Colobopsis macrocephala

Camponotus macrocephalus is generally found nesting in branches of trees and shrubs in eastern Australia.



Major and minor workers (images by Archie McArthur, SAM (Adelaide)).



A minor worker cleaning its antenna using a special structure on its front leg (image by Steve Shattuck).

Identification
Mandibles in major workers smooth, with shallow fovae, rugae weak and limited to anterior region of dorsal surface of the mandible. Few long, erect setae on head and gaster, none elsewhere. In lateral view, dorsal surfaces of pronotum, mesonotum and propodeum form a continuous weakly convex surface, the posterior propodeal face mostly straight.

Distribution
This taxon was described from Australia.

Nomenclature

 *  macrocephalus. Formica macrocephala Erichson, 1842: 259 (q.) AUSTRALIA. Combination in Iridomyrmex: Taylor & Brown, D.R. 1985: 100; in Camponotus: Shattuck & McArthur, 1995: 122. Senior synonym of fictor: Shattuck & McArthur, 1995: 122; of augustulus, semicarinata: McArthur & Shattuck, 2001: 38. See also: Shattuck, 1992a: 16.
 * semicarinata. Colobopsis rufifrons r. semicarinata Forel, 1895f: 418 (s.) AUSTRALIA. Combination in Camponotus (Colobopsis): Forel, 1902h: 508. Raised to species: Forel, 1902h: 508. Junior synonym of macrocephalus: McArthur & Shattuck, 2001: 38.
 * fictor. Camponotus (Colobopsis) fictor Forel, 1902h: 508 (s.w.) AUSTRALIA. Wheeler, G.C. & Wheeler, J. 1968: 217 (l.). Junior synonym of macrocephalus Erichson: Shattuck & McArthur, 1995: 122.
 * augustulus. Camponotus (Colobopsis) fictor subsp. augustulus Viehmeyer, 1925b: 145 (s.w.q.) AUSTRALIA. Material of the unavailable name continentalis referred here: Viehmeyer, 1925b: 145. Subspecies of macrocephalus: Bolton, 1995b: 87. Junior synonym of macrocephalus: McArthur & Shattuck, 2001: 38.

Description
Major worker. In lateral view. Yellow brown, gaster sometimes darker, limbs, especially coxa very much lighter than mesosoma. Head: Side with no erect setae, anterior sharply truncated; posterior glossy, smooth; anterior striations extending from truncation nearly half way to eye; vertex with few long setae; underside of head without erect setae, with very sparse short, flat-lying setae. Mesosoma: Without erect setae. Pronotum and Mesonotum: Evenly convex. Metanotum: Wide trough, spiracle well below dorsum. Propodeum: Dorsum evenly curved, angle rounded; declivity mostly straight; ratio dorsum/declivity, approximately 1; spiracle well forward of declivity, closer to coxa than dorsum, surrounded by indistinct reticulate integument, glossy, without pilosity. Node: Without setae, anterior face lower half straight, upper evenly convex; summit blunt; posterior face straight. Gaster: Glossy, indistinctly striate. Fore femur: Swollen. Mid tibia: Without erect setae, with sparse, flat-lying pubescence, without bristles inside. In dorsal view. Head: Nearly rectangular, sides straight, parallel; vertex straight, angles blunt; scape with very sparse, short, flat-lying setae. Frontal carinae mostly straight, diverging, posterior very wide. Frontal area, very small, depressed; clypeus sides bordered by sharp ridge, narrow, widest at truncation, sides nearly straight, tapering anteriorly, grossly ridged longitudinally, similar to cheeks, three fourths of clypeus anterior to truncation. Anterior head comprising clypeus, mandibles and cheeks lie on flat circular plane; max HW at eye centre; eyes oval. Clypeus: Without erect setae, carina present within striations; anterior margin narrow, projecting, evenly convex. In front or rear view. Node: Summit wide, slightly indented, without setae.

Minor worker. Head: Brownish yellow to brown, limbs and antennae more yellowish, much lighter than mesosoma; side of head, mesosoma, node yellow brown; vertex with few setae; underside of head without erect setae. Mesosoma: Glossy, microscopically reticulate, without pilosity. Pronotum: Anterior and posterior thirds straight, centre third convex. Mesonotum: Mostly straight, slightly raised above pronotum and propodeum. Metanotum: Slight ridge; spiracle near middle of side. Propodeum: Dorsum straight to flatly convex, angle abrupt; declivity nearly straight, ratio dorsum/declivity about 1.5; spiracle situated midway between dorsum and coxa, glossy, surrounded by microscopic reticulation. Node: Without pilosity, anterior face lower half straight, convex above; summit sharp; posterior face straight. Gaster: Finely striate. Fore femur: Swollen. Mid tibia: With indistinct, sparse, short, flat-lying setae, without bristles inside. In dorsal view. Head: Sides straight, slightly tapering to front; vertex and angles form even convexity; scape with indistinct, sparse, short, flat setae; frontal carinae wide, diverging; frontal area indistinct, diamond shaped; max HW just posterior to eye centre. Clypeus: Glossy, finely reticulate, few sparse, erect, setae, carina indistinct; anterior margin, convex, wide, projecting. In front or rear view. Node: Summit wide, sometimes indented, without setae.

Original descriptions

45(a) Camponotus fictor Forel,A. (1902).

Major. Length 6 to 6.7 mm. Head 1/3 longer than wide (1/5 in the case of semicarinatus) Clypeus feebly keeled, extending from one end of the clypeus to the other. The front of the head is clearly wrinkled lengthwise, not rugose (wrinkled-reticulate) in the case of semicarinatus.

QUEEN   Length 3.5 to 5 mm. Head elongated, almost a quarter longer than wide (almost square in the case of semicarinatus). In addition the head of the worker is not truncated in front, whereas in the case of semicarinatus it is at least as truncated (obtusely) as C truncatus queen of Europe; the difference is quite specific. The head of C fictor minor is like an ordinary Camponotus head,only the clypeus, is sub-keeled, a strong and rounded lobe which is almost absent in the case of carinatus. The thorax is as convex; the basal face of the metanotum (= propodeum) is longer than the declivity, terminating in a clear strong angle. The face of the declivity is a little concave and edged and ends in a point above the angle which projects even slightly. In semicarinatus, the declivity undergoes an abrupt but rounded curve at the basal face which is much shorter. The metanotum (= propodeum) of C fictor reminds one of C conicus Mayr while being much less accentuated. The node is a little thicker, strongly convex at front, flat at back, with a very sharp edge, slightly indented at the summit. In the case of semicarinatus it is much lower and much less thick. Sculpture (except for wrinkles at the front of the head) pilosity and color are identical with semicarinatus.

New Castle, Native Dog Bore N S Wales (Froggatt)

45(b) Formica macrocephala Erichson, W F. (1842).

Dark brown, gray-silky, elongated head, emarginate at the base, testaceous, pale legs.(Female) Length 5 lines.

Closely resembling F.cylindricae Latr., dark brown, sparse (grisea) silky pubescence. Head wider than the thorax, oblong with straight sides, emarginate at the base, the posterior angles are very prominent, punctations overall are feeble and a red brick color. Thorax narrowed, compressed, brick colored underneath. The node is small, low and subemarginate at the apex. The abdomen is rather long, very large and subdepressed dorsally. Legs are a pale brick color. The wings are elongate, transparent,stigmata dark brown,pale nerves, with 3 cubital cells anteriorally and a single discoidal cell.

46 Camponotus fictor augustulus Viehmeyer,H. (1925). C.(Colobopsis) victor augustulus n.sp.:(C.sommeri continentalus Viehm. in lit.)

Worker (major). The head is noticeable narrower than the type and less high, with mandibles included being a 1/4 longer than the width near the eyes, The truncate surface of the anterior head is even less sharply delineated and less concave than the type, the longitudinal grooves of the head and clypeus are much stronger. The scape just reaches the posterior border of the head (with the type it surpassed it by all least its greatest thickness). The thorax somewhat weaker, the angle of the epinotum is a little more rounded. In other respects like the type. Length 6-7.5 mm.

Worker (minor). The head is about 1/3 longer than wide. Anterior head only indistinctly truncate; clypeus wider to the front not narrowing, without a distinctly separated posterior piece. Eyes bigger the scape extends beyond the posterior border of the head by a segment (as with the type). Epinotum angle sharper, less rounded. Sculpture of the anterior head much weaker,also weaker than the type. Otherwise like the worker (major).Length 5.5 mm.

Worker. Head with the same length somewhat narrower than with the type; the scape protruding past the posterior margin of the head for only about 1/4 of its length (with the type about 1/3) Otherwise like the type. Length 4-5 mm.

Female,   as the worker major but the scape protruding over the posterior of the head. Mesonotum and posterior head finely reticulate and softly shining, epinotum angle strongly rounded, the node of the petiole thicker. Gaster segments with wide blackish brown connective tissue. Wings missing. Length 8.5mm. -- Nest in a dry branch of a forest tree near Trial Bay. The shape which because of the narrower head is also distinguishable from sommeri, is especially interesting because of the dimorphism of the soldier cast

Measurements
PW 1.0 mm, HT 1.2 mm, EL 0.4 mm, HW 1.4 mm, HL 1.8 mm, CAR W 0.8 mm, CLY W 0.6 mm, TL 0.9 mm, NW 0.55 mm.


 * CAR W = maximum frontal carina width
 * CLY W = clypeus width measured between tentorial pits
 * EL = eye length in dorsal view
 * HW = maximum head width in dorsal view
 * HT = maximum head thickness in lateral view
 * HL = head length measured from anterior margin of clypeus to vertex
 * PW = maximum pronotal width in dorsal view
 * NW = node width in dorsal view
 * TL = length of mid tibiae.

Taxonomy
Forel (1902) distinguished semicarinatus from macrocephalus (as fictor) by differences in the shape of the head, propodeum and petiolar node and in having the sculpturing on the truncated portion of the clypeus “more clearly lengthwise and not wrinkled-reticulate as in the case of semicarinatus.” Viehmeyer (1925) described the subspecies augustulus as having “head of the major worker noticeably narrower than in the type, the truncate surface of the anterior head less sharply delineated and less concave, and the longitudinal grooves of the head and clypeus much stronger”. However, the currently available material shows considerable variation in all of these characters and we can find no justification for recognising the subspecies separately from C. macrocephalus. For separation from the closely related C. howensis, see Remarks under that species.

Additional References

 * 🇦🇹 (1925). Hymenoptera. Fam. Formicidae. Subfam. Formicinae. Genera Insectorum. 183 : 1–302 [taxonomy, p. 272]
 * 🇦🇹 (1902). Fourmis nouvelles d'Australie. Revue Suisse de Zoologie. 10 : 405–548 [taxonomy, p. 508]
 * 🇦🇹 (2001). A taxonomic revision of the Camponotus macrocephalus species group (Hymenoptera: Formicidae) in Australia. Transactions of the Royal Society of South Australia. 125 : 25–43 [taxonomy]
 * 🇦🇹 (1995). Generic placements of Australian ants described by W. F. Erichson (Hymenoptera: Formicidae). Journal of the Australian Entomological Society. 34 : 121–123 [taxonomy, p. 121]
 * 🇦🇹 (1985). Formicoidea. pp. 1–149 in Walton, D. W. Zoological catalogue of Australia, vol. 2. Hymenoptera: Formicoidea, Vespoidea and Sphecoidea. Canberra : Australian Government Publishing Service. vi + 381 pp. [taxonomy]