Taxonomic history
Stitz, 1938 PDF: 119 (q.).Combination in Camponotus (Myrmophyma): Emery, 1925d PDF: 110.Combination in Camponotus (Thlipsepinotus): Santschi, 1928e PDF: 483.Senior synonym of Camponotus aureopilus velutinus: Shattuck, 2005 PDF: 4.Camponotus is the world's largest and most widespread ant genus. It contains over 1500 described species and subspecies (Bolton 1995) and occurs in essentially all terrestrial habitats where ants are found. Individual species range in size from moderately small to large, and from highly abundant and visible to rare and cryptic. The genus is certainly one of nature's great success stories.
The species examined here form a small group of distinctive species limited to Papua New Guinea and neighboring Queensland, Australia. They share a number of characters (see below) suggesting a close relationship, and one of them ( C. thadeus , new species ) is only the second species in the genus with a metapleural gland. This gland, one of the autapomorphies uniting the family Formicidae, has been lost in a handful of genera (Bolton 2003) including all but two known species of Camponotus ( C. gigas and C. thadeus ). While C. gigas is morphologically unusual for the genus (and is currently placed in the monotypic subgenus Dinomyrmex (Bolton 1995)), C. thadeus is very similar to the other species considered here, suggesting an independent reversal in the loss of this gland. Clearly a detailed phylogenetic analysis will be required to address this hypothesis critically, an undertaking well outside the current study.
These appear to be rare ants with most species known from very limited material or occurring in very limited geographic areas (in the case of C. thadeus ). This currently restricts our ability to assess intraspecific variation as would be possible if additional material were available. However, the characters used in this study are based on those found to be useful in recognizing species of this genus occurring in Australia where extensive collections have been made and intraspecific versus interspecific variation can be assessed in detail (for example, Shattuck and McArthur 2002). A conservative approach has also been taken, with "solid" differences needed for species recognition. It is hoped that these factors will combine to provide a solid foundation for the taxonomy of these ants. Having said that, it is extremely likely that this study represents only a small fraction of the taxa occurring in this species-group and additional collecting in Papua New Guinea and eastern Indonesia will undoubtedly reveal many more species.
Members of this species-group can be separated from most other species in the genus, and from all Old World species, by having either or both of the following characters: (1) head with an angle, ridge or strong inflection line running between the compound eye and the posterolateral corner, the area immediately below this ridge varying from weakly to strongly concave (Fig. 6); (2) the presence of numerous enlarged, closely spaced, elongate, finely barbed white or yellow hairs on the dorsum of the pronotum, mesonotum and/or gaster (Figs 24, 25). These hairs are found in dense groups and are present in all species with the exception of cyrtomyrmodes (in this species the posterolateral section of the head is strongly ridged dorsally and concave laterally). When present, these hairs will immediately identify these taxa among Old World Camponotus . A few New World species in the subgenera Manniella , Myrmaphaenus and Myrmeurynota share these characters (for example, C. personatus and C. sphaericus ), but there is no evidence of close phylogenetic relationship between these two sets of taxa.
Donisthorpe (1936, 1941a, b), who described three of the species treated here, placed his species in the subgenus Myrmophyma and, as noted below, Emery (1925) considered aureopilus as belonging here as well. This is a South-east Asian and Australian subgenus containing just over 30 species (Bolton 1995). While not currently defined in any rigorous manner, all species share a similar head shape (straight-sided and either parallel or converging anteriorly) and either a compact, highly arched mesosoma (as in the aureopilus group) or an elongate body with a low propodeum (as in ephippium (Smith) and relatives).
Key to species of the Camponotus aureopilus Group based on major and minor workers
1. Dorsum of mesosoma with fewer than 6 scattered hairs and lacking patches of enlarged hairs (Figs 5, 6); anterolateral pronotum projecting as a narrow ridge (Fig. 4)
................................................................................................................ cyrtomyrmodes
- Dorsum of mesosoma and/or gaster with at least a small patch of enlarged hairs (Fig. 9); anterolateral pronotum rounded, not ridged (Fig. 1) ............................................... 2
2. Metapleural gland present above the hind leg (Figs 24, 26); enlarged hairs on dorsum of mesosoma bright yellow (Figs 23, 24) (Australia)......................................... thadeus
- Metapleural gland absent (Fig. 9); enlarged hairs on dorsum of mesosoma white (Figs 14, 15) or pale yellow-white (Figs 8, 9) (Papua New Guinea).....................................3
3. Enlarged hairs absent from pronotum (but thin erect hairs present) (Figs 2, 3, 17, 18) 4
- Enlarged hairs present on pronotum (Figs 14, 15, 19, 20)............................................6
4. Enlarged hairs on gaster limited to a small central cluster (Figs 2, 3)........... aureopilus
- Enlarged hairs on gaster covering entire dorsal surface (or nearly so) (Figs 17, 18)... 5
5. Erect hairs on dorsum of mesosoma abundant (Fig. 18); dorsal surface of head reticulo-punctate and with a matte appearance; enlarged hairs on gaster more extensive (Fig. 17)....................................................................................................... posteropilus
- Erect hairs on dorsum of mesosoma fewer (Fig. 29); dorsal surface of head with very fine leather-like sculpturing and relatively shiny; enlarged hairs on gaster less numerous(Fig. 28) ................................................................................................. xanthopilus
6. Enlarged hairs on pronotum covering the entire dorsal surface (Figs 14, 15) .............. 7
- Enlarged hairs on pronotum limited to a band along the central 1/3 of its width (Fig. 20) ....................................................................................................................................... 8
7. Enlarged pronotal hairs white (Figs 14, 15); pubescence on dorsum of head abundant and closely spaced (Fig. 13)............................................................................ mussolinii
- Enlarged pronotal hairs pale (but distinctly) yellow (Figs 8, 9); pubescence on dorsum of head thin and widely spaced (Fig. 7) ......................................................... densopilus
8. Dorsal surface of head with abundant, closely spaced pubescence; mesonotum strongly arched and dorsum of mesosoma forming a strong arch with the propodeum relatively low (similar to Fig. 6); dorsum of gaster golden yellow, lighter in color than mesosoma ...................................................................................................... flavocrines
Camponotus (Myrmogonia) aureopilus Viehmeyer 1914: 531. Worker syntypes from Rawlinson Mountains , Papua New Guinea (not examined).
Camponotus (Myrmophyma) aureopilus var. velutina Stitz 1938: 120. Two worker syntypes from north-eastern Papua New Guinea (specific locality unknown) (not examined). New synonym.
Diagnosis (minor worker). Enlarged hairs absent from pronotum (but thin erect hairs present); enlarged hairs on gaster limited to a small central cluster.
Description (minor worker). Posterolateral margin of head angular, the dorsal surface weakly convex, the lateral surface weakly concave, a ridge running from just below the eye to the posterolateral corner. Petiolar node tapering dorsally into a blunt angle. Individual erect hairs scattered on dorsum of mesosoma, petiole and gaster; enlarged yellow hairs present on central region of the gastral dorsum; pubescence abundant on entire body. Colour black, gaster dark red-black, legs dark red.
Measurements. Minor worker (n=2): CI 92-94, HL 1.80-2.21mm, HW 1.65- 2.08mm, ML 2.78-3.19mm, MTL 2.06-2.25mm, SI 120-139, SL 2.29-2.50mm.
Material Examined. Papua New Guinea : Mt. Lina, Cyclops Mountains, 3,500ft. ( Cheesman,L.E. ) ( LACM ).
Comments. Emery (1925) transferred this species from the subgenus Myrmogonia (where it was originally placed) to Myrmophyma , with Santschi (1928) subsequently transferring it to Thlipsepinotus . Unfortunately the subgeneric classification within Camponotus is currently rather confused and subgeneric placements are difficult to assess rigorously. The queen was described by Stitz (1938), but little else is known about this species.
Stitz (1938) described velutinus as a subspecies of aureopilus , citing differences in the shape of the petiolar node to justify his new taxon. However, even with the limited material currently available this difference is slight and there appears to be little justification for recognising this taxon as distinct from aureopilus . Because of this velutinus is here treated as a synonym of aureopilus .
