Key to Lasius males

This key to males 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: The males of the following species are unknown or were not available during the present study: Lasius alienoflavus, Lasius bicornis, Lasius crinitus, Lasius humilis, Lasius teranishii and Lasius vestitus.

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

1

 * Metapleural gland opening provided with guard hairs . . . . . 2


 * Metapleural gland opening lacking guard hairs . . . . . 12

2
return to couplet #1
 * Mandible lacking a preapical cleft, at the most the masticatory border feebly impressed in the middle; basal angle of mandible always broadly rounded, the masticatory border curving gradually into the basal border . . . . . 3


 * Mandible with a distinct preapical cleft (occasionally lacking in smaller individuals with HW less than about 1.00 mm.); basal angle often distinctly marked and clearly separating the masticatory and basal borders . . . . . 6

3
return to couplet #2
 * S1 exceeding 100 . . . . . Lasius productus


 * S1 less than 80 . . . . . 4

4
return to couplet #3
 * Standing hairs common on the scape . . . . . Lasius niger and . . . . . Lasius neoniger


 * Standing hairs rare or absent on the scape . . . . . 5

5
return to couplet #4
 * Subgenital plate arc-shaped, with a deeply concave posterior border sweeping back to the prominent posterolateral flanges, and with the anterior border correspondingly convex (Europe) . . . . . Lasius emarginatus


 * Subgenital plate subquadrate, the posterior border flat or weakly concave and the posterolateral flanges weakly developed or absent . . . . . Lasius alienus . . . . . Lasius crypticus and . . . . . Lasius sitiens

6
return to couplet #2
 * HW exceeding 1.00 mm.; basal angle of the mandible indistinct, the masticatory border merging gradually into the basal border (Eurasia) . . . . . Lasius brunneus


 * Either HW less than 1.00 mm., or else the basal angle of the mandible is distinct and clearly demarcates the masticatory and basal borders . . . . . 7

7
return to couplet #6
 * HW distinctly less than the width of the thorax just anterior to the regulae . . . . . 8


 * HW at least as great as the width of the thorax just anterior to the regulae (subg, Chthonolasius) . . . . . 9

8
return to couplet #7
 * ML exceeding 0.10 mm . . . . . Lasius pallitarsis


 * ML less than 0.08 mm subg. Cautolasius ( . . . . . Lasius flavus . . . . . Lasius nearcticus . . . . . Lasius talpa . . . . . Lasius fallax )

9
return to couplet #7
 * At least a broad longitudinal median strip of the second gastric tergite completely devoid of pubescence, its cuticular surface shining (eastern U.S.) . . . . . Lasius speculiventris


 * All of second gastric tergite covered with abundant pubescence which at least partly obscures the cuticular surface . . . . . 10

10
return to couplet #9
 * Petiole in side view thick, with a broadly rounded dorsal crest; standing hairs abundant around the entire cephalic: margin (seen in full face) posterior to the eyes (Eurasia) . . . . . Lasius carniolicus


 * Petiole in side view thin, with an acute dorsal crest; much of the cephalic margin posterior to the eyes bare of pilosity . . . . . 11

11
return to couplet #10
 * Longest hairs of the first gastric tergite exceeding 1.5 X the maximum width of the hind tibia at midlength; longest hairs of the posterior two-thirds of the clypeus exceeding 0.16 X the HW (eastern North America) . . . . . Lasius minutus


 * Longest hairs of the first gastrie: tergite not exceeding 1.1 X the maximum width of the hind tibia at midlength; longest hairs of the posterior two-thirds of the clypeus not exceeding 1).10 X the HW . . . . . 12

12
return to couplet #11
 * Maximum length of the hairs of the first gastric tergite 0.9-1.1 X the maximum width of the hind tibia at its midlength (Nova Scotia to Arizona) . . . . . Lasius subumbratus


 * Maximum length of the hairs of the first gastric tergite not exceeding 0.7 X the maximum width of the hind tibia at its midlength . . . . . Lasius umbratus and . . . . . Lasius rabaudi

13

 * Mandibles with seven well developed teeth including the apical; in frontal view the genae strongly convex, the head about as wide directly in front of the eyes as directly behind . . . . . Lasius buccatus


 * Masticatory border of mandible smooth, or at most with several small, irregular denticulae; in frontal view the genae feebly convex, the head directly in front of the eyes at the most G.9 X as wide as directly behind the eyes . . . . . 14

14
return to couplet #13
 * In side view the posterior margin of the petiolar scale is gently convex from the level of the posterior foramen to the dorsal crest, while the anterior border is parallel with it up to the petiolar spiracle and then turns abruptly posteriorly to produce a second face up to the crest (Japan and Korea) . . . . . Lasius spathepus


 * The petiolar scale in side view symmetrical, the posterior border showing the same degree of convexity as the anterior . . . . . 15

15
return to couplet #14
 * The petiole in side view with a narrow, sharp crest (Japan and Korea) . . . . . ''Lasius crispus


 * The petiole in profile with a thick, convex crest (England to Japan) . . . . . Lasius fuliginosus