Key to New England Myrmica

This key is modified from the 2012 book A Field Guide to the Ants of New England.

Related pages:
 * New England Ant Species
 * New England Ant Identification

1

 * Antennal scape viewed in full profile is evenly curved near its base	2


 * Antennal scape viewed in full profile is bent abruptly near its base at a nearly 90o (right) angle; there is often a thick lamina or other outgrowth on the dorsal surface of the bend	11

2a (1a). Anterior margin of clypeus distinctly notched; if notch is shallow, propodeal spines are short	(lobifrons group) 3

2b. Anterior margin of clypeus usually without a notch; if a very shallow notch is present, the clypeus bulges outward in the middle and the propodeal spines are long	4

3a (2a). Clypeus deeply and distinctly notched; propodeal spines long and pointed rearward at an ~45o angle and with tips that curve gently downward; a bog specialist	M. lobifrons

3b. Clypeus shallowly notched; propodeal spines short and pointing straight upward; a boreal species known in New England only from White Mountains of New Hampshire	M. brevispinosa

4a (2b). Coarse, large punctures (pits) at the base of the erect hairs on the top of the gaster; level of propodeum noticeably lower than the level of the promesonotum (punctiventris group) 5

4b. No, or at best fine, inconspicuous punctures at the base of the erect hairs on the top of the gaster; level of propodeum more or less even with the level of the promesonotum	7

5a (4a). Propodeal spines short with thickened base; large triangular process visible below the petiole; a temporary social parasite of M. punctiventris M. semiparasitica

5b. Propodeal spines long with narrow base; triangular process below the petiole inconspicuous	6

6a (5b). Propodeal spines longer than the distance separating their tips and often wavy; frontal lobes extend upward at a shallow angle, exposing the insertion of the antennae; rugae thick, but flattened on top 	M. punctiventris

6b. Propodeal spines shorter than the distance separating their tips and usually straight; frontal lobes flat to the head, often with a distinct downward deflection at their edges, and covering the insertion of the antennae; rugae thick and rounded on top	M. pinetorum

7a (4b). Viewed from above, frontal lobes thin, and pointed upwards, exposing the insertion of the antennae; clypeal margin with small indentations; an introduced Palearctic species common along coasts and rivers, as well as in urban disturbed areas	M. rubra

7b. Viewed from above, frontal lobes thick and laterally extended, at least partially covering the insertion of the antennae; clypeal margin entire, without small indentations	 (incompleta group) 8

8a (7b). Head, clypeus, mesosoma, and petiole heavily sculptured and striated; lower surface of petiole with at most a small outgrowth or process; top of post-petiole in side view evenly (straight) sloped	9

8b. Ant weakly sculptured, if at all; lower surface of petiole with a large, process; top of post-petiole hump-shaped in profile; inquiline social parasites; if workers are present, they lack the process under the petiole and instead are workers of the host species	10

9a (8a). Ant of deciduous forests; clypeus bulges in the middle and straight or modestly concave on the margin; rugae on top of the head anastomosing and net-like	M. incompleta

9b. Ant of boreal forests; clypeus evenly convex in the middle and distinctly convex on the margin; rugae on top of the head parallel M. alaskensis

10a. (8b) Process below the petiole conical and angular; ant shiny, with virtually no sculpturing; an inquiline social parasite of M. alaskensis M. lampra

10b. Process below the petiole large, rectangular, and blunt; not very shiny, with light sculpturing; an inquiline social parasite of M. alaskensis	M. quebecensis

11a (1b). Antennal scape tapered on both sides, giving it a ridge on top and a triangular appearance in cross-section; a Palearctic, non-native species M. scabrinodis

11b. Antennal scape not tapered, giving it a rounded shape in cross-section; Nearctic, native species	12

12a (11b). Mesosoma, petiole, and post-petiole with thick, parallel, rugae that would appear round in cross-section; in full-face view, lateral wings of clypeus extended and raised anteriorly into a ridge that encloses the antennal socket; in dorsal view, lamella on the antennal bend are most apparent on the interior side, not on top, of the bend (sculptilis group) 13 12b. Mesosoma, petiole, and post-petiole with thinner, net-like, anastomosing rugae that would appear sharply-angled in cross-section; in full-face view, lateral wings of the clypeus usually not raised anteriorly into a ridge that encloses the antennal socket; but if the clypeal wings are raised and enclose the antennal socket, then the lamella on the top of the antennal bend, in dorsal view, is apparent and well developed	14

13a (12a). In full-face view, frontal lobes large and rounded, covering the antennal socket; in dorsal view, antennal scape with a small outgrowth/lamella that is not wider than the base itself and with a ridge running along the inside of the base (towards the head)	Myrmica sp. AF-scu

13b. Frontal lobes smaller and with a convex margin, not covering the antennal socket; margin of the frontal lobes may have two separate ridges; in dorsal view, the lamella on the base of the scape is wider than the base itself Myrmica sp. AF-smi

14a (12b). In dorsal view, the shaft of the antennal scape is distinctly narrower at the bend than it is at its apex; the lamina on the dorsal part of the antennal bend may extend downwards towards the head, but never extends along the scape itself	 (detritinodis group) 15

14b. In dorsal view, the shaft of the antennal scape is more or less uniformly wide across its entire length; the lamina on the dorsal part of the scape does not extend downwards towards the head, but may extend anteriorly along the scape itself	18

15a (14a). Propodeum without spines; rugae create a spider-web pattern on the head, and anastomosing rugae on the sides	Myrmica sp. AF-ine

15b. Propodeum with spines, all castes present	16

16a (15b). In dorsal view, the bend of the antennal scape has a curved or transverse lamina that continues downwards along the inner side of the base (towards the head). Forested habitats M. detritinodis

16b. In dorsal view, the lamina at the bend of the antennal scape is restricted to the top of the scape and does not run downwards along the base of the antenna; open and forest-edge habitats	17

17a (16b). In dorsal view, the lamina at the bend of the scape is small and barely visible; a widespread ant of open habitats in northern New England	M. fracticornis

17b. In dorsal view, the lamina at the bend of the scape is large and conspicuous; an uncommon, boreal species	Myrmica sp. AF-sub

18a (14b). Lower surface of post-petiole is lobed and projecting forward when viewed in profile	M. latifrons

18b. Lower surface of post-petiole is flat; in profile, post-petiole is slightly convex, but not lobed	 (nearctica group) 19

19a (18b). In full-face view, lateral wings of clypeus are raised into a ridge that encloses the antennal socket; margin of frontal lobes are evenly rounded over most of their length; in dorsal view, lamella at antennal bend is spoon-shaped, not extending along the inner (posterior) side of the scape towards its apex	20

19b. In full-face view, lateral wings of clypeus flattened and not enclosing the antennal socket; margin of frontal lobes rounded towards the front but straight or convex posteriorly; in dorsal view, lamella at antennal bend large, and the lamina extends along the inner margin of the scape anteriorally towards its apex	M. nearctica

20a (19b). In dorsal view, the bend of the antennal scape has a large, circular, spoon-like lamella that projects sharply upward M. americana

20b. In dorsal view, the bend of antennal scape with a smaller lamella that is barely deflected inwardly, giving it a shallow spoon-shape	M.yrmica sp. AF-eva