Key to New England Lasius

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

 * 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
return to couplet #1
 * 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
return to couplet #4


 * 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 flavus


 * 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
return to couplet #11
 * 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
return to couplet #13
 * 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 umbratus
 * 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