Calyptomyrmex beccarii

This is by far the most widespread species in the genus, occurring from Singapore north-east to the Philippines and south to Papua New Guinea and northern Australia. As with most other species within this genus, beccarii is found in rainforest and is most often encountered in leaf litter samples, although one nest was found in a carton termite nest.

Identification
Hairs on head and body spatulate (noticeably narrower near the body and expanded distally and with a rounded tip) and appressed closely to the underlying body surface, gaster finely and indistinctly sculptured, propodeum unarmed, posterior margin of head more rounded, especially its lateral corners. This species is most similar to Calyptomyrmex loweryi but differs in having the head narrower above the level of the antennal scrobe and in being smaller (head width < 1.10mm rather than greater than 1.13mm).

Distribution based on Regional Taxon Lists
Australasian Region: Australia. Indo-Australian Region: Borneo, New Guinea, Philippines, Singapore. Oriental Region: Thailand.

Nomenclature

 *  beccarii. Calyptomyrmex beccarii Emery, 1887b: 472, pl. 2, fig. 23 (w.) NEW GUINEA. Szabó, 1910a: 365 (q.). Senior synonym of rufobrunnea: Brown, 1951: 101; of schraderi: Taylor, 1991b: 600; of emeryi, glabratus: Shattuck, 2011: 5.
 * emeryi. Calyptomyrmex emeryi Forel, 1901h: 51 (w.m.) BORNEO. Wheeler, W.M. 1919e: 90 (q.). Junior synonym of beccarii: Shattuck, 2011: 5.
 * schraderi. Calyptomyrmex schraderi Forel, 1901h: 50 (q.m.) AUSTRALIA. Junior synonym of beccarii: Taylor, 1991b: 600.
 * glabratus. Calyptomyrmex beccarii var. glabratus Viehmeyer, 1916a: 128 (w.) SINGAPORE. Raised to species: Baroni Urbani, 1975a: 410 (in key). Junior synonym of beccarii: Shattuck, 2011: 5.
 * rufobrunnea. Weberidris rufobrunnea Donisthorpe, 1949a: 281, fig. 1 (w.) NEW GUINEA. Combination in Calyptomyrmex: Donisthorpe, 1949f: 186; Brown, 1949f: 84. Junior synonym of beccarii: Brown, 1951: 101.

Worker (apparently a single specimen, therefore holotype) from Ambon (as Amboina), Indonesia.

Although this species is not particularly morphologically variable, it has been described no fewer than five times. For example, Taylor (1991) recognised that schraderi was conspecific with beccarii and also speculated that glabrata might be a junior synomym as well, although he did not study this last problem in detail and left the taxonomic status of these taxa unchanged. These proposals, as well as the synonymy of emeryi, were supported by Shattuck (2011).

Taylor’s (1991) synonymy of the Australian-based schraderi with beccarii was confirmed by Shattuck (2011). However, it should be noted that the Australian populations do show slight differences when compared to more northern populations. Specifically, the spatulate hairs on the head and mesosoma of northern populations are narrower and more slender compared to the broader and more rounded hairs found in Australian specimens. However, hairs on the gaster are essentially identical and no further differences were found. Thus the available evidence suggests that these differences are little more than population-based geographic variation.

Comparable differences are also present in the single specimen of this taxon from East Timor. While very similar to other specimens examined during this study, this specimen differs in having the spatulate hairs on the head and mesosoma more erect and raised distinctly above the surface of the body. In specimens from other regions these hairs are at most only slightly raised above the surface. As with Australian specimens, no other differences were detected and this specimen was considered by Shattuck (2011) to belong to beccarii.

The types of glabratus, the western-most samples known for this species, show only slight differences from other specimens placed in this taxon by Shattuck (2011). These differences include the petiolar node in lateral view being slightly higher and more angular and the pronotal corners in dorsal view being more angular compared to specimens from further east. However, these differences are slight and are not unexpected for such a wide-spread species. Because no additional differences could be found glabratus is considered to be a junior synonym of beccarii. This confirmed the suspicions of Taylor (1991).

Finally, an examination of the holotype of emeryi shows this taxon conforms to the concept of beccarii developed by Shattuck (2011) and is a straightforward synonym. Forel (1901) provided a very brief description and failed to note any differences between this species and either beccarii or schraderi (which he described in the same paper as emeryi). None could be found by Shattuck (2011) and therefore this name is treated as conspecific with beccarii.

Description
'''Worker description. '''Mandibles delicately striate (sometimes weakly so). Eyes with 5–6 ommatidia in greatest diameter. Propodeum in lateral view lacking angles or spines. Propodeal lobes thin anteriorly, thickened posteriorly. Node of petiole in profile slightly higher and larger than that of postpetiole. In dorsal view the petiolar node slightly narrower than the postpetiolar node. Head, promesonotum, dorsal and posterior faces of propodeum and petiolar and postpetiolar nodes rugose, the rugae enclosing foveolate spaces, this sculpturing most strongly developed on the front of the head, weaker and less defined posteriorly. Sides of mesosoma irregularly rugose, more strongly on pronotum, weakly so on propodeum. Spaces between rugulae indistinctly shagreened or finely reticulate-punctulate, matt and dull. Gaster finely and indistinctly sculptured. Hairs on head and body spatulate and appressed. Clypeal fork with spatulate hairs only. Colour dull red-brown.

Measurements. Worker (n = 11) - CFW 0.19–0.22; CI 97–105; HL 0.95–1.06; HW 0.93–1.09; ML 0.9 1–1 .02; MTL 0.43–0.53; PetI 123–148; PetL 0.22–0.28; PetW 0.29–0.39; PronW 0.60–0.74; SI 50–54; SL 0.49–0.57.

Additional References

 * Baroni Urbani, C. (1975) Primi reperti del genere Calyptomyrmex Emery nel subcontinente Indiano. Entomologica Basiliensia, 1, 395–411.
 * Brown, W.L., Jr. (1949) Revision of the ant tribe Dacetini. 4. Some genera properly excluded from the Dacetini, with the establishment of the Basicerotini, new tribe. Transactions of the American Entomological Society, 75, 83–96.
 * Brown, W.L., Jr. (1951) New synonymy of a few genera and species of ants. Bulletin of the Brooklyn Entomological Society, 46, 101–106.
 * Donisthorpe, H. (1949a) A new genus and species of dacetine ant from New Guinea. Entomologist's Monthly Magazine, 84 (1948), 281.
 * Donisthorpe, H. (1949b) A species of Calyptomyrmex Emery from New Guinea. Entomologist's Monthly Magazine, 85, 186.
 * Emery, C. (1887) Catalogo delle formiche esistenti nelle collezioni del Museo Civico di Genova. Parte terza. Formiche della regione Indo-Malese e dell'Australia (continuazione e fine). Annali del Museo Civico di Storia Naturale di Genova, (2) 5[25], 427–473.
 * Forel, A. (1901) Formiciden des Naturhistorischen Museums zu Hamburg. Neue Calyptomyrmex, Dacryon, Podomyrma, und Echinopla-Arten. Jahrbuch der Hamburgischen Wissenschaftlichen Anstalten, 18, 45–82.
 * Taylor, R.W. (1991) Nomenclature and distribution of some Australasian ants of the Myrmicinae. Memoirs of the Queensland Museum, 30, 599–614.
 * Szabó, J. (1910) Formicides nouveaux ou peu connus des collections du Musée National Hongrois. Annales Historico-Naturales Musei Nationalis Hungarici, 8, 364-369.
 * Shattuck, S.O. (2011) Revision of the ant genus Calyptomyrmex (Hymenoptera: Formicidae) in South-east Asia and Oceania. Zootaxa, 2743, 1-26.
 * Viehmeyer, H. (1916) Ameisen von Singapore. Beobachtet und gesammelt von H. Overbeck. Archiv für Naturgeschichte, 81 (A.8) (1915), 108-168.
 * Wheeler, W.M. (1919) The ants of Borneo. Bulletin of the Museum of Comparative Zoology, 63, 43–147.