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

KEY TO THE SUBGENERA OF CAMPONOTUS FOR THE OLD WORLD, INCLUDING AUSTRALIA

Below is Emery's (1925) key to the subgenera of Camponotus for the Old World, including Australia. 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 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

Masticatory mandibular margin with some teeth scalloped (i.e., with more than one point); basal mandibular margin also dentate; clypeus carinate, produced anteriorly as a strong lobe, medially notched, and furnished anterolaterally with horn-like angles (Plate 2, Fig. 16). Giant Malaysian species ... Dinomyrmex, Ashmead (1. Genus [formerly subgenus]; "terror ants")
Mandibles with simple teeth (i.e., with single point), basal mandibular margin generally edentate; clypeus variable ... 2

2

Clypeus, mandibles, and prementum with conspicuous psammophores: clypeus with transverse row of setae set near posterior clypeal margin, forming a “mustache”; mandible with row of setae on dorsal and medial margins; prementum with basal tuft of setae (Plate 2, Figure 18). African species ... Myrmopsamma, Forel (3. Subgenus; "mustachioed carpenter ants")
Psammophores absent ... 3

3

Apical mandibular tooth very long and masticatory margin very oblique (Plate 2, Fig.17); minor workers with postocciput exposed with head in dorsal view. Large African species. Queens with mandibles similar to the worker ... Myrmoxygenys, Emery (2. Subgenus; "imperial carpenter ants") (note: major worker unknown, possibly non-existant, see p. 504)
Apical mandibular tooth much shorter; minor workers with postocciput obscured by vertex or occipital ridge in dorsal view. Size variable … 4

4

Antennae inserted at or approximately at midlength of the frontal carinae ... 5 (note: at least one Myrmoplatys species with antennae inserted anterior to midlength)
Antennae inserted in anterior half of frontal carinae ... 7

5

Majors and minors with anterior half of head depressed; antennomeres of funiculus remarkably short... Myrmoplatys, Forel (21. Subgenus; "flat-head carpenter ants")
Anterior half of head not depressed; dimorphism extremely marked; in soldiers and females, the head is more or less cylindrical and obliquely truncate anteriorly, such that in general the surface of the truncation comprises only part of the clypeus (Plate 3, Figure 8, Sa) ... 6

6

Dorsum of mesosoma continuous or interrupted by impressions or notches; propodeum not compressed as a blade, rarely armed with paired teeth ... Colobopsis, Mayr (25. Genus [formerly subgenus]; "cork-head ants")
Mesosoma tall and strongly compressed; propodeum raised and blade-like, often extended posteriorly as an unpaired tooth ... Myrmogonia, Forel (Synonym of Colobopsis [Emery's Camponotus subgenus 24]; "crest-back cork-head ants")

7

Mesosoma narrow, with constriction at about midlength which represents the mesonotum and metanotum, which are very elongated; propodeum raised above metanotum and shaped like a rounded bump. Malagasy species (Plate 3, Figure 6) ... Myrmopytia, Emery (10. Subgenus; "supermodel carpenter ants")
Mesosoma not or only somewhat constricted ... 8

8

Without caste dimorphism; head, in full-face view, round and wider posteriorly than anteriorly; mesosoma lacking margination and deeply impressed anterior to propodeum; clypeus very short, without a lobe, and sometimes medially notched. Indomalayan species ... Karavaievia, Emery (11. Subgenus; "Asian weaving carpenter ants") => see keys to Karavaievia species based on workers, queens, and males
Dimorphism more-or-less pronounced (in a group from Madagascar the dorsum of the mesosoma is bordered and caste polymorphism is somewhat pronounced) ... 9

9

Tibiae and scapes compressed and bearing bristly, standing setae; aroliae of forelegs bearing thick brushes of hair (BEB note: I have not been able to meaningfully observe this). Large and medium Malaysian species ... Myrmotarsus, Forel (20. Subgenus; "flat-foot carpenter ants")
With other character states ... 10

10

Body generally massive; head of minors usually short, wider posteriorly than anteriorly, with posterior head margin straight or slightly convex, and eyes set posteriorly; head of majors usually broad, much more narrow anteriorly (Plate 3, Fig. 7, 7a); mesosoma generally short, pronotal disc always shouldered and marginate or submarginate, In some groups, a more-or-less deep impression separates the propodeum from other mesosomal segments, which is then usually marginate or even bidentate. African, Malagasy, and Indian species ... 11
With other character states. In some Australian species, minor workers have heads as previously stated [???] ... 15

11

Petiole broadly nodiform and low, with conspicuous, coarse punctation; mesosoma more-or-less impressed anterior to propodeum; propodeum usually marginate and sometimes bidentate; pronotum rarely shouldered and bidentate ... Orthonotomyrmex, Ashmead (15. Subgenus; "flat-back carpenter ants")
Petiole squamiform, never nodiform, and scale thin or thick ... 12

12

Head of major with anterior areas (e.g., malar area, genae, etc.) riddled with distinct foveae which are punctate inside ... 13
Head of major worker without foveate-punctation ... 14

13

Pronotum depressed and marginate; propodeum marginate ... Myrmisolepis, Santschi (19. Subgenus; "angular acne ants")
Propodeum without margination ... Myrmotrema, Forel (18. Subgenus; "rounded acne ants")

14

Petiolar scale more or less thick, sometimes very broad and massive; mesosoma generally impressed anterior to propodeum, propodeum marginate or sometimes bidentate; in other cases, propodeum very short and sloping downwards (C. echinoploides) (Plate 3, Fig. 6). Body black; cuticle matte ... Myrmepinotus, Santschi (16. Subgenus; "box-back carpenter ants")
Petiolar scale generally thin, with edges more or less sharp; dorsum of mesosoma continuous or impressed; propodeum rarely marginate; cuticle matte, punctate; often with coarse, tawny, yellow, or white setae, setae scattered and often serrate, forming a characteristic fur-like coat ... Myrmopiromis, Wheeler (17. Subgenus; "furry carpenter ants")

15

Head of the major worker massive, notched behind, narrowed anteriorly; head of the minor worker rounded posteriorly and forming a more or less distinct collar which articulates with the mesosoma; clypeus with an anterior lobe which is usually rounded; mesosoma posteriorly elongate, completely lacking margination, more or less depressed in as a saddle or impressed along the metanotal-propodeal suture (Plate 2, Fig 15). Indomalayan, Australian, and Malagasy species ... Myrmosaulus, Wheeler (9. Subgenus; "monster-head carpenter ants")
With other character states ... 16

16

Medial portion of the clypeus of majors (between anterior tentorial pits) reduced in width compared with that of minors, and with respect to the malar area, which are often more prominent; minors often with medial clypeal carina and anterior lobe, majors with carina and lobe reduced or effaced. Caste dimorphism sometimes extreme ... 17
Clypeus varying in form and proportion in relation to the size of the head in both minors and majors, except usually the size and shape of the anterior lobe, which is usually present … 18

17

Head of major workers usually longer than wide; in many species, the head is variably sculptured and more or less distinctly truncate or obtuse anteriorly, with parallel sides (having the facies of Colobopsis); clypeus variable, usually without anterior lobe, or produced as arc, rarely with narrow lobe (some species of Africa: C. emarginatus, C. nasutus). Old World and Australia ... Myrmamblys, Forel (20. Subgenus; "Eastern false cork-head ants")
Head of majors broad, neither truncate nor obtuse anteriorly; clypeus without anterior lobe, but with anterior margin medially depressed or narrowly incised; dorsum of mesosoma impressed anterior to propodeum. Holarctic and Asian species... Myrmentoma, Forel (12. Subgenus; "cleft-lip carpenter ants")
Head of major worker usually broad and vaulted; clypeus arched or lobed anteriorly in minors; anterior clypeal lobe reduced in majors, and is displaced medially, such that anterior border is more-or-less distinct; anterior clypeal margin bidentate … Myrmophyma, Forel (8. Subgenus; "bladder-head carpenter ants")

18

Dorsum of mesosoma more-or-less submarginate and interrupted by impressions at sutures; dimorphism only somewhat pronounced. Malagasy species ... Myrmonesites, Emery (14. Subgenus; "Malagasy hump-back carpenter ants")
Dorsum of mesosoma not at all marginate, except pronotal disc of the pronotum, which is rarely submargine anteriorly ... 19

19

Medium-sized species of Madagascar and Africa, cuticle glossy, head usually broad in majors; in these cases, clypeus usually bearing short lobe which is anteriorly truncate, or effaced, or becoming rounded in minor workers; mesosomal profile variable, continuous and vaulted, or with saddle-like propodeum, or propodeum lower than the mesonotum. ... Mayria, Forel (15. Subgenus; "Mayr's carpenter ants")
Species from Africa, the Mediterranean or India. Clypeus lobate; caste dimorphism often pronounced; head of minors sometimes very narrow (Plate 3, Fig. 3); body matte, finely sculptured and covered with pubescence (especially gaster) ... Myrmosericus, Forel (6. Subgenus; "silky carpenter ants")
With other character states ... 20

20

Caste dimorphism more-or-less pronounced; head of majors generally much wider posteriorly than anteriorly; head of minors variable; in a few groups, the head narrows as a cone or otherwise posteriorly, so that it has no further posterior margin (Plate 3, Fig 1, I a, I b, I c, 2); clypeus distinctly lobate ... Tanaemyrmex, Ashmead (5. Subgenus; "slim carpenter ants")
Head major workers somewhat broader posteriorly than anteriorly; head of minors with posterior margin more-or-less rounded (never forming cone); clypeus usually without anterior lobe or with only a short lobe ... Camponotus, Mayr (4. Subgenus; "true carpenter ants")

Note: A number of species have been transferred from Camponotus sensu stricto to Tanaemyrmex since Genera Insectorum, particularly in North America.

References

Emery, C. 1925d. Hymenoptera. Fam. Formicidae. Subfam. Formicinae. Genera Insectorum 183: 1-302.