Camponotus Emery subgenera key

Emery (1925) recognized 38 subgenera within Camponotus and provided keys to the subgenera of the Old and New World. As some of the taxa currently considered to be subgenera of Camponotus were treated as distinct genera by Emery, it is worth studying his key to the genera of the Camponotini:

Emery's (1925) key to the genera of Camponotini based on workers and soldiers.

Note: Parenthetical numbers refer to the original taxon account order in Emery's contribution to Genera Insectorum (Emery 1925), while the rank indicates current taxonomic opinion.

(Key translated and edited by B. E. Boudinot, 18 February 2017.)

1
Metathoracic spiracles situated dorsally; scapes very long, greatly surpassing posterior head margin in repose, same with major workers; caste dimorphism punctuated with respect to head size … Notostigma, Emery (2. Genus) [note: transferred to Melophorini by Ward et al. (2016)] - Metathoracic spiracles situated laterally, rarely at dorsum (some Camponotus); scapes shorter, not greatly exceeding posterior head margin in minor workers … 2

2
Without caste dimorphism; metanotal dorsum anteroposteriorly long; petiolar node armed with well-developed to rudimentary spines. Afrotropics … Phasmomyrmex, Stitz (3. Subgenus) [note: Phasmomyrmex as subgenus of Camponotus, Ward et al. (2016)] - Metanotum generally fused with mesonotum, or appearing, among major workers, to form straight margin with propodeum … 3

3
Frontal carinae wide-set and strongly divergent posteriorly; eyes very large, placed at posterolaterally on head … Opisthopsis, F. Smith (1. Genus) - With different combination of characters … 4

4
Without dimorphism, head obtusely truncate anteriorly; antennal flagellum strongly increasing in size apically … Overbeckia, Viehmeyer (4. Genus)

- Flagellum filiform … 5

5
Abdominal segment III (gastral segment I) only somewhat wider than long; exceptionally, spines or denticles present on mesosoma or petiole … 6

- Abdominal segment III much longer than wide, covering most of gaster; generally with spines or denticles on mesosoma or petiole; without dimorphism … 8

6
Without dimorphism; body stout; head large, truncate posteriorly; mesosomal dorsum depressed, sutures clearly visible; petiole nodiform; abdominal segment III more-or-less distinctly longer than wide; color of cuticle often metallic. Australia … Calomyrmex, Emery (7. Genus)

- With different combination of characters … 7

7
Without dimorphism; head oval, somewhat elongated as neck. Neotropical … Dendromyrmex, Emery (6. Subgenus) [note: Emery considered Dendromyrmex to be a distinct genus]

- Caste dimorphism more-or-less apparent, sometimes extreme, rarely absent; head variable, often as in Calomyrmex, but only in minors. Variable, cosmopolitan species … Camponotus, Mayr (5. Genus)

8
Promesonotal suture distinct, meso-propodeal suture often effaced … 9 (Polyrhachis)

- Promesonotal suture obliterated or indistinct; abdominal segment III nearly completely covering gaster; body massive … 10 (Echinopla)

9
Mesonotum sunk into cleft between pronotum and metanotum. Sri Lanka … Hemioptica (9. Subgenus) [note: considered by Emery to be a distinct genus]

- Mesosoma not matching previous description; sutures distinct on dorsum, or meso-propodeal suture effaced; mesosoma and petiole generally armed with teeth or spines … Polyrhachis, F. Smith (8. Genus)

10
Petiole short and more-or-less large, armed laterally with teeth or a pair of spines; meso-propodeal suture generally impressed, rarely obsolete (E. praetexta, F. Smith) … Echinopla, F. Smith (10. Genus)

- Petiole voluminous and massive, unarmed; mesosomal dorsum without sutures … Mesoxena, F. Smith (11. synonym of Echinopla) [note: considered by Emery to be a distinct genus]