Key to Adelomyrmex of the New World mainland

This worker key is based on: Longino, J.T. 2012. A review of the ant genus Adelomyrmex Emery 1897 (Hymenoptera, Formicidae) in Central America. Zootaxa 3456, 1–35.

This key contains only species known from the mainland Americas. Species from Melanesia and elsewhere, including a species from Isla del Coco, are not included.

1

 * Postpetiole in profile with a posterior triangular projection extending over gaster and closely appressed to it; in dorsal view postpetiole longer than wide; face and mesosomal sculpture of vermiculate rugae, never with beaded appearance; HW 0.5–0.6. Mexico to Costa Rica . . . . . Adelomyrmex silvestrii


 * Postpetiole in profile may have a posterior rim or slight projection over gaster, but rarely with a large triangular projection, in dorsal view about as wide as long or wider than long, if longer than wide, face and mesosomal rugae beaded or HW > 0.8 margin . . . . . 2

2
return to couplet #1
 * Scape with 1–4 long erect setae projecting above underlying dense pubescence margin . . . . .3


 * Scape lacking long erect setae margin . . . . . 6

3
return to couplet #2
 * Mandible lacking differentiated basal and masticatory margins; counting from basal tooth on basal margin (near mandibular insertion), second tooth closer to basal tooth than to third tooth, or equidistant betweeen them margin . . . . . 4


 * Mandible with differentiated masticatory and basal margin; with a single tooth at base of basal margin that is well separated from teeth of the masticatory margin (masticatory margin dentition variable, may have 5 or 6 teeth, apical 3 always present and large, basal 2–3 often reduced to small denticles or absent) margin . . . . . 5

4
return to couplet #3
 * Metanotal groove not impressed in profile view; setae on dorsal surfaces of head, mesosoma, and gaster long and erect; petiolar node more quadrate in profile, posterior and dorsal faces more distinctly separated by a transverse carina; rugae of lateral and dorsal faces of pronotum wavy but somewhat longitudinally oriented. Southern Mexico to Honduras . . . . . Adelomyrmex dentivagans


 * Metanotal groove impressed; setae on dorsal surfaces shorter, denser, and more decumbent; petiolar node more rounded dorsally; pronotal rugae more reticulate, with no longitudinal orientation. Northern Mexico . . . . . . Adelomyrmex nortenyo

5
return to couplet #3
 * Anterior and dorsal face of pronotum less sharply differentiated in profile; posterior margin of postpetiole lacking pronounced transverse rim. Honduras to Costa Rica . . . . . . Adelomyrmex longinoi


 * Anterior and dorsal face of pronotum more sharply differentiated in profile; posterior margin of postpetiole with sharp projecting transverse rim. Southern Mexico to Honduras . . . . . Adelomyrmex marginodus

6
return to couplet #2
 * Mandible lacking differentiated basal and masticatory margins; counting from basal tooth on basal margin (near mandibular insertion), second tooth closer to basal tooth than to third tooth, or equidistant betweeen them margin . . . . . 7


 * Mandible with differentiated masticatory and basal margin; with a single tooth at base of basal margin that is well separated from teeth of the masticatory margin margin . . . . . 9

7
return to couplet #6
 * Size small, HW < 0.55. Colombia, Ecuador . . . . . Adelomyrmex cristiani


 * Larger, HW > 0.55. Central America margin . . . . . 8

8
return to couplet #7
 * Strongly bicolored, with dark brown head and mesosoma, light yellow brown gaster; metanotal groove impressed. Southern Mexico, Guatemala . . . . . Adelomyrmex mackayi


 * Concolorous dark brown; metanotal groove not impressed. Guatemala . . . . . Adelomyrmex quetzal

9
return to couplet #6
 * Face smooth and shining, or smooth and shining with coarse foveae; if rugose sculpture present it is faint and restricted to anterior and lateral margins margin . . . . . 10


 * Face densely rugose or costate throughout margin . . . . . 14

10
return to couplet #9
 * Face completely smooth and shining, lacking foveae margin


 * Face with sparse large foveae, interspaces smooth and shining margin . . . . . 12

11
return to couplet #10
 * Dorsal promesonotum completely smooth and shining. Southern Mexico to Honduras . . . . . Adelomyrmex micans


 * Dorsal promesonotum longitudinally rugose. Honduras . . . . . Adelomyrmex anxiocalor

12
return to couplet #10
 * HW approximately 0.7mm; propodeum depressed below level of promesonotum, juncture of promesonotum and propodeum steplike. Costa Rica . . . . . Adelomyrmex brenesi


 * HW < 0.6mm; promesonotum and dorsal face of propodeum form a continuous convexity margin . . . . . 13

13
return to couplet #12
 * Eyes with 7–8 ommatidia; HW approximately 0.5 mm. Costa Rica . . . . . Adelomyrmex foveolatus


 * Eyes with 1 ommatidium; HW < 0.5 mm. Costa Rica . . . . . Adelomyrmex minimus

14
return to couplet #9
 * Dorsal promesonotum completely smooth and shining margin . . . . . 15


 * Dorsal promesonotum rugose or costate margin . . . . . 16

15
return to couplet #15
 * Color dark brown to black; confluent dorsal and posterior faces of propodeum with four or more transverse rugae above epipetiolar carina, subequal in size; gastral pilosity short, much shorter than height of postpetiole above posterior carina. Costa Rica . . . . . Adelomyrmex laevigatus


 * Color red brown; confluent dorsal and posterior faces of propodeum with a single strong transverse ruga between propodeal spines, no rugae or a very faint ruga between it and epipetiolar carina, 1–2 faint rugae above it; gastral pilosity usually longer and denser, about as long as height of postpetiole above posterior carina. Costa Rica, Honduras . . . . . Adelomyrmex microps

16
return to couplet #15
 * Dorsal promesonotum vermiculate rugose, without strong longitudinal orientation of rugae (see additional discussion under A. myops for problematic differentiation of A. myops and A. paratristani in some cases) margin . . . . . 17


 * Dorsal promesonotum more linearly rugose, with substantial longitudinal orientation of rugae margin . . . . . 18

17
return to couplet #16
 * Promesonotum strongly produced, highest at mesonotum, steeply dropping to dorsal face of propodeum; posterior faces of petiole and postpetiole each with dorsal transverse ruga, such that in profile nodes appear somewhat flat-topped and with posterior tooth. Southern Mexico, Guatemala . . . . . Adelomyrmex metzabok


 * Promesonotum lower, not strongly elevated above dorsal face of propodeum; petiolar and postpetiolar nodes more rounded dorsally in profile. Guatemala to Panama, Galapagos . . . . . Adelomyrmex myops

18
return to couplet #16
 * Rugae of face and mesomal dorsum with beaded appearance; HW < 0.6; postpetiole distinctively shaped with short, concave, smooth and shining posterior face that is closely appressed to gastral dorsum, sharply separated from sculptured dorsal face by a pronounced sharp transverse carina; with dorsal pilosity abundant or nearly lacking. Southern Mexico . . . . . Adelomyrmex betoi


 * Rugae of face and mesosomal dorsum not beaded; HW variable; postpetiole with taller posterior face that is not closely appressed to gastral dorsum and not sharply divided from dorsal face margin . . . . . 19

19
return to couplet #18
 * Antennal fossa with large completely smooth and shining patch that extends to level of posterior margin of compound eye, sharply differentiated from coarse sculpture that covers the rest of the face; petiolar and postpetiolar nodes largely smooth and shining, evenly rounded, without differentiated anterior, dorsal, and posterior faces; hind and mid tibia lacking long erect setae that project above subdecumbent pilosity. Costa Rica . . . . . Adelomyrmex bispeculum


 * Antennal fossa completely sculptured, or with a small smooth area that does not extend to posterior margin of eye; petiolar and postpetiolar nodes with variable extent of coarse rugae and often with more differentiated anterior, dorsal, and posterior faces; tibial setae present or absent margin . . . . . 20

20

 * HW > 0.7 margin . . . . . 21


 * HW < 0.7 margin . . . . . 23

21
return to couplet #20
 * Mandible with six teeth on masticatory margin margin . . . . . 22


 * Mandible with five teeth on masticatory margin. Southern Mexico, Guatemala . . . . . Adelomyrmex robustus

22
return to couplet #21
 * Uniformly dark brown; face and mesosoma more regularly and evenly striate; postpetiole in dorsal view wider than long, in lateral view with posterodorsal carina less developed. Colombia . . . . . Adelomyrmex grandis


 * Somewhat bicolored, with dark head and mesosoma, lighter red brown gaster; face and mesosoma more irregularly reticulate-striate; postpetiole in dorsal view longer than wide, in lateral view with more pronounced posterodorsal carina or projection. Colombia . . . . . Adelomyrmex vaderi

23
return to couplet #20
 * Face and mesosomal sculpture very regularly costate, with broad, flattened costae and narrow interspaces margin . . . . . 24


 * Face and mesosomal sculpture more irregularly rugose, rugae sharper and with broader interspaces margin . . . . . 25

24
return to couplet #23
 * Promesonotum strongly convex anteriorly, with an asymmetrical profile. Amazonian Brazil, Ecuador, Peru . . . . . Adelomyrmex striatus


 * Promesonotum more evenly convex, more symmetrical, and not produced anteriorly. Colombia . . . . . Adelomyrmex costatus

25
return to couplet #23
 * Dorsal pilosity of head, mesosoma, and gaster relatively short, dense, and subdecumbent; FSH usually < 0.06 mm, FSI < 0.1; HW 0.48–0.62 (queen mesonotum largely smooth and shining in northern part of range, from Honduras northward; grading to form in Nicaragua and Costa Rica with sculpture like A. paratristani) (problematic specimens of A. myops may key here; see additional discussion under A. myops) (some specimens of A. cristiani, from South America, may key here; see additional discussion under A. cristiani). Southern Mexico to Costa Rica . . . . . Adelomyrmex tristani


 * Dorsal pilosity of head, mesosoma, and gaster relatively long, less dense, and more erect; FSH usually > 0.06 mm, FSI > 0.1; HW 0.54–0.71 (queen mesonotum longitudinally rugose except for anteromedian triangular patch that is smooth and shiny). Southern Mexico to Nicaragua . . . . . Adelomyrmex paratristani