Genera Insectorum: Emery's key to Camponotus subgenera of the New World

KEY TO THE SUBGENERA OF CAMPONOTUS FOR THE NEW WORLD

Below is Emery's (1925) key to the subgenera of Camponotus for the New World. Note the following: (1) hundreds of new species have been described since Genera Insectorum; (2) in some cases, there have been changes to the rank and limits of the subgenera, particularly splitting; and (3) the parenthetical numbers after the taxon names correspond to Emery's original ordination of the subgenera and their current ranks. What follows first is the leading text (translated) from Emery's original key. What follows is edited and translated text leading the key from Emery (1925):

"Given the large number of groups to be distinguished and the relative inconstancy of the characters on which they are established, I resolved to make two separate keys, one for the subgenera inhabiting the Old World and Australia, and the other for the American subgenera. The small groups, common to both hemispheres, are included in both keys.

In the Old World key, leads (= lugs) 10 and 16 may challenge the identifier, especially if only minor workers are available. Additionally, the subgenera which have numerous and highly variable species are interconnected by gradual transitions, such as Tanaemyrmex, Myrmophyma, Myrmamblys, and other small groups.

In the New World key, leads 7 and 13 are difficult, and the subgenera Tanaemyrmex, Camponotus, Myrmaphaenus, and Pseudocolobopsis on the one hand, and Myrmaphaenus and Myrmobrachys on the other, and have transitions from one group to another the other.

I confess that my keys are far from satisfying to me, and that I am afraid that beginning myrmecologists will be daunted by the considerable number of subgenera and by the various weaknesses of their diagnostic characters. The latter issue might have gained precision by increasing the number of subgeneric divisions, as previously mentioned. I did so when I found that certain species had exceptional characteristics, but within very restricted limits. It seemed to me, however, that by multiplying the subgenera beyond measure, the confusion was increased rather than diminished. To remedy this, I have, in some subgenera, established unnamed sections, either geographical or based on morphological characters which are more-or-less constant."

(Key and text translated and edited by B. E. Boudinot, 14 February 2017.)

Note: 11 subgenera were not included in Emery's (1925) keys to the subgenera for various reasons: (1) he treated them as synonyms of other subgenera (Myrmopelta, Myrmotemnus), (2) he treated them as distinct genera (e.g., Dendromyrmex (Neotropical), Phasmomyrmex (Afrotropical), see Emery's (1925) key to the genera of the Camponotini for identification), (3) did not have material to study (Rhinomyrmex), or (4) they had yet to be described (Forelophilus, Myrmacrhaphe, Myrmespera, Myrmopalpella, Paramyrmamblys, Thlipsepinotus).

1

 * Tibiae strongly compressed, metatibiae short and blade-like, tarsi flat; head not depressed ... 2
 * Tibiae not or somewhat compressed; when compressed, head very depressed (C. (Myrmomalis) obtritus, Emery) (Plate 3, Fig 16, 16a) ... 3

2

 * Pronotum armed with anterolateral (humeral) teeth; dorsum of mesonotum through porpodeum produced as sharp, longitudinal ridge; metapleural spiracles visible from dorsal view on each side of ridge; large species ... Myrmepomis, Forel (38. Subgenus; "El Dorado ants")
 * Mesosoma without dorsal longitudinal ridge ... Myrmoplatypus, Santschi (37. Subgenus; "flat-leg carpenter ants")

3

 * Mesonotum and propodeum fused (metatonal-propodeal suture absent) and bearing dorsomedial carina with two unpaired spines, one anteriorly and one posteriorly; petiolar node with spines (Plate 3, Figure 15) ... Myrmodirachis, Emery (35. Subgenus; "stickle-back carpenter ants")
 * Mesosoma without medial carina ... 4

4

 * Antennae inserted remarkably distant from clypeus, in the middle or even behind middle of frontal carinae; caste dimorphism very pronounced; in American species (truncatus group) no intermediate castes are present between majors and minors; head of majors more-or-less cylindrical and obliquely truncate anteriorly, with truncated surface comprising only part of clypeus ... Colobopsis, Mayr (25. Genus [formerly subgenus]; "cork-head ants")
 * Antennae generally inserted in anterior half of frontal carinae; head of majors not truncate, or if it is, truncated surface generally includes all of clypeus ... 5

5

 * Head of majors strongly truncate; truncated surface includes most of anterior portion of head up to antennal insertions ... 6
 * Head of media, majors, and queens truncate or not; when truncate, truncated surface does not include anterior portion of head up to antennal insertions ... 7

6

 * Majors and queens with truncate surface of head in the of flattened or convex disc; scape, in repose, accommodated by scrobe (groove) along frontal carinae (Plate 3, Fig 10) ... Hypercolobopsis, Emery (30. Subgenus; "hyper false cork-head ants")
 * Truncated surface of head formed otherwise; furrow along frontal carinae lacking ... Manniella, Wheeler (29. Subgenus; "Mann's carpenter ants")

7

 * In general, in small and medium-sized workers, head short, wider posteriorly than anteriorly, with posterior head margin almost straight or slightly convex; eyes placed very posteriorly; caste dimorphism more-or-less pronounced: large workers or majors generally with short heads that have subparallel sides, rarely noticeably longer than wide; majors often with particular sculpture [sculpture form?] (P1.3, Fig.9, 9a); mesosoma short and broad, sometimes impressed or incised dorsally anterior to propodeum ... 8
 * In general, among small and medium-sized workers, head longer than that of large or major workers, with sides parallel and narrowed posteriorly (numerous exceptions to this rule exist, for example in subgenera Myrmaphaenus, Pseudocolobopsis, etc.); ordinarily eyes of minors not placed as posteriorly as above; caste dimorphism more-or-less pronounced; form of head of majors or soldiers extremely varied in different groups ... 10

8

 * Body flat, depressed; antennae and legs very long, tibiae compressed (Plate 3, Fig 16, 16a); color black; caste dimorphism poorly marked ... Myrmomalis, Forel (36. Subgenus; "flat carpenter ants")
 * With other character states ... 9

9

 * Dorsum of mesosoma bordered, propodeum also bordered and distinctly truncate posteriorly, with dorsal face extending as pair of flat teeth Myrmocladoecus, Wheeler (33. Subgenus; "rectangular carpenter ants")
 * Pronotum generally broad and flat, with sharp lateral edges; propodeum narrow and with variable form, bearing small unpaired and bifurcating spine in two species (Plate 3, Figure 14) ... Myrmeurynota, Forel (34. Subgenus; "pinch-neck carpenter ants")
 * Mesosomal dorsum continuous or interrupted, rounded or subbordered; propodeum rarely subbordered; caste dimorphism sometimes very pronouced, often little marked ... Myrmobrachys, Forel (32. Subgenus; "blocky carpenter ants")

10

 * Dorsum of mesosoma strongly impressed or incised anterior to propodeum; scapes and legs with fine, whitish setae; caste dimorphism pronounced ... Myrmosphincta, Forel (26. Subgenus; "corsetted carpenter ants")
 * Dorsum of mesosoma without impression, or when impression present, scapes and tibiae without standing setae ... 11

11

 * In majors and females, head elongate, with sides more-or-less parallel, generally obliquely truncate anteriorly, posterior head margin straight or emarginate; mesosomal dorsum arched, continuous; most of cuticle shining ... Pseudocolobopsis, Emery (28. Subgenus; "Western false cork-head ants")
 * With other character states: head of majors, soldiers, and females matte, at least when sides of head parallel ... 12

12

 * Clypeus without anterior lobe, anterior margin medially depressed or notched; head wide among major workers; mesosomal dorsum, anterior to propodeum, impressed or not ... Myrmentoma, Forel (12. Subgenus; "cleft-lip carpenter ants")
 * Mesosomal dorsum continuous, without impression anterior to propodeum ... 13

13

 * Head of majors, soldiers, and females in general, about same width anteriorly and posteriorly; in minor workers, anterior clypeal margin usually scalloped, or otherwise; scalloping along the anterior margin disappears as head becomes larger; in major workers, malar areas sink and become prominent, thus some species have convergent head shape of Colobopsis (C. salvini, Forel, silvestrii, Emery, etc.) ... Myrmaphaenus, Emery (27. Subgenus; "shining carpenter ants")
 * Head of workers and queens generally wider posteriorly than anteriorly; clypeus sometimes with anterior lobe; lobe usually rectangular or rounded, persisting on workers of all sizes … 14

14

 * Head of minors rounded posteriorly (not conical); scapes and legs with bristly, standing setae ... Myrmothrix, Forel (7. Subgenus; "bristly carpenter ants")
 * Scapes and legs with only appressed setae, otherwise head minors conical ... 15

15
Note: A number of species have been transferred from Camponotus sensu stricto to Tanaemyrmex since Genera Insectorum, particularly in North America.
 * Head of majors somewhat broader posteriorly than anteriorly; head of minors rounded posteriorly; clypeus with or without a short anterior lobe ... Camponotus, Mayr (4. Subgenus; "true carpenter ants")
 * Head of majors generally wider posteriorly than anteriorly; head of minors variable among species groups; clypeus usually more-or-less carinate and with pronounced anterior lobe ... Tanaemyrmex, Ashmead (5. Subgenus; "slim carpenter ants")