Key to Lachnomyrmex species

This worker key is based on: Feitosa, R.M. & Brandão, C.R.F. 2008. A taxonomic revision of the Neotropical myrmicine ant genus Lachnomyrmex Wheeler (Hymenoptera: Formicidae). Zootaxa 1890, 1-49.

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Lachnomyrmex

1

 * First tergite of gaster with long (similar in length to antennal scape), flexuous hairs at least on anterior third, near the insertion of postpetiole; usually over entire surface (Fig. a) . . . . . 2


 * First tergite of gaster entirely devoid of long hairs (Fig. b) . . . . . 9

2
return to couplet #1
 * Metanotal groove obsolete, so that the dorsal outline of promesonotum continues to the propodeum in a slight declivity (Fig. a) . . . . . 3


 * Metanotal groove impressed, so that the dorsal outline of promesonotum continues to the propodeum in an abrupt declivity (Fig. b) . . . . . 4

3
return to couplet #2
 * Teeth of propodeal lobes wide dorsoventrally, in lateral view; petiolar node subtriangular; dorsum of post-petiole considerably convex and rugose; first tergite of gaster completely covered by long, flexuous hairs (continental Central America) . . . . . Lachnomyrmex scrobiculatus
 * Teeth of propodeal lobes narrow dorsoventrally, in lateral view; petiolar node dorsally flat; dorsum of postpetiole weakly convex and predominantly smooth; first tergite of gaster with about five long, sparse, flexuous hairs (Guyana) . . . . . Lachnomyrmex platynodus

4
return to couplet #2
 * Larger species; mesosoma length (WL) ≥ 1.20mm (Costa Rica and Colombia) . . . . . Lachnomyrmex grandis
 * Smaller species; mesosoma length (WL) < 1.20mm . . . . . 5

5
return to couplet #4
 * Propodeal spines very well developed, at least twice longer than the distance between their basis; petiole extremely elongate, at least three times longer than broad in dorsal view (Colombia) . . . . . Lachnomyrmex longinodus
 * Propodeal spines less than twice longer than the distance between their basis; petiole shorter, less than three times long than broad in dorsal view . . . . . 6

6
return to couplet #5
 * Mesosoma covered by thick and somewhat continuous rugae, transverse on anterior portion of pronotum, grading to longitudinal on rest of promesonotum and propodeum; in lateral view, promesonotum moderately convex, only slightly above the level of propodeum (Fig. a) . . . . . 7


 * Mesosoma covered by finer and shorter rugae; in lateral view, promesonotum strongly convex, well above the level of propodeum (Fig. b) . . . . . 8

7
return to couplet #6
 * Petiolar node relatively low, weakly raised dorsally; first tergite of gaster rather opaque and completely covered by long, flexuous hairs (Colombia) . . . . . Lachnomyrmex fernandezi
 * Petiolar node relatively high, subtriangular; first tergite of gaster strongly shining and with long, flexuous hairs only on the anterior third, near the insertion of postpetiole (Panama) . . . . . Lachnomyrmex mackayi

8
return to couplet #6
 * Vertexal margin of head virtually flat and relatively broad (LC ≥ 0.73mm); mesosoma length (WL) ≥ 0.90mm; metanotal groove relatively shallow and broadly impressed, without a distinct posterior limit, so that dorsal face of propodeum forms a separate plane relative to convex promesonotum (Costa Rica) . . . . . Lachnomyrmex laticeps
 * Vertexal margin of head convex and shorter (LC < 0.73mm); mesosoma length (WL) < 0.90mm; metanotal groove narrow and deeply impressed (Trinidad and central-northern South America) . . . . . Lachnomyrmex pilosus

9
return to couplet #1
 * Head and mesosoma covered by continuous rugae, transverse on anterior portion of pronotum, grading to longitudinal on rest of promesonotum and propodeum (Fig. a); dorsum of postpetiole mostly smooth and with a raised boss medially; subpostpetiolar process usually well developed . . . . . 10


 * Head and mesosoma covered by irregular short rugae (Fig. b); dorsum of postpetiole mostly sculptured and without a raised boss medially; subpostpetiolar process absent or weakly developed . . . . . 11

10
return to couplet #9
 * Cephalic dorsum with dense, subparallel rugae; compound eyes relatively large (EL > 0.15mm), with about 10 facets at maximum diameter; mesosoma length (WL) ≥ 0.85mm; dorsum of postpetiole entirely smooth and shining; gaster much darker than the rest of body (Costa Rica) . . . . . Lachnomyrmex regularis
 * Cephalic dorsum with rather sparser, vermiculate rugae; compound eyes smaller (EL ≤ 0.15mm), with about 7 facets at maximum diameter; mesosoma length (WL) < 0.85mm; dorsum of postpetiole with short and weak rugulation; gaster slightly darker than the rest of body (Costa Rica and Panama) . . . . . Lachnomyrmex haskinsi

11
return to couplet #9
 * Metanotal groove deeply impressed, so that the dorsal outline of promesonotum reaches the propodeum in an abrupt angle in profile; propodeal spines relatively thin (Venezuela) . . . . . Lachnomyrmex lattkei
 * Metanotal groove shallowly impressed or obsolete, so that the dorsal outline of promesonotum reaches the propodeum in a slight declivity in profile; propodeal spines with wider bases . . . . . 12

12
return to couplet #11
 * Mesosoma sparsely rugose; in lateral view, promesonotum relatively low, only slightly above the level of propodeum; apex of propodeal spines curved downwards (northern Argentina and southeastern Brazil) . . . . . Lachnomyrmex plaumanni
 * Mesosoma more densely rugose; in lateral view, promesonotum higher, well above the level of propodeum; apex of propodeal spines straight to curved upwards . . . . . 13

13
return to couplet #12
 * Teeth of propodeal lobes well developed and strongly projected over petiolar peduncle; dorsum of post-petiole strongly convex and densely rugose (Costa Rica and Panama) . . . . . Lachnomyrmex longinoi
 * Teeth of propodeal lobes reduced, not strongly projected over petiolar peduncle; dorsum of postpetiole weakly convex and more sparsely rugose . . . . . 14

14
return to couplet #13
 * Dorsum of postpetiole with less than 10 long flexuous hairs, usually six (northeastern Brazil) . . . . . Lachnomyrmex nordestinus
 * Dorsum of postpetiole with 10 or more long flexuous hairs . . . . . 15

15
return to couplet #14
 * Promesonotum strongly compact and elevated; apex of propodeal spines slightly directed upwards; dorsum of postpetiole with much more than 10 long, flexuous hairs (Amazonian Brazil) . . . . . Lachnomyrmex amazonicus
 * Promesonotum somewhat more elongate; propodeal spines straight; dorsum of postpetiole with about 10 long, flexuous hairs (southeastern Brazil to state of Bahia) . . . . . Lachnomyrmex victori