Colobopsis

Historical note on Colobopsis with respect to Camponotus, Wheeler (1904):

"Since 1889 Colobopsis has been used to include those species of Camponotus which have sharply truncated heads in the soldier caste ... species in which the anterior truncated surface of the head in the major workers and the females is distinctly marginate and in which even the mandibles have a sharp external ridge separating an anterior from a latero-ventral face. In these species the head presents a peculiar sculpture consisting of umbilicate punctures ... and there is an absence of a cocoon in the pupal stages of all the phases."

Historical notes on Colobopsis ethology, Emery (1925):

"Ethology. - The species of Colobopsis, as well as many subgenera of Camponotus, live in wood, small and large dead branches, galls, etc., in which they carve galleries; the which open to the surface of the wood always have the exact diameter of the anterior truncation of the head of majors and queens. A soldier, or the queen, keeps custody over the nest, that is to say, she seals the hole with her head, and retires into the nest tunnel to allow sisters to pass. Towards this end, the gallery widens immediately within the hole, which means that the doorman (i.e., the soldier or guard) can give passage to sisters and immediately close the opening by means of its plug-shaped head. Many species of various Camponotus subgenera Myrmamblys, Myrmogonia [now synonymized with Colobopsis], Myrmaphaenus, etc., as well as lignicolous ants in general, have pronounced plug-like heads in the major workers, and are likely to have a soldier act as gatekeeper for the colony."

(Translation of Emery 1925 by B. E. Boudinot, 19 February 2017.)

Identification
Based on the dual phylogenies of Blaimer et al. (2015) which demonstrated that Colobopsis is sister to the remainder of the Camponotini, Ward et al. (2016) assiduously transferred all Colobopsis species out of Camponotus and proposed the following diagnosis for Colobopsis:

"Minor worker Generally small, HW 0.65–1.10 (exceptions: cylindrica group and the Fijian radiation, where HW 0.90–1.70), with rounded head and relatively small eyes, REL 0.20–0.32; head width three-quarters of more of head length (CI 0.75–0.98; except one Fijian species, C. polynesica, where CI ~0.72); antennal insertions—and hence also the frontal carinae—relatively relatively well separated, ASM/HW 0.36–0.47 (except cylindrica group, New Caledonia radiation and the Fijian radiation, where ASM/HW 0.31–0.39), ASM/CLW usually 0.66–0.98 (except some New Caledonian and most Fijian species where ASM/CLW is in the range of 0.60– 0.66); frontal carinae relatively short, usually not strongly sinuate, the antennal insertions occurring at about midlength of the frontal carinae; clypeus more or less subquadrate, as long as wide or slightly wider than long (CLW/CLL 0.96–1.32), with sides parallel or diverging moderately towards the anterior margin (clypeus broader in Fijian species of the bryani and dentata groups where CLW/CLL ~ 1.46, and in the conica and vitrea groups, sensu Emery (1925), where CLW/CLL 1.40–1.50 and clypeus more trapezoidal in form); anterolateral extremities of clypeus differentiated from rest of clypeus by a sulcus or impression running from the anterior tentorial pit to the clypeal margin, the suture between clypeus and malar region of head often weak here, so that the clypeus appears to lack the anterolateral extensions often conspicuous in Camponotus minors (compare Figures 2–5 with Figure 15).

Major worker Head generally phragmotic, varying from strongly truncate and marginate (Figure 6) to weakly truncate (Figure 7), the truncated portion incorporating part of the clypeus, the malar region of the head capsule and the upper surface of the mandibles. Clypeus elongate-rectangular, the anterolateral extremities separated from the clypeus by a well-marked sulcus and appearing to form an independent triangular sclerite.

Additionally: Dimorphic worker caste, with few or no intermediates between major and minor workers, except in the cylindrica group (Emery 1925); larva with distinctive ventral trough (praesaepium), overhung posteriorly by a protruding welt of the second abdominal segment (Wheeler & Wheeler 1953, 1982); pupa naked (Wheeler 1904). Brendon Boudinot has recently found that male Colobopsis have distinctive genitalia,with the shape of the digitus distinguishing them from Camponotus males (Boudinot, in prep.)."

Distinguishing Colobopsis from Camponotus
To differentiate Colobopsis from Camponotus Ward et al. (2016) proposed the following global key:

1 Not occurring in Fiji or New Caledonia ... 2

- Occurring in Fiji ... 3

- Occurring New Caledonia ... 4

2 Generally small species, HW 0.65–1.10 (except cylindrica-group of Southeast Asia with HW 1.20–1.70, and facies as in Figures 4 and 5); either antennal insertions relatively well separated, such that ASM/HW 0.36–0.47 and ASM/CLW 0.66–0.98, and/or clypeus relatively narrow, such that CLW/CLL 0.96–1.32; antennal insertions occurring at about midlength of frontal carinae; anterolateral extremities of clypeus set off from rest of clypeus by a sulcus or impression, so clypeus appears to lack prominent anterolateral extensions (Figures 2–5) ... Colobopsis

- Small to large species, HW 0.70–3.00; antennal insertions less well separated, such that ASM/HW 0.22–0.35 and ASM/CLW 0.35–0.68; clypeus variable in shape but in smaller species with HW 0.70–1.35 (e.g., Camponotus (Myrmamblys), C. (Myrmentoma) and C. (Pseudocolobopsis)) clypeus tending to be relatively broad, such that CLW/CLL 1.25–1.62, although exceptions occur (e.g., in some C. (Pseudocolobopsis) species) (Figures 14–15); antennal insertions usually occurring in front of midlength of frontal carinae; clypeus typically with prominent anterolateral extensions (Figure 15) ... Camponotus

3 With conspicuous long setae, gracile legs, and a shield-shaped clypeus with prominent anterolateral extensions (Figure 16) ... Camponotus chloroticus

- Without the combination of conspicuous long setae and gracile legs; clypeus lacking prominent anterolateral extensions (Figures 8–11) ... Colobopsis

4 Small species, HW 0.68–1.04; antennal insertions more widely separated (ASM/HW 0.34–0.39 and ASM/CLW 0.64–0.77) (Figures 18–19); clypeus tending to be less broad (CLW/CLL 1.15–1.40) ... Colobopsis

- Small to medium-sized species, HW 0.75–2.10; antennal insertions less well separated (ASM/HW 0.25–0.29 and ASM/CLW 0.46–0.55); clypeus varying in shape, but if HW < 1.05 (e.g., Camponotus pulchellus complex) (Figure 17) then clypeus tending to be broader (CLW/CLL 1.25–1.60) ... Camponotus

Distribution
Ward et al. (2016) - Colobopsis occurs in the New World from southern United States to Costa Rica; across the southern and central Palearctic from the western Mediterranean to Japan; throughout the Oriental and Australian biogeographic regions as far south as Tasmania; and into the Pacific as far east as New Caledonia, Vanuatu, and Fiji. The genus is notably absent from the Afrotropics and most of the Neotropics.

Fossils
Fossils are known from:.

Biology
Ward et al. (2016) - Most species of Colobopsis are strictly arboreal, nesting in cavities in dead branches or twigs and employing phragmotic major workers to block the nest entrance (Forel 1892; Wheeler 1904; Creighton 1967). In some Fijian species, with reduced phragmosis, nests can also be found in rotten wood and in epiphytic ant-plants (Sarnat & Economo 2012). Phragmosis is also reduced in some Southeast Asian species nesting in live stems; at least one species, Colobopsis macarangae, apparently lacks a major worker subcaste (Dumpert 1996). In the field, collections of Colobopsis can be readily distinguished from those of Camponotus if pupae are available: these are always naked in Colobopsis (Wheeler 1904; Ward, pers. obs.), while those of Camponotus are enclosed in cocoons.

The Colobopsis cylindrica group employs a novel defensive strategy. Minor workers of these so called exploding ants will, when threatened, flex their gasters so hard that they rupture. This releases a toxic chemical mixture that they then attempt to smear on their antagonists.

Castes
Major and minor castes, majors with phragmotic heads.



Nomenclature

 *  COLOBOPSIS [subgenus of Camponotus]
 * Colobopsis Mayr, 1861: 38. Type-species: Formica truncata, by subsequent designation of Bingham, 1903: 342.
 * Colobopsis subgenus of Camponotus: Emery, 1889b: 517.
 * Colobopsis senior synonym of Condylomyrma: Wheeler, W.M. 1934e: 422 (in text).
 * Colobopsis senior synonym of Dolophra: Bolton, 2003: 113, 268.
 * CONDYLOMYRMA [junior synonym of Colobopsis]
 * Condylomyrma Santschi, 1928c: 72 [as subgenus of Camponotus]. Type-species: Camponotus (Condylomyrma) bryani, by monotypy.
 * Condylomyrma junior synonym of Colobopsis: Wheeler, W.M. 1934e: 422 (in text).
 *  CAMPYLOMYRMA [unavailable name]
 * Campylomyrma Wheeler, W.M. 1934e: 421, incorrect subsequent spelling of Condylomyrma: Bolton, 1995b: 23.
 * MYRMOTEMNUS [junior synonym of Colobopsis]
 * Myrmotemnus Emery, 1920b: 246 [as subgenus of Camponotus]. Type-species: Camponotus moeschi, by original designation.
 * Myrmotemnus junior synonym of Myrmamblys: Wheeler, W.M. 1921a: 19; Wheeler, W.M. 1922a: 708; Emery, 1925b: 137.
 * Myrmotemnus revived status as subgenus of Camponotus: Santschi, 1926c: 601.
 * Myrmotemnus junior synonym of Colobopsis: Ward & Boudinot, 2021: 41.