Key to Nearctic Formica fusca group queens

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This queen key is based on: Francoeur, A. 1973. Révision taxonomique des espèces néarctiques du groupe fusca, genre Formica (Formicidae, Hymenoptera). Mémoires de la Société entomologique du Québec. 3:1-316.

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1

  • Metasternum with two distinctly pilose processes, arising on each side of the spinasternal cavity (fig. 15, 42); mesometasternal profile composed of a convexity followed by an inverted triangle (fig. 33) . . . . . 2
  • Metasternum without such processes (fig. 195); mesometasternal profile composed of a convexity followed by a straight or concave line (fig. 34-35) . . . . . 10

2

return to couplet #1

  • Eyes smaller, ocular index usually less than 31; anterior border of median clypeal lobe distinctly angulate, i.e. formed of two straight sides meeting at midline to form an obtuse angle; dilute pubescence on gastric dorsum and on mesothoracic episterna; surface strongly shining; West of the continent . . . . . Formica subpolita
  • Eyes larger, ocular index greater than 31 (except pilicornis, but in this case erect hairs present on eyes); anterior border of the median clypeal lobe weakly angulate, i.e. formed of two convex sides meeting at the midline to form a wide angle, or completely convex or truncate; normal or dense pubescence on gastric dorsum and on mesothoracic episterna . . . . . 3

3

return to couplet #2

  • Body pilosity more abundant: in particular, erect hairs present on ventral surface of head, occiput, propodeum and covering more than the half of the surface on pronotum; sometimes absent on ventral surface of head of altipetens; present on genre, except for altipetens and usually except for montana; cinerea complex . . . . . 4
  • Body pilosity less abundant: in particular, erect hairs absent on genre, ventral surface of head, occiput (in most cases), propodeum and covering at most the posterior half on pronotum; neoclara complex . . . . . 8

4

return to couplet #3

5

return to couplet #4

  • Episterna without erect or suberect hairs; if a few ( 1 to 3) are present, these restricted to the peripheral margin of mesothoracic katepisterna; genre and usually occipital angles without erect hairs; sometimes absent on ventral surface of head; West of the continent . . . . . Formica altipetens
  • Episterna with erect or suberect hairs; genre with erect hairs (frequently absent on montana); occipital angles usually pilose . . . . . 6

6

return to couplet #5

  • Sides of head less pilose; head in full face view, erect hairs usually limited to occipital angles, but may be present down to ventral border of eyes; genre normally without erect hairs ,sometimes 1-2 near the tentorial fossae; occipital angles becoming glabrous in the western part of its range; eastern center of the continent . . . . . Formica montana
  • Sides of head more pilose; head in full face view, erect hairs present below ventral border of eyes; genre normally with more than 2 erect hairs . . . . . 7

7

return to couplet #6

  • Body yellowish to dark brown; density of pubescence normal to feeble surface slightly shining; ocular halo distinct and shining; punctures of frons clearly interspaced and readily seen; scapes shorter, scape index varying from 81 to 86; West and western center of the continent . . . . . Formica canadensis
  • Body blackish brown to black; pubescence very dense; surface opaque; without ocular halo; punctures of frons closed together and hard to locate; longer scapes, scape index more than 86; Mexico . . . . . Formica pulla

8

return to couplet #3

  • Body concolorous blackish brown or black; dorsal margin of petiole usually low and convex, sometimes slightly sinuate; South-west of the continent . . . . . Formica occulta
  • Bicolored body: deep brown and yellowish brown at least on thorax; margin of petiole low and sinuate or concave . . . . . 9

9

return to couplet #8

  • Erect hairs numerous ( > 15) on posterior margin of pronotum, lined on two rows or more, reaching the tegulae; dorsal margin of petiole sinuate but without a broad and deep median notch; sometimes few erect hairs on occiput and prosternum; Mexico . . . . . Formica propatula
  • Erect hairs less numerous ( < 15) on the posterior margin of pronotum, lined on one row, not reaching the tegulae (except probably in Idaho); dorsal margin of petiole more or less concave; from Yukon to Texas . . . . . Formica neoclara

10

return to couplet #1

  • Body concolorous: black, blackish or yellowish brown; if appearing bicolored, alitrunk partly yellow and very pilose or alitrunk partly reddish and the upper half of head black . . . . . 11
  • Body bicolored: head, alitrunk and petiole reddish or reddish brown, gaster black or blackish brown; surface opaque and granulose (except in F. gnava and F. foreliana, but then pubescence is dilute on genre and mesothoracic episterna); gastric pubescence dense on the first three tergites (except in the species cited); southern half of the continent; rufibarbis and occidua complexes . . . . . 28

11

return to couplet #10

  • The portion of the gena lying between the eye and the insertion of the mandible covered with coarse, elongate punctures, widely spaced in the posterior half of the gena (fig. 37); the surface between them with a microreticulum composed of coarse lines; pubescence dilute on mesothorax and at least on posterior half of gastric dorsum; metasternal pilosity abundant and surrounding the spinasternal cavity; neorufibarbis complex . . . . . 12
  • Genre without coarse, elongate punctures or if present, these punctures are mostly concentrated in the posterior half of the genre, where they are always mixed with fine circular punctures and are closely spaced; the surface between them with a microreticulum composed of delicate lines; pilosity and pubescence variously combined . . . . . 13

12

return to couplet #11

  • Body pilosity abundant: in particular, numerous on ventral surface of head, occiput posterior half of pronotum, prosternum, propodeum and dorsal margin of petiole; numerous (mean = 25) on the first gastric tergite exclusive of the posterior row; sometimes 1-3 hairs on genre, near the tentorial fossae; sometimes erect hairs absent on the ventral surface of head and dorsal margin of petiole . . . . . Formica hewitti
  • Body pilosity reduced: in particular, erect hairs absent on ventral surface of head, genre, occiput, prosternum, propodeum and dorsal margin of petiole; on an average less than 5 hairs on the first gastric tergite exclusive of the posterior row; limited to one row on posterior margin of pronotum; sometimes 1-3 hairs on occiput; pilosity of the toundra form similar to the one of hewitti but less abundant, differing by a propodeum always hairless, a reduced size (head width less than 1.58 mm) and a bicolored body . . . . . Formica neorufibarbis

10

return to couplet #1

  • Body concolorous: black, blackish or yellowish brown; if appearing bicolored, alitrunk partly yellow and very pilose or alitrunk partly reddish and the upper half of head black . . . . . 11
  • Body bicolored: head, alitrunk and petiole reddish or reddish brown, gaster black or blackish brown; surface opaque and granulose (except in F. gnava and F. foreliana, but then pubescence is dilute on genre and mesothoracic episterna); gastric pubescence dense on the first three tergites (except in the species cited); southern half of the continent; rufibarbis and occidua complexes . . . . . 28

11

return to couplet #10

  • The portion of the gena lying between the eye and the insertion of the mandible covered with coarse, elongate punctures, widely spaced in the posterior half of the gena (fig. 37); the surface between them with a microreticulum composed of coarse lines; pubescence dilute on mesothorax and at least on posterior half of gastric dorsum; metasternal pilosity abundant and surrounding the spinasternal cavity; neorufibarbis complex . . . . . 12
  • Genre without coarse, elongate punctures or if present, these punctures are mostly concentrated in the posterior half of the genre, where they are always mixed with fine circular punctures and are closely spaced; the surface between them with a microreticulum composed of delicate lines; pilosity and pubescence variously combined . . . . . 13

12

return to couplet #11

  • Body pilosity abundant: in particular, numerous on ventral surface of head, occiput posterior half of pronotum, prosternum, propodeum and dorsal margin of petiole; numerous (mean = 25) on the first gastric tergite exclusive of the posterior row; sometimes 1-3 hairs on genre, near the tentorial fossae; sometimes erect hairs absent on the ventral surface of head and dorsal margin of petiole . . . . . Formica hewitti
  • Body pilosity reduced: in particular, erect hairs absent on ventral surface of head, genre, occiput, prosternum, propodeum and dorsal margin of petiole; on an average less than 5 hairs on the first gastric tergite exclusive of the posterior row; limited to one row on posterior margin of pronotum; sometimes 1-3 hairs on occiput; pilosity of the toundra form similar to the one of hewitti but less abundant, differing by a propodeum always hairless, a reduced size (head width less than 1.58 mm) and a bicolored body . . . . . Formica neorufibarbis

13

return to couplet #11

  • Body pilosity abundant: in particular, erect hairs present on ventral surface of head and metafemora, occiput, propodeum (except in subcyanea, but then surface granulose and opaque) and petiolar tergite; numerous on pronotum and covering all its surface or nearly so; West and South on the continent . . . . . 14
  • Body pilosity reduced: in particular, erect hairs absent on propodeum, dorsal margin of petiole and at least on one or two or three of other mentioned structures; less numerous on pronotum and limited to posterior half . . . . . 20

14

return to couplet #13

  • Body concolorous black; polygons of microreticulum very small (type 3); surface opaque and granulose; erect hairs absent on propodeum; Mexico . . . . . Formica subcyanea
  • Body yellowish to blackish brown; alitrunk often lighter in color than head and gaster; surface feebly shining; erect hairs present on propodeum; West and South of the continent; lepida complex . . . . . 15

15

return to couplet #14

  • Erect or suberect hairs present on the four faces of femora; California. (Tentatively) . . . . . Formica lepida
  • Erect or suberect hairs limited to ventral and lateral faces of femora . . . . . 16

16

return to couplet #15

  • Episterna, occipital angles and gena: with numerous erect hairs . . . . . 17
  • Occipital angles and gena: hairless or nearly so; erect hairs, if present, limited to the periphery on mesothoracic episterna . . . . . 19

17

return to couplet #16

  • Dorsal margin of petiole high, angulate or angulo-convex, entire or with a minute notch in the middle; short scapes, scape length minus head length equal to - 0.29 mm, scape index 88; Mexico . . . . . Formica pachucana
  • Dorsal margin of petiole low, feebly convex or straight or sinuate, entire or notched; scape length varying . . . . . . 18

18

return to couplet #17

  • Head more elongate, cephalic index 96-100; scapes longer, scape length minus head length varying from - 0.31 to - 0.15 mm, scape index 85-94; length of longest pronotal hairs less than 1.3 X the height of frontal triangle; from British Columbia to California. . . . . Formica transmontanis
  • Head less elongate, cephalic index 100-105; scapes shorter, scape length minus head length varying from - 0.38 to - 0.28 mm, scape index 75-85; length of longest pronotal hairs more than 1.3 X the height of frontal triangle; California. (Tentatively) . . . . . Formica longipilosa

19

return to couplet #16

  • Head less elongate, cephalic index 100-l06; scapes shorter, scape length minus head length varying from - 0.37 to - 0.30 mm, scape index 79-83; anterior margin of clypeus convex; body pilosity more abundant . . . . . Formica aerata
  • Head more elongate, cephalic index 94-101; scapes longer, scape length minus head length varying from - 0.32 to - 0.21 mm, scape index 85-96; anterior margin of clypeus angulate; body pilosity less abundant . . . . . Formica pacifica

20

return to couplet #13

  • Surface more or less shining; punctures of frons coarser, readily seen under low magnification, interspaces large and shining (less evident on F. argentea because the pubescence is very dense); big elongate punctures beneath and behind the eyes (except on F. argentea); mesometasternum profile with a high, rather narrow convexity followed by an angle (fig. 34) . . . . . 21
  • Surface opaque and granulose; punctures of frons finer, difficult to locate under high magnification, interspaces very reduced, opaque or nearly so; without big elongate punctures beneath and behind the eyes; mesometasternum profile with a low and elongate convexity followed by a concavity (fig. 35); West of the continent; sibylla complex. (Tentatively) . . . . . 27

21

return to couplet #20

  • Katepisterna of mesothorax completely covered with normal or dense pubescence and punctation; metasternum less pilose, hairs not surrounding the spinasternal cavity and generally restricted behind it; subsericea complex . . . . . 22
  • Katepisterna of mesothorax with dilute pubescence and punctation, at least in the center; metasternum more pilose, hairs surrounding the spinasternal cavity; fusca complex . . . . . 25

22

return to couplet #21

  • Pubescence very dense particularly on genre and the first four gastric tergites; big elongate punctures absent on genre, beneath and behind the eyes; posterior margin of pronotum with numerous erect hairs, varying from 4 to 20 (mean = 11), usually reaching the tegulae . . . . . Formica argentea
  • Pubescence dilute to feebly dense on the first three gastric tergites, dilute on the fourth, partly dilute or normal on genre; big, elongate punctures present on genre, beneath and behind the eyes; pilosity varying . . . . . 23

23

return to couplet #22

  • Scapes longer, scape length more than 1.80 mm (fig. 251); occipital margin convex; pubescence normal on the first three gastric tergites; pilosity of pronotum limited to median half of posterior margin; erect hairs varying from 0 to 10 (mean = 2) on the first gastric tergite exclusive of the posterior row; larger species, alitrunk length from 3.55 to 4.25 mm (mean = 3.90); wings blackish; East of the continent . . . . . Formica subsericea
  • Scapes shorter, head length less than 1.80 mm (fig. 251, 270); occipital margin straight or slightly convex; pubescence and pilosity differently combined; smaller species, alitrunk length varying from 2.95 to 3.73 mm (mean= 3.37 mm); wings usually paler . . . . . 24

24

return to couplet #23

  • Body pilosity less abundant, particularly on pronotum, profemora and the first gastric tergite; erect hairs of pronotum varying from 5 to 16 (mean = 9), usually lined on one row in the median half of posterior margin and not reaching the tegulae; from 0 to 7 (mean = 3) erect hairs on the first gastric tergite exclusive of the posterior row; pubescence of gastric dorsum dilute at least from the third tergite; East of the continent . . . . . Formica glacialis
  • Body pilosity more abundant, particularly on pronotum, profemora and first gastric tergite; erect hairs of pronotum varying from 12 to 29 (mean = 18), lined on more than one row and usually reaching the tegulae; from 0 to 14 (mean = 6) erect hairs on the first gastric tergite exclusive of the posterior row; sometimes 1-3 hairs on occiput, ventral surface of head and prosternum; pubescence dense, sometimes normal, on the first three gastric tergites, dilute on the others . . . . . Formica podzolica

25

return to couplet #21

  • Eyes smaller, ocular index 28-32; antero-paracarinal setae longer than 0.42 X the length of clypeus; head more quadrate, convergence index, less than 19; California. (Tentatively) . . . . . Formica microphthalma
  • Eyes larger, ocular index 31-38; antero-paracarinal setae shorter than 0.42 X the length of clypeus; head more trapezoidal, convergence index 19-30 (mean = 23) . . . . . 26

26

return to couplet #25

  • Scapes longer, length varying from 1.69 to 1.98 mm, mean = 1.85 mm (fig. 361); anteror margin of clypeus usually angulate; antero-paracarinal setae of clypeus usually longer than the height of frontal triangle; gastric pubescence normal on the first three tergites, sometimes partly dilute on the third; larger species, alitrunk length 3.25 - 3.90 mm; West of the continent . . . . . Formica accreta
  • Scapes shorter, length varying from 1.35 to 1.75 mm, mean = 1.58 mm (fig. 361); anterior margin of clypeus angulo-convex or convex; anteroparacarinal setae of clypeus usually shorter than the height of frontal triangle; gastric pubescence dilute at least from the second tergite; smaller species, alitrunk length 2.60 - 3.50 mm . . . . . Formica fusca

27

return to couplet #20

  • Erect hairs present on ventral surface of head and prosternum; head rectangular; antero-paracarinal setae of clypeus longer; eyes smaller. (Tentatively) . . . . . Formica sibylla
  • Erect hairs absent on ventral surface of head and prosternum; head weakly trapezoidal; antero-paracarinal setae of clypeus shorter; eyes larger; California. (Tentatively) . . . . . Formica subelongata

28

return to couplet #10

  • Surface shining and shagreened or opaque and granulose; microreticulum of type 2 or 3; gastric pubescence dense, normal or dilute on the first three tergites, dilute at least in part on the fourth; mesometasternal profile with a high, more or less narrow convexity followed by an angle (fig. 34); metasternal pilosity surrounding in part the spinasternal cavity; lateral margin of eyes not reaching the margin of head viewed in full face; rufibarbis complex . . . . . 29
  • Surface opaque and granulose with a microreticulum of type 3; gastric pubescence dense on tergites 1 to 4; episterna of mesothorax with dense pubescence; mesometasternal profile with a low and elongate convexity followed by a concavity (fig. 35); metasternal pilosity not surrounding the spinasternal cavity; ventral half of the lateral margin of eyes projecting beyond the margin of head viewed in full face; occidua complex . . . . . 32

29

return to couplet #28

  • Surface opaque and granulose with a microreticulum of type 3; katepisterna of mesothorax completely covered with dense pubescence and punctation; head usually larger than thorax, head width minus thorax width varying from - 0.04 to + 0.80 mm. Mexico . . . . . 30
  • Surface shining and shagreened with a microreticulum of type 2; katepisterna of mesothorax with dilute pubescence and punctation at least on two thirds of their surface; head usually narrower than thorax, head width minus thorax width varying from - 0.32 to - 0.10 mm. Mexico and southern U.S. . . . . . 31

30

return to couplet #28

  • Pilosity more abundant: in particular, erect hairs present on ventral surface of head, occiput, posterior margin of pronotum up to the tegulae, prosternum and antero-lateral margin of mesothoracic episterna. Dorsal margin of petiole high and angulate. Head larger than thorax, head width minus thorax width varying from 0.13 to 0.80 mm . . . . . Formica browni
  • Pilosity less abundant: in particular, erect hairs absents on mesothorax episterna, prosternum, occiput (sometimes 1-3), ventral surface of head (sometimes 1, very short), limited to median half of posterior margin on pronotum; dorsal margin of petiole low and weakly convex; head usually slightly narrower than thorax, head width minus thorax width varying from - 0.04 to + 0.13 mm . . . . . Formica retecta

31

return to couplet #28

  • Erect hairs on pronotum varying from 6 to 21 (mean = 15); length of longest hairs on the first tergite less than 0.50 X the length of clypeus; eyes larger, ocular index over 32.5 (fig. 442) . . . . . Formica gnava
  • Erect hairs on pronotum varying from 29 to 32; length of longest hairs on the first tergite more than 0.50 X the length of clypeus; eyes smaller, ocular index less than 32.5 (fig. 442) . . . . . Formica foreliana

32

return to couplet #28

  • Scapes shorter, scape length minus head length varying from - 0.10 to + 0.05 mm (mean = - 0.05 mm), scape index 97-105; petiolar tergite seen in profile slender and angulate at summit; ventral half of eyes projecting slightly beyond the margin of head seen in full face . . . . . Formica occulta
  • Scapes longer, scape length minus head length more than 0.05 mm, scape index over 103; petiolar tergite ·seen in profile thick and rounded at summit; ventral half of eyes largely projecting beyond the margin of head seen in full face. (Tentatively) . . . . . Formica xerophila