Camponotus edmondi species group

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Modified from: Rakotonirina J.C., Csosz S., and B.L. Fisher. 2016. Revision of the Malagasy Camponotus edmondi species group (Hymenoptera, Formicidae, Formicinae): integrating qualitative morphology and multivariate morphometric analysis. ZooKeys. 572:81-154. doi:10.3897/zookeys.572.7177

Malagasy Camponotus edmondi species group

Identification

In the Malagasy region, the C. edmondi species group can be differentiated from other species of the genus by the combination of the following characters: dorsolateral margin of propodeum marginate or extending into a sharp ridge, propodeal declivity usually concave, anterolateral corner of pronotum most often marginate, forecoxa larger than the width of mesopleuron, and usually the propodeal dorsum abruptly sloping down to the insertion of the petiole.

Key to Malagasy Camponotus edmondi species group

Diagnosis

Minor worker

1) Mandibles triangular, masticatory margins armed with 6 teeth; basal margins smooth.

2) Palp formula 6,4; palps long with respect to head size.

3) Clypeus with straight (C. ethicus, C. edmondi), broadly convex, or medially triangular (C. tafo) anterior margin in full-face view; median notch present in the posterior margin.

4) Antenna with 12 segments; pedicel longer than the flagellum, length gradually reduced towards the penultimate antennomere; apical portion of the flagellum either lighter or darker in color than the basal portion; antennal scape variable in length.

5) Base of antenna inserted a good distance from posterior margin of clypeus, the distance at least as large as the maximum width of antennal scape.

6) Frontal lobe narrow and partially covering the antennal insertion; frontal carina extended posteriorly at about the level of anterior margin of the eyes in full-face view.

7) Compound eye large, located anterior to the midline of the head in profile view.

8) Head longer than broad; broader posteriorly; posterior margin convex.

9) Pronotum broad with very short anterior face, anterodorsally marginate to carinate; dorsolateral portion slightly to strongly marginate anteriorly; anterior and lateral faces rounding to the dorsum in C. alamaina.

10) Promesonotal suture present.

11) Metanotal groove vestigial or slightly impressed (C. androy and C. bevohitra) to strongly impressed.

12) Metapleuron anteroposteriorly compressed between mesopleuron and propodeum.

13) Propodeum generally marginate dorsolaterally; in lateral view, most of the dorsum abruptly sloping down to the insertion of the petiole; propodeum quadrate (C. robustus), with a pair of triangular extensions posteriorly (C. ethicus and C. alamaina).

14) Propodeal declivity slightly to strongly concave.

15) Propodeal lobe absent.

16) Metapleural gland lacking.

17) Procoxa large, maximum width larger than width of mesopleuron (or at least as large as 2/3 the width of the mesopleuro-propodeal surface together).

18) Tibial spur single and pectinate on mesotibia and metatibia.

19) Petiole generally flattened anteroposteriorly except in C. echinoploides; in profile, anterior margin convex and posterior margin either convex or straight; both faces either rounding or tapering dorsally.

21) Sculpture ranging from smooth and shiny superimposed with microreticulation to densely and finely reticulate-punctate or reticulate rugose.

22) Body color varying from light brown to black with lighter gastral segment and even lighter appendages (brown to depigmented yellow).

Major worker

Most of the features mentioned above for the minor caste are also characteristics of the major caste, except that the latter has the following characteristics: a bigger head, roughly as long as broad in full-face view; lateral cephalic margins gradually narrowed or abruptly converging (C. echinoploides) to the base of mandibles; posterior margin more or less straight; both palps and antennal scape short with respect to head size; antennal scape not surpassing posterior cephalic margin; anterior clypeal margin more or less straight; pronotum broad in dorsal view; in dorsal view, metanotum a narrow transverse ridge between metanotal groove and propodeum.

Notes

Although the majority of species in the edmondi species group are arboreal (13/15), a few species are terrestrial (i.e., build their nests in the ground, in rotten logs, and in dead tree stumps). Sometimes individual workers are found foraging on the forest floor or through leaf litter. Within a colony, two very different worker castes, minor and major workers (see Fig. 3), are observed in the group; between these extremes, various worker forms showing continuous morphological variation occur. The combination of the following features can be used to reliably diagnose the two extreme worker castes relative to other Malagasy species groups.