Key to Lasius queens

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This key to queens is based on: Wilson, E. O. 1955. A monographic revision of the ant genus Lasius. Bulletin of the Museum of Comparative Zoology. 113:1-201.

Since this key is from 1955 it should be used with the caution. There are numberous species that are not included here, including the North American Acanthomyops. In 1955 Wilson noted: Excluding the rare Himalayan species return to Lasius alienoflavus (see key to workers).

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Lasius (this genus page provides links to other Lasius keys).

1

  • Metapleural gland opening provided with conspicuous guard hairs; in side view the scutum does not overhang the pronotum but shares with it the anterior thoracic convexity . . . . . 2
  • Metapleural gland opening lacking guard hairs; in side view the scutum overhangs the pronotum and claims all of the anterior thoracic convexity . . . . . 22

2

return to couplet #1

  • HW distinctly less than the width of the thorax just anterior to the regulae . . . . . 3
  • HW about the same as or greater than the width of the thorax just anterior to the regulae . . . . . 13

3

return to couplet #2

  • Length of terminal segment of maxillary palp exeeeding 0.1 X the HW, even if only slightly . . . . . 4
  • Length of terminal segment of maxillary palp less, than 0.1 X the HW, even if by only a slight amount . . . . . 10

4

return to couplet #3

  • When viewed with mandibles opened and the head held in perfect full face (at maximum head length and with the occipital and anterior clypeal borders horizontally aligned), the median third of the anterior border of the median clypeal lobe is flat or emarginate; all the queens of a nest series with at least one and often two or three offset teeth present on the basal angle and along the basal border of the mandible (North America) . . . . . Lasius pallitarsis
  • When viewed as above, the median third of the anterior border of the median clypeal lobe convex or angulate, never flat or emarginate; the posterior basal tooth, with rare exceptions, always aligned with the adjacent teeth of the masticatory border; when it is offset, this condition occurs in a minority of the individuals of the nest series and usually only on one mandible in any individual, and secondary offset teeth are never present on the basal border . . . . . 5

5

return to couplet #4

  • When viewed with the mandibles opened and the head held in perfect full face, the anterior border of the median clypeal lobe is angulate, with two straight or very feebly convex sides meeting in a blunt point at the midline; in a large part of any nest series the penultimate basal tooth is distinctly reduced in size relative to the two flanking teeth (North American species only) . . . . . 6
  • When viewed as above, the anterior border of the median clypeal lobe is broadly and evenly rounded; with rare exceptions the penultimate basal tooth is about the same size as the two flanking teeth . . . . . 7

6

return to couplet #5

7

return to couplet #5

  • Length of terminal segment of maxillary palp 0.32-0.34 mm. in the several series measured (Japan) . . . . . Lasius productus
  • Length of terminal segment of maxillary palp not exceeding 0.26 mm . . . . . 8

8

return to couplet #7

  • Scape with few or no standing hairs, although decumbent hairs may be numerous . . . . . 9

9

return to couplet #8

  • Scape with numerous decumbent hairs outstanding above the pubescence . . . . . Lasius emarginatus

10

return to couplet #3

  • Scape with numerous standing hairs (eastern Asia) . . . . . Lasius talpa

11

return to couplet #10

  • Tibiae with numerous standing hairs (western U.S.) . . . . . Lasius fallax

12

return to couplet #11

  • Terminal segment of maxillary palp usually longer than the penultimate (see diagnosis) (eastern North America to Wyoming) . . . . . Lasius nearcticus
  • Terminal segment not exceeding in length the penultimate segment (Holarctic) . . . . . Lasius flavus

13

return to couplet #2

  • HW 0.76-0.78 mm.; petiole in side view thick, resembling an inverted U (Eurasia) . . . . . Lasius carniolicus
  • HW exceeding 1.00 mm.; petiole in side view thinner, with a narrow dorsal crest . . . . . 14

14

return to couplet #13

  • Alitrunk and gaster covered with extremely long, fine, predominantly appressed hairs; HW of single specimen measured 1.99 mm. (Himalayas) . . . . . Lasius crinitus
  • Pilosity of alitrunk and gaster otherwise; HW never exceeding 1.75 mm . . . . . 15

15

return to couplet #14

  • The dorsal border of the petiole in frontal view narrow and deeply emarginate, the depth of the emargination measured from the level of the bicornuate dorsal crest to the bottom of the emargination at least as great as the width of the emargination measured at the level of the middle of the depth measurement (Eurasia) . . . . . Lasius bicornis
  • Dorsal border of the petiole with never more than a right-angular emargination . . . . . 16

16

return to couplet #15

17

return to couplet #16

  • First gastric tergite densely covered with coarse standing hairs, the longest of which exceed in length the maximum width of the hind tibia at its midlength (eastern North America) . . . . . Lasius minutus
  • First gastric tergite with relatively sparse, fine hairs, the longest of which do not exceed in length 0.8 X the maximum width of the hind tibia at its midlength (southwestern U. S.) . . . . . Lasius humilis

18

return to couplet #16

  • The longest hairs of the first gastric tergite exclusive of the extreme posterior strip not exceeding in length 0.5 X the. maximum width of the hind tibia at its midlength . . . . . 19
  • The longest hairs of the first gastric tergite, exclusive of the extreme posterior strip, about as long as the maximum width of the hind tibia at its midlength . . . . . 21

19

return to couplet #18

  • Dorsal surfaces of second and third gastric tergites completely devoid of pubescence and strongly shining (eastern U.S.) . . . . . Lasius speculiventris
  • Dorsal surfaces of second and third gastric tergites covered by appressed pubescence which often partly obscures the shining cuticular surface . . . . . 20

20

return to couplet #19

  • Scapes conspicuously flattened, the minimum width at midlength not exceeding 0.10 mm. (Fig. lo5) (Eurasia) . . . . . Lasius rabaudi
  • Scapes short-elliptical in cross-section, the minimum width at midlength not less than 0.11 mm, (Holarctic) . . . . . Lasius umbratus

21

return to couplet #18

  • Pilosity of anterior gastric tergites predominantly erect . . . . . Lasius vestitus
  • Pilosity of anterior gastric tergites predominantly decumbent-subdecumbent . . . . . Lasius subumbratus

22

return to couplet #1

  • A “beta” form, with conspicuously flattened scapes, femora, tibiae, and metatarsi; thorax completely lacking hairs of any kind . . . . . 23
  • An “alpha” form, showing no conspicuous flattening of the appendages; thorax with abundant hairs . . . . . 24

23

return to couplet #22

  • Head about as broad as long; petiolar scale symmetrical in side view, with both the anterior and posterior faces gently convex . . . . . Lasius orientalis
  • Head much broader than long, anterior border of petiolar scale in side view angulate, being parallel with the posterior border up to the level of the petiolar spiracle but then bending abruptly back to form an oblique face up to the dorsal crest . . . . . Lasius spathepus

24

return to couplet #22

  • Many of the body and appendage hairs curved at the tip or sinuate, those on the appendages often curving back to touch the cuticular surface again; body pubescence sparse or absent, the cuticular surface smooth and shining . . . . . Lasius crispus
  • Few or no hairs curved at the tip or sinuate; body covered with appressed pubescence which at least partly obscures the cuticular surface . . . . . 25

25

return to couplet #24

  • A sharp median carina runs from the frontal triangle to a small shallow pit in the center of the clypeus; C1 about 97 . . . . . Lasius buccatus
  • Median clypeal carina weakly developed and running most of the length of the clypeus, not ending in a central pit; C1 as least 100 . . . . . Lasius fuliginosus