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 90° (right) angle; there is often a thick lamina or other outgrowth on the dorsal surface of the bend	 . . . . . 11

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


 * 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

3
return to couplet #2
 * Clypeus deeply and distinctly notched; propodeal spines long and pointed rearward at an ~45° angle and with tips that curve gently downward; a bog specialist	M. lobifrons


 * 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

4
return to couplet #2
 * 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


 * 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

5
return to couplet #4
 * Propodeal spines short with thickened base; large triangular process visible below the petiole; a temporary social parasite of M. punctiventris	            M. semiparasitica


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

6
return to couplet #5


 * 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


 * 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

7
return to couplet #4
 * 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


 * 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

8
return to couplet #7
 * 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


 * 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

9
return to couplet #8


 * 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


 * 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

10
return to couplet #8


 * Process below the petiole conical and angular; ant shiny, with virtually no sculpturing; an inquiline social parasite of M. alaskensis                   M. lampra


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

11
return to couplet #1
 * 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


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

12
return to couplet #11
 * 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


 * 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

13
return to couplet #12


 * 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


 * 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

14
return to couplet #12
 * 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


 * 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

15
return to couplet #14


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


 * Propodeum with spines, all castes present	 . . . . . 16

16
return to couplet #15


 * 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


 * 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

17
return to couplet #16
 * 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


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

18
return to couplet #14
 * Lower surface of post-petiole is lobed and projecting forward when viewed in profile	M. latifrons


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

19
return to couplet #18


 * 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


 * 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

20
return to couplet #19


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


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