Bannapone

This rarely encountered genus is known from only a handful of collections from China. Queens of one species have been collected from a soil sample in semi-evergreen monsoon forest and a leaf litter sample in a tropical rainforest. The two worker specimens, of the second known species, were collected from a single site located at 550 meters elevation, consisting of secondary forest habitat with thick leaf litter cover and abundant decomposing woody material on the forest floor. These workers were collected from leaf litter using Winkler extraction.

Identification
Zu (2000) - Bannapone is distinctly a genus of the tribe Amblyoponini of the subfamily Ponerinae based on the articulation way of the petiole and the first gastral segment although known only from the dealate female caste. The 11-segmented antennae, the special mandible and the extremely small body size indicate the genus displays an isolate evolutionary way in the tribe. According to the features of the mandibles, the new genus is close to Prionopelta, but the 2 genera can be distinguished by the characters of mandibles, clypeus, antennae, and gaster. The new genus becomes the fifth living genera of the tribe Amblyoponini in Oriental and Indo-Australian Regions.

Guénard, Blanchard, Liu, Yang, and Economo (2013) - The genus Bannapone is distinguished from all other Amblyoponinae genera by the strongly falcate, 3-toothed mandibles. In particular, Bannapone is easily distinguished by the mandibular shape composed of three distinct and long teeth (especially the apical tooth) versus the triangular shape of Concoctio. The genus Prionopelta also has three mandibular teeth, but the mandible is subtriangular, with the teeth clustered near the apex (Xu 2000). Furthermore, the mandible length relative to the head is much larger in Bannapone than in Prionopelta or Concoctio. The mandible length is over 85% of head length in Bannapone scrobiceps, and over 79% in Bannapone mulanae. In contrast, mandibles are proportionately much shorter in Prionopelta and Concoctio. It should also be noted that the eyes are absent in the worker caste of B. scrobiceps, but present, while sometimes reduced in Concoctio and Prionopelta. The 11-segmented antennae are confirmed within B. scrobiceps, which is distinct from the 9- segmented antennae of Concoctio, but variation occurs within other Amblyoponinae genera such as Prionopelta, in which antennal segments vary from 8 to 12 (Xu 2000), and this morphological trait could be more labile in Bannapone as well. Xu (2000) also differentiates Bannapone from Prionopelta based on abdominal segments III and IV being as large as the other segments, occupying less than half of the length of the gaster, and with indistinct constriction between them. The discovery of B. scrobiceps confirms this. The length of abdominal segments III and IV combined represent less than half of the total length of the gaster. However, it should be noted that the visibility of the abdominal segments V and VI can vary substantially due to the preservation of the specimen examined. As a consequence, this character should be considered cautiously. Finally, the constriction between abdominal segments III and IV in B. scrobiceps, while slightly more apparent than in B. mulanae, is still less constricted than observed in Prionopelta species.

Other morphological differences between Bannapone and Prionopelta discussed by Xu (2000) need to be modified or complemented after the discovery of B. scrobiceps. A distinction between Bannapone and Prionopelta noted by Xu (2000) is the “very narrow” clypeus in Bannapone. In B. scrobiceps the clypeal area is more developed than in B. mulanae, and its size seems comparable to certain Prionopelta species such as P. descarpentriesi Santschi from Madagascar. As a result clypeus size should not be retained as a characteristic to separate these two genera. Xu (2000) also reports the frontal lobes as “closely approximated”, however in B. scrobiceps, the frontal lobes are widely separated and thus this morphological criterion should not be retained. The antennae were also described with the presence of a “gradually incrassate strong club” (Xu 2000). However, in B. scrobiceps, the antennae are incrassate but do not form a strong club and as such the presence of an antennal club is not characteristic of the genus. Contrary to the original description of Bannapone (Xu 2000), we observed well-developed metapleural lobes. Finally, the subpetiolar process of B. scrobiceps is more developed than in B. mulanae and as a consequence this trait no longer differentiates Bannapone and Prionopelta. Finally, Xu (2000) characterized the genus Bannapone as extremely small. The worker of B. scrobiceps is larger than the queen of B. mulanae (3.3mm vs. 2.1mm). The new specimens confirm the relatively small size of the genus within Formicidae, but relative to several other genera found in the same area (e.g. Carebara, Leptanilla, Prionopelta), Bannapone should not be characterized as extremely small. Furthermore, it seems possible that more variation could exist. For example, the queen caste of B. scrobiceps, still unknown, is probably larger than the worker caste, as is typical for many ant species (but see exceptions in Molet et al. 2007, Kikuchi et al. 2008).

To summarize, diagnosis of Bannapone should be based on the peculiar shape of the mandibles formed of three teeth on the masticatory margin with the apical tooth very long and followed by 2 blunt finger-like basal teeth. Bannapone is also distinct from Prionopelta by the high ratio of the mandible length relative to head length (> 0.75), the indistinct constriction between the abdominal segments III and IV, and with the limitations presented above, by the presence of the abdominal segments III and IV as large as the other segments, which combined length represents less than half of the total length of the gaster.

Distribution
Known only from Yunnan Province, China.

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Castes
Males have not been collected.

Nomenclature

 *  BANNAPONE [Amblyoponinae]
 * Bannapone Xu, 2000b: 299. Type-species: Bannapone mulanae, by original designation.

Queen
Dealate female: Body small. Head relatively depressed. Mandibles narrow, long triangular, inner margin shorter than masticatory margin. Masticatory margin with 3 teeth, the apical tooth very long and bifid at most apex, followed by 2 blunt finger-like basal teeth. Clypeus narrow and transverse. Frontal lobes horizontal, closely approximated and partially covered the antennal sockets. Eyes of moderate size, at the midlength of the sides of the head. Ocelli present. Antennae 11-segmented, with a gradually incrassate strong club. Alitrunk with full complement of flight sclerites and certainly winged when virgin, dorsum evenly arched in profile view. Propodeum unarmed, declivity depressed vertically, propodeal spiracles small, about in the middle of the sclerite.Metapleural gland bulla small and horizontal. Metapleural lobes absent. Middle legs without tibial spurs, basitarsus curved; hind legs with only a pectinate spur. Petiole roughly rectangular, broadly attached to first gastral segment, subpetiolar process narrow and cuneiform. Gaster large and elongate, with similar segments, constriction between the 2 basal segments indistinct. Sting strong and functional. Hairs sparse, pubescences abundant.