Key to New England Lasius

This key is modified from the 2012 book A Field Guide to the Ants of New England
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1

The maxillary palps are short and inconspicuous, and with three segments; these ants give off a very strong lemony/citronella odor when disturbed; the angle between the dorsal (top) and rear (declivity) faces of the propodeum is rounded (claviger group) . . . . . 2

Maxillary palps long and conspicuous, and with six segments; ants do not give off a lemony/citronella odor when disturbed; the angle between the dorsal face of the propodeum and its declivity is sharp . . . . . 7

2

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The hairs on the gaster have feathery (plumose) tips (best viewed obliquely using a dissecting microscope at 50-100× magnification); currently unknown from New England Lasius plumopilosus

Hairs on gaster have straight tips without feathered ends . . . . . 3

3

return to couplet #2

The petiole, viewed in profile, is sharp and pointed; when viewed from the front, the petiole has a shallow-to-sharp depression in its center; cheeks, viewed from the side, with erect hairs sparse, or if dense, limited to the upper (posterior) 2/3 of the cheeks . . . . . 4

Petiole, viewed in profile, is rounded and blunt; cheeks, viewed from the side, with erect hairs distributed over the entire surface . . . . . 6

4

return to couplet #3

The hairs on the body are thin and wispy; the hairs on the cheeks are short . . . . . Lasius subglaber

Hairs on the body are thick and coarse; the hairs on the cheeks are long . . . . . 5

5

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Erect hairs are present on all surfaces of all segments of the gaster; hairs on the ventral surface of the head are long . . . . . Lasius claviger

Erect hairs are present on the entire surface of the first segment of the gaster but are present only on the posterior edges of the second and third segments; few hairs on the ventral surface of the head . . . . . Lasius interjectus

6

return to couplet #3

The ant is very hairy all over; there are many long hairs on the cheeks . . . . . Lasius latipes

Hairs on the propodeum denser than elsewhere; hairs on the cheeks are short . . . . . Lasius murphyi

7

return to couplet #1

The ant has large eyes (eye length > 1/5th the width of the head); the color of the ant is golden-brown to dark-brown (niger group) . . . . . 8

Eyes smaller (eye length < 1/6th the width of the head); nests can be deep underground; the color is yellow-to-brown . . . . . 11

8

return to couplet #7

The basal tooth of the mandible (i.e., the tooth closest to head) is offset from, and smaller than, the others; there are 7 teeth on the mandible, but because the basal tooth is offset, it may appear that there are only 6; the anterior margin of the clypeus is broadly curved; erect hairs are present on the scape and tibia; color dark brown . . . . . Lasius pallitarsis

Basal tooth of the mandible aligned with the rest of the teeth and normal in size; there are 7 teeth on the mandible and all are usually visible; the anterior margin of the clypeus may be broadly curved or sharply angular in the middle . . . . . 9

9

return to couplet #8

There are usually no erect hairs (if present, always < 10) on the antennal scape or tibia; color dark brown; forested habitats in New England . . . . . Lasius americanus (the North American species long considered to be Lasius alienus has been shown to be a separate species. L alienus is restricted to the Palearctic and L. americanus is the name for the North America species).

There are many erect hairs on the antennal scape (usually) and on the tibia (always); color golden-brown; found in open habitats . . . . . 10

10

With the mandibles fully open and the head positioned in full-face view, the anterior margin of the clypeus is sharply angled; the basal 2 – 3 teeth on the mandible are irregularly spaced and the second tooth is usually much smaller than the 1st or 3rd tooth . . . . . Lasius neoniger

10b. With the mandibles fully open and the head positioned in full-face view, the anterior margin of the clypeus is broadly curved; the basal 2 – 3 teeth on the mandible are regularly spaced and equal in size . . . . . L. cf. niger

11

return to couplet #7

Eyes much shorter than 1/6th the width of the head and with < 35 facets (flavus group) . . . . . 12

Eyes about 1/6th as long as the head is wide and always with > 35 facets; all species are temporary social parasites on other species of Lasius (umbratus group) . . . . . 13

12

return to couplet# 11

The terminal segment of the maxillary palp is usually shorter than, but never longer than, the next-to-last segment; color yellow to dark yellow-brown; usually in open habitats . . . . . Lasius brevicornis

Terminal segment of the maxillary palp always longer than next-to-last segment; color pale-to-medium yellow; usually in forested habitats . . . . . Lasius nearcticus

13

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The second gastral segment is shiny and lacks appressed pubescence, but may have at most a few scattered erect hairs; color dark-yellow to medium-brown; occurs in bogs, fens, and moist woods . . . . . Lasius speculiventris

Second gastral segment dull, with both appressed pubescence and many erect hairs . . . . . 14

14

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The longest hairs of the first gastral segment are short and stubble-like: < ½ the width of the hind tibia at its midpoint . . . . . 15

Longest hairs of the first gastral segment are long (> 2/3 the width of the hind tibia); found in moist, disturbed, and early successional habitats . . . . . 16

15

return to couplet #14

The petiole viewed from front (or rear) is concave on top; no erect hairs are present on the scape or tibia Lasius aphidicola

Petiole viewed from front (or rear) is convex on top; erect hairs present on the scape and hind tibia. Lasius cf. umbratus - an undescribed species

16

return to couplet #14

The hairs on the gaster are between 2/3rd and 4/5th the maximum width of the hind tibia; there are some erect hairs present on the tibia; petiole viewed from front or rear evenly convex at top; color is clear yellow . . . . . Lasius subumbratus

Hairs on the gaster as long or longer than the maximum width of the hind tibia; no erect hairs present on the tibia; color is brownish-yellow; open habitats, especially bogs, fens, and sedge meadows . . . . . Lasius minutus