Lachnomyrmex

Feitosa, Rodrigo M. & Brandão, Carlos Roberto F., 2008, A taxonomic revision of the Neotropical myrmicine ant genus Lachnomyrmex Wheeler (Hymenoptera: Formicidae), Zootaxa 1890, pp. 1-49 : 8-11

Key to the identification of Lachnomyrmex workers

(The SEM illustrations will help decide which entry should be followed and refers to the key couplet immediately above. After the taxonomic account, all species are illustrated using high definition pictures.)

1a. 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.............................................................2

1b. First tergite of gaster entirely devoid of long hairs.....................................................................................9

2a. Metanotal groove obsolete, so that the dorsal outline of promesonotum continues to the propodeum in a slight declivity.............................................................................................................................................3

2b. Metanotal groove impressed, so that the dorsal outline of promesonotum continues to the propodeum in an abrupt declivity.......................................................................................................................................4

3a. Teeth of propodeal lobes wide dorsoventrally, in lateral view; petiolar node subtriangular; dorsum of postpetiole considerably convex and rugose; first tergite of gaster completely covered by long, flexuous hairs (continental Central America) ( Fig. 16 ) ..................................................... L. scrobiculatus Wheeler, 1910

3b. 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) ( Fig. 13 )................................................................................. L. platynodus sp. n.

4a. Larger species; mesosoma length (WL) ≥ 1.20mm ( Costa Rica and Colombia) ( Fig. 4 ) ............................. .......................................................................................................... L. grandis Fernández & Baena, 1997

4b. Smaller species; mesosoma length (WL) <1.20mm ...................................................................................5

5a. 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) ( Fig. 8 ).................... ..................................................................................................... L. longinodus Fernández & Baena, 1997

5b. 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

6a. 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..........................................................................7

6b. Mesosoma covered by finer and shorter rugae; in lateral view, promesonotum strongly convex, well above the level of propodeum...............................................................................................................................8

7a. Petiolar node relatively low, weakly raised dorsally; first tergite of gaster rather opaque and completely covered by long, flexuous hairs ( Colombia) ( Fig. 3 ).................................................... L. fernandezi sp. n.

7b. 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) ( Fig.10 )....... L. mackayi sp. n.

8a. 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) ( Fig. 6 )........................................................................................................................................ L. laticeps sp. n.

8b. 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) (Fig. 12) ............ ................................................................................................................................. L. pilosus Weber, 1950

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

9b. Head and mesosoma covered by irregular short rugae; dorsum of postpetiole mostly sculptured and without a raised boss medially; subpostpetiolar process absent or weakly developed....................................11

10a. 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) ( Fig. 15 ) ... L. regularis sp. n.

10b. 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) ( Fig. 5 ) .......... ................................................................................................................................ L. haskinsi Smith, 1944

11a. 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) ( Fig. 7 ) ........... L. lattkei sp. n.

11b. 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

12a. 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) ( Fig. 14 ) ...................................................................................................... L. plaumanni Borgmeier, 1957

12b. Mesosoma more densely rugose; in lateral view, promesonotum higher, well above the level of propodeum; apex of propodeal spines straight to curved upwards.....................................................................13

13a. Teeth of propodeal lobes well developed and strongly projected over petiolar peduncle; dorsum of postpetiole strongly convex and densely rugose ( Costa Rica and Panama) ( Fig. 9 ) .............. L. longinoi sp. n.

13b. Teeth of propodeal lobes reduced, not strongly projected over petiolar peduncle; dorsum of postpetiole weakly convex and more sparsely rugose.................................................................................................14

14a. Dorsum of postpetiole with less than 10 long flexuous hairs, usually six (northeastern Brazil) ( Fig. 11 ) .. ..................................................................................................................................... L. nordestinus sp. n.

14b. Dorsum of postpetiole with 10 or more long flexuous hairs...................................................................15

15a. 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) ( Fig. 2 ) ................... .................................................................................................................................... L. amazonicus sp. n.

15b. Promesonotum somewhat more elongate; propodeal spines straight; dorsum of postpetiole with about 10 long, flexuous hairs (southeastern Brazil to state of Bahia) ( Fig. 17 ) ................................. L. victori sp. n.

Figures

FIGURE 2. Paratype worker of Lachnomyrmex amazonicus from Pará, Brazil: A, head in full face view; B, lateral view; C, dorsal view. Image by Michele Esposito, specimen CASENT 0173882.

FIGURE 3. Holotype worker of Lachnomyrmex fernandezi from Santander, Colombia: A, head in full face view; B, lateral view; C, dorsal view. Image by Michele Esposito, specimen CASENT 0173880.

FIGURE 4. Worker of Lachnomyrmex grandis from Heredia, Costa Rica: A, head in full face view; B, lateral view; C, dorsal view. Image by John Longino, specimen INBIOCRI 002720565.

FIGURE 5. Worker of Lachnomyrmex haskinsi from Heredia, Costa Rica: A, head in full face view; B, lateral view. Image by John Longino, specimen INBIOCRI 001237374.

FIGURE 6. Holotype worker of Lachnomyrmex laticeps from Heredia, Costa Rica: A, head in full face view; B, lateral view. Image by John Longino, specimen INBIOCRI 0003622583.

FIGURE 7. Holotype worker of Lachnomyrmex lattkei from Falcón, Venezuela: A, head in full face view; B, lateral view; C, dorsal view. Image by Michele Esposito, specimen CASENT 0173879.

FIGURE 8. Holotype worker of Lachnomyrmex longinodus from Nariño, Colombia: A, head in full face view; B, lateral view; C, dorsal view. Image by Michele Esposito, specimen CASENT 0173875.

FIGURE 9. Worker of Lachnomyrmex longinoi from Puntarenas, Costa Rica: A, head in full face view; B, lateral view; C, dorsal view. Image by April Nobile, specimen PSW 7771 - 6.

FIGURE 10. Holotype worker of Lachnomyrmex mackayi from Chiriqui, Panama: A, head in full face view; B, lateral view; C, dorsal view. Image by Michele Esposito, specimen CASENT 0173883.

FIGURE 11. Paratype worker of Lachnomyrmex nordestinus from Pernambuco, Brazil: A, head in full face view; B, lateral view; C, dorsal view. Image by Michele Esposito, specimen CASENT 0173878.

FIGURE 13. Holotype worker of Lachnomyrmex platynodus from Mt. Ayanganna, Guyana: A, head in full face view; B, lateral view; C, dorsal view. Image by Michele Esposito, specimen CASENT 0173881.

FIGURE 14. Worker of Lachnomyrmex plaumanni from São Paulo, Brazil: A, head in full face view; B, lateral view; C, dorsal view. Image by Michele Esposito, specimen CASENT 0173876.

FIGURE 15. Holotype worker of Lachnomyrmex regularis from Guanacaste, Costa Rica: A, head in full face view; B, lateral view; C, dorsal view. Image by Michele Esposito, specimen INBIOCRI 001613693.

FIGURE 16. Worker of Lachnomyrmex scrobiculatus from Heredia, Costa Rica: A, head in full face view; B, lateral view; C, dorsal view. Image by April Nobile, specimen CASENT 0103243.

FIGURE 17. Paratype worker of Lachnomyrmex victori from Santa Catarina, Brazil: A, head in full face view; B, lateral view; C, dorsal view. Image by Michele Esposito, specimen CASENT 0173877.