; average size of workers 3.5 mm; Alaska, Quebec Myrmica alaskensis
 * Postpetiole ordinarily covered with rugae, rarely with dorsal area free from rugae, but in such cases this area is not shining; average size of workers at least 4.5 mm; Labrador south to New Jersey, west to Rocky Mountains, Wyoming, New Mexico

12

 * Sculpture fine, color reddish-brown over most of body and appendages Myrmica incompleta
 * Sculpture of head and mesosoma coarse; color dark brownish-black to black, legs, mesosoma and antennae lighter Myrmica whymperi

13

 * Color often orange-yellow, but variable; propodeal spines slightly less than one-half as long as distance which separates tips; North Dakota, Nebraska to New Mexico, west to Alberta, Idaho Myrmica brevispinosa
 * Color dark brown; propodeal spines more than ½ as long as distance which separates tips

14

 * Antennal scape of male approximately as long as 5 funicular segments (Fig.); area between lateral ocellus and eye of male mostly punctate; Newfoundland to mountains of Colorado, Wyoming, New Mexico Myrmica discontinua
 * Antennal scape of male approximately as long as 7 funicular segments (Fig.); area between lateral ocellus and eye mostly with reticulate rugae; eastern Mexico (Nuevo Leon, Coahuila south to Veracruz) Myrmica mexicana

15

 * Bend of antennal scape with large, thick, lobose lamina that extends backward along basal third of scape; Quebec, Michigan to Manitoba, North Dakota, Colorado
 * Bend of antennal scape with small transverse lamina or with thin lamina which surrounds bend like collar and does not extend backward along basal third of scape

16

 * Myrmica monticola
 * Myrmica nearctica

17

 * Scape covered with longitudinal rugae; gaster with longitudinal striae on first tergum, obvious at least near point of attachment of post petiole (gradient exists with less developed striae in western populations); gaster with coarse punctures with diameters about 5X diameter of hairs; Arizona (Chiricahua Mountains), New Mexico (entire state), West Texas, Chihuahua (entire state), Colorado Myrmica striolagaster
 * Scape usually with fine sculpture, mostly punctate; gaster without striae and with punctures whose diameter is less than 3X diameter of hairs

18

 * Ventral surface of postpetiole seen in profile flat or nearly so and not forming anterior projection; antennal scapes of male as long or longer than following 4 segments together and straight at base; Quebec, Maine to North Carolina, Tennessee to Manitoba, Colorado, Utah, Arizona Myrmica americana
 * Ventral surface of postpetiole seen in profile convex or forming prominent anterior projection that thrusts forward under anterior peduncle; antennal scapes of male bent at base, or if straight they are distinctly shorter than above

19

 * Lamina of antennal scape forming high, semicircular welt that surrounds scape at bend; antennal scape of male bent at base and usually shorter, never longer, than 3 following segments taken together
 * Lamina of antennal scape not forming high, semicircular welt; antennal scape of male straight at base or if bent, its length is equal to following 5 segments together

20

 * Area of scape immediately distal to flange with carina (Fig.), which often joins flange (Fig.); scape of male about equal in length to first 3 segments of funiculus; widely distributed
 * Area of scape immediately distal to flange without carina or with carina very weakly developed; scape of male greater in length than following 7 segments

20A

 * Nevada, Colorado Myrmica wheelerorum
 * Arizona Myrmica species "mag"
 * New Mexico Myrmica species "A"

21

 * Lamina of antennal scape under-cut on inner face, edge forms distinct hook (Fig. ); Colorado, New Mexico, Arizona, Utah Myrmica hamulata
 * Lamina of antennal scape without hook on inner face; Iowa

21A

 * Body smaller; dorsal surface of petiolar node rounding into posterior face, the separation minimal or absent Myrmica crassirugis
 * Body larger; dorsal surface of petiolar node separated from posterior face by an angle

21B

 * Small flange extending distally along scape from collar at antennal bend; postpetiole in profile asymetrical, anterior face inclined posteriorly compared to posterior face; New Mexico Myrmica SPC#19
 * Collar at antennal bend transverse, not extending distally along scape; postpetiole in profile more or less symetrical, anterior and posterior faces similarly shaped; Iowa Myrmica trullicornis

22

 * Lamina of antennal scape small and diagonally transverse on upper surface of scape, but continued as prominent transparent flange along inner surface of that part of scape that lies below bend; antennal scape of male straight at base and as long as 3 following segments taken together)
 * Lamina not forming prominent median flange as above or if small median flange is present, lamina not transverse on the upper surface of scape

22A

 * Lamina of antennal scape more extensive, extending slightly distally of and beyond bend
 * Lamina less extensive, ending at or just before bend; Newfoundland to Georgia west to Manitoba, Idaho, Colorado, Arizona Myrmica latifrons

22B

 * Sculpture on dorsal surface of postpetiole weakly developed medailly, more strongly developed laterally; widespread Myrmica detritinodis
 * Sculpture on dorsal surface of postpetiole uniformly developed across entire width

22C

 * Body smaller; promesonotum uniformly convex; dorsal surface of propodeum uniformly convex; interrugal sculpturing on head weakly developed and more shiny, especially posterior of antennal insertion; North Carolina, Massachusetts, Illinois, Maine, Michigan, D.C., New Jersey, New York, Missouri, Indiana, Georgia, Iowa, Connecticut Myrmica species "smitha"
 * Body larger; promesonotum strongly convex anteriroly (immediately posterior of collar) and weakly convex posteriorly (along the dorsal surface); dorsal surface of propodeum more strongly arched anteriorly, weakly convex to nearly flat posteriorly; interrugal sculpturing on head well developed and less shiny, especially posterior of antennal insertion; Massachusetts, Maine, New York Myrmica species "sculp"

23

 * Propodal spines slightly, but distinctly bent downward (spines on single ant may be different); mesosoma reddish-yellow, head and gaster piceous; antennal scape of male straight at base and as long as following 3 segments together; Montana, Wyoming, Utah, Arizona to British Columbia, Nevada, Oregon Myrmica tahoensis
 * Propodal spines straight; color not as above; antennal scape of male bent at base and at least as long as following 5 segments together

24

 * Antennal lamina encircling bend of scape in form of spoon-like or saucer-like flange; antennal scape of male abruptly bent at base with upper surface distinctly angulate at bend; propodal spines of male well-developed, propodeum with prominent rugae; CO, NM, UT, AZ, N to Alaska Myrmica lobifrons
 * Antennal lamina small, transverse, forming angular tooth-like projection on inner side of bend; antennal scape of male gradually bent at base and not forming distinct angle at bend; propodal spines of male reduced to rounded angles, rugae of propodeum very feeble or lacking; Newfoundland south to Tennessee, Ohio, west to Rocky Mountains, Colorado, New Mexico, Utah, Arizona Myrmica fracticornis