Camponotus grandidieri species group

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Modified from: Rakotonirina, J.C., Csosz, S., Fisher, B.L. 2017. Taxonomic revision of the Malagasy Camponotus grandidieri and niveosetosus species groups (Hymenoptera, Formicidae) using qualitative and quantitative morphology. Zootaxa 4238: 203–245 (DOI: 10.11646/zootaxa.4238.2.2).

Camponotus grandidieri species group

Key to Malagasy Camponotus grandidieri and niveosetosus species groups

Notes

The Camponotus grandidieri species group can be globally recognized by the combination of the following characters: straight anteromedian clypeal margin, which is not projecting anteriorly into a triangular lobe; clypeus without median longitudinal carina; with mesosoma in dorsal view, humeral angle rounded and not protruding anteriorly into a tubercle; propodeum tapering dorsally; sculpture of the gena and at least the anterior half of the head capsule for the major workers is superimposed with two to seven smaller areoles embedded in scattered larger punctures. The grandidieri species group is known to occur across the Afrotropical and the Malagasy regions.

Shared morphological traits of the Camponotus grandidieri and niveosetosus species groups of the Malagasy region

Members of the Camponotus grandidieri group and the C. niveosetosus group, as in the case of most Camponotus, present two different worker castes, minors and majors. In addition, various worker forms show continuous morphological variation between these castes. To distinguish both species groups from all other Malagasy Camponotus, using workers of either caste, the following combination of characters can be used:

1) Mandible triangular, basal margin shorter than apical margin, which is armed with six teeth.

2) Palp formula: 6,4. Maxillary palp long.

3) Head elongate in full-face view, lateral borders slightly diverging posteriorly; posterior border more or less convex. Lateral cephalic margins start rounding at posterior fifth of head, while in Mayria this rounding starts at posterior third of head. In the grandidieri group, the posterior section of the head appears angulate and in Mayria the posterior portion of the head looks more rounded.

4) Clypeus transversely trapezoidal. Clypeus with angulate anterolateral portion and straight anterior margin in grandidieri group; anteromedian margin slightly projecting into triangular lobe in niveosetosus group.

5) Antenna with 12 antennomeres; flagellomeres longer than broad and gradually decreasing in length towards the apex.

6) Antennal scape long, roughly its apical third to distal portion extending beyond posterior margin of the head.

7) Frontal lobe narrow anteriorly, wider at midlength and partially concealing the antennal insertion; frontal carinae becoming narrower posteriorly at level of anterior margin of eyes.

8) Compound eye large and protruding, sometimes breaking the outline of lateral cephalic margin, located from roughly posterior fourth to posterior sixth of the head. Compound eyes located from posterior fourth to posterior sixth of the head.

9) Mesosoma in lateral view, with broadly convex promesonotum; widest at level of pronotum in dorsal view.

10) Promesonotal suture visible.

11) Pronotum with rounded humeral angle, which is not projecting anteriorly; no sharp margination between pronotal dorsum and lateral portion. Pronotum anterodorsally marginate with a protruding humeral angle in Myrmopiromis, but in the grandidieri and niveosetosus species groups the humeral angle is rounded.

12) Mesopleuron and propodeal surface together distinctly longer than lateral portion of pronotum in lateral view.

13) Propodeal lobe lacking.

14) Metapleural gland absent.

15) Procoxa of normal size, maximum width as large as the width of mesopleuron. Maximum width of procoxa as large as width of mesopleuron; in Myrmepinotus (edmondi species group) procoxa is larger than width of mesopleuron.

16) Tibial spur single on mesotibia and metatibia.

17) Petiolar node generally compressed anteroposteriorly. Petiolar node tapering dorsally except in C. efitra and C. maintikibo, anterior face rounding to posterior face with short dorsal margin.

18) Sculpture of body dorsum ranging from finely and densely reticulate punctate to finely and densely imbricate; lateral portion from finely areolate to finely coriarious. Gastral tergites sometimes finely and densely strigulate. Most of the species of the Malagasy Camponotus have a smooth and shining integument, except the members of the edmondi species group and the subgenus Myrmopiromis.

19) Whitish, erect hairs on dorsum of head and body. Erect hairs slender and pointed on head, pronotum and anterior portion of mesonotum; thicker, stout and blunt or spatulate on propodeal dorsum, petiolar node, and anterior section of gastral tergites. In the grandidieri and niveosetosus groups, the erect hairs are thicker and their tips are split into two points; the distance between the two closest hairs is larger than half of the length of the longest hairs; the members of other subgenera have fewer erect hairs (e.g. Mayria); in the typical Myrmopiromis the distance between two closely spaced hairs is smaller than half of the length of the long hairs.

20) Pubescence present, short or long, sparse or abundant. Pubescence is as plentiful or more plentiful than the erect hairs in the groups studied in the present contribution, and less abundant than erect hairs in typical Myrmopiromis ants.

21) Major worker similar to minor worker, but characterized, in addition to the larger head and mesosoma, by the following distinctive traits: lateral portion of head particularly sculptured as finely and densely reticulate punctate, imbricate or areolate, and superimposed with two to seven smaller areoles embedded in scattered large punctures, from which an appressed hair arises medially; antennal scape shorter, its apex barely surpassing or not extending beyond posterior cephalic margin.

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