Genera Insectorum: Emery's key to Camponotus subgenera
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 worlds, are included in both keys.
In the first key, leads (= lugs) 10 and 16 may challenge the identifier, especially if only small 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 American 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 the beginning myrmecologists will be daunted by the considerable number of subgenera and by the weakness of their characters. The latter issue might have been gained precision by providing more divisions, as mentioned. I did so when I found that certain species had exceptional characteristics, but within very restricted limits. It seemed to me that, by multiplying the subgenera beyond measure, the confusion was increased rather than diminished. On the other hand, I have, in the subgenera, established unnamed sections, either geographical or based on morphological characters which are more-or-less constant.
(Translated and edited by B. E. Boudinot, 14 February, 2017.)