Camponotus nigriceps species group

Based on Adams and MacArthur, 1996.

Species

Identification

A key to species of this group begins at couplet 33, Key to Camponotus of Australia (from MacArthur 2007).

It is necessary to emphasize that for accurate identification of these species, the key requires that both major workers as well as minor workers be available for examination. Although both major and minor workers may be taken with certainty from nests, the probability of taking major workers at a distance from the next is low. Thus, this key may not be completely satisfactory to the field biologist attempting to identify a catch from pitfall traps installed outside the range of major workers. Nevertheless, the use of the characters listed in the Table in conjunction with the key should allow researchers to identify workers from all castes in most circumstances.

Diagnosis

Workers In dorsal view, median anterior of clypeus projects forward; lateral margins never convex, varying from strongly concave in major workers to straight in minor workers; anterior comers always distinct (like teeth), varying from tapering outwards in major workers to tapering forward in minor workers; anterior margin of projection always concave, varying from V-shaped at centre in major workers to even and feebly concave in minor workers. Mandibles furnished with 6 teeth on masticating border, emargination occasionally lacking between proximal tooth and next shown dotted (never with a half tooth at proximal border as in Figure. Ventrum of pedicel pilose, convex (viewed from the side). Head width always greater than pronotum. Head sides in dorsal view: medium workers rounded, minor workers parallel except in smallest minors of Camponotus eastwoodi. Antennae attached to head capsule at a distance from clypeus, distance being greater than diameter of antenna! fossae. Tentorial pits distinctly depressed. Profile (viewed from the side) of that part of mesosoma, comprising pronotum, mesonotum, dorsum (=base) of propodeurn and upper three-fourths of declivity of propodeum (proximal to dorsum) never concave except when rnetanotum is present; feeble concavity may occur between mesonotum and propodcum. Profile of the node (viewed from side), anterior face convex, summit sharp. Integument finely reticulate overall, never hidden by pubescence except sometimes on appendages. Midtibiae with a coat of short setae or pubescence, inclination varying from adpresscd up to about 80°, length never exceeding 0·1 mm; with 2 rows of straight barbs on inner surface about 0-15 mm in length. Long setae on pronotum generally inclined forward; long setae on the gaster generally inclined backwards. Lacking 'J' shaped setae attached to the ventrum of head capsule (distinct from C. testaceipes, which possesses 5-10 setae). Polymorphic, head widths display dimorphism.

Notes

Emery (1925) proposed 34 subgenera and many subsubgenera for the world. One of Emery's subgenera was '11 me. Groupe nigriceps' which comprised eight named forms from Australia possessing a clypeus that was 'deeply notched in the middle of its anterior border'. The character is so distinctive that Emery's nigriceps group is generally accepted as a natural grouping within Camponotus, although this has yet to be confirmed by modern cladistic methods. Although species can be readily assigned to the C. nigriceps group, commonly called sugar ants in Australia (Froggatt 1905), it has until now been difficult to identify species within the group to any degree of certainty.

Usually forage nocturnally, occasionally on overcast days. Nests in soil, frequently under logs, stumps or stones.

Additional Resources

Camponotus
Tanaemyrmex

References

McArthur, A. J. and M. Adams. 1996. A morphological and molecular revision of the Camponotus nigriceps group (Hymenoptera: Formicidae) from Australia. Invertebrate Taxonomy. 10:1-46.
McArthur, A. J. 2007. A key to Camponotus Mayr of Australia. Pages 290-351 in Snelling, R. R., B. L. Fisher and P. S. Ward. Advances in ant systematics (Hymenoptera: Formicidae): Homage to E.O. Wilson - 50 years of contributions. Memoirs of the American Entomological Institute, vol. 80.