Brachyponera chinensis

Buczkowski (2016) - The Asian needle ant, Brachyponera chinensis, is an invasive ant species introduced into the United States from Japan in the early 1930s (Smith 1934). Following the initial introduction, the species remained largely inconspicuous for several decades (McGown 2009). Recently, however, P. chinensis have become widespread in parts of the southeastern US and are now a common pest in urban and natural habitats (Guenard and Dunn 2010). In mature temperate forests, P. chinensis cause a strong decline in native ant abundance (Guenard and Dunn 2010) and disrupt ant-seed dispersal mutualisms by displacing native keystone ant species (Rodriguez-Cabal et al. 2012). In parts of North Carolina, USA, P. chinensis are displacing Linepithema humile by expanding their colonies early in the season (Spicer-Rice and Silverman 2013). Furthermore, recent predictive modeling demonstrates that climate change is going to significantly increase the global spread of P. chinensis by increasing the amount of habitat suitable to their invasion by 65 % worldwide (Bertelsmeier et al. 2013). The biology of P. chinensis is unique among invasive ants. First, while most invasive ants utilize carbohydrate-rich food sources consisting of floral nectar and hemipteran honeydew (Holway et al. 2002), P. chinensis is a predatory ant and a termite specialist (Bednar and Silverman 2011). There is no evidence that P. chinensis consumes nectar or hemipteran honeydew. Second, most invasive ants use mass recruitment via trail pheromones to collect food or toxic baits during management attempts. In contrast, no trail pheromones have been detected in P. chinensis. Instead, P. chinensis employs a unique yet relatively slow recruitment process called tandem carrying whereby foraging workers carry nestmates from the nest to the food source which is subsequently retrieved (Guenard and Silverman 2011). Finally, unlike colonies of many invasive ants which dominate urbanized and disturbed habitats, colonies of P. chinensis have the unique ability to invade habitats in undisturbed hardwood forests.

Identification
Mackay and Mackay (2010): Brachyponera chinensis is an Old World species that was introduced into the New World. The combination of poorly developed mandibular teeth, the constriction at the metanotal suture and the form of the subpetiolar process, with a posteriorly directed lobe separate this species from all of the others present in the New World. Only the introduction of additional Old World species (at least in the New World) would make recognition of this species difficult.

Also see Brachyponera nakasujii for details about closely related species and the Caste section below for images that can help with determinations.

Distribution based on Regional Taxon Lists
Australasian Region: New Zealand. Indo-Australian Region: Philippines. Nearctic Region: United States. Oriental Region: Cambodia, Laos, Taiwan, Thailand, Vietnam. Palaearctic Region: China, Democratic Peoples Republic of Korea, Japan, Republic of Korea, Russian Federation.

Japan (Honshu, Shikoku, Kyushu, Nansei Is, Ogasawara Is).

Habitat
From Mackay and Mackay (2010):Smith (1979) reports they occur in dark damp habitats in urban environments (Smith, 1934) and disturbed rural environments (Brown, 1958).

Biology
As this ant is found in more areas, and is becoming known as a destructive invasive pest, it is becoming an increasingly focused on species of interest. A climate change analysis (Bertelsmeier et al. 2013) predicts global warming will greatly increase the potential areas where Brachyponera chinensis can invade. Its northern spread in eastern North America will perhaps not be as dramatic as predicted by climate alone. Its preferred prey, termites, are lacking in most of the putative areas of possible range expansion.

Mackay and Mackay (2010): Smith (1934), Koriba (1963) and Gotoh and Ito (2008) summarized the biology of this species. Small colonies were found in moist rotten wood or in the soil under stones, logs, debris, etc. (Smith, 1934). Sexuals were found in a nest in August in Norfolk, Virginia. Foragers were more active on cloudy days as compared with sunny days. They fed on dead insects, fish scraps and juices of decayed fruits lying on the ground. People at one unspecified locality claimed that they were occasionally stung. At the time of collection (spring, 1932) they were most common in the vicinity of the docks. They occurred over the entire town of Washington, North Carolina and to a lesser extent of Norfolk, Virginia. These ants are unusually common and successful in China and apparently feed on dead insects (Brown, 1958).

Eyer et al. (2018) found that a bottleneck at the population scale has not affected the diversity or the level of heterozygosity within colonies, as inbreeding is not a consequence of the founder event, but is due to mating between sibs that pre-existed in native populations. This suggests generations of sibmating in native populations might have pre-adapted B. chinensis as a successful invader, reducing inbreeding depression through purifying selection of deleterious alleles.

Foraging/Diet
Bednar and Silverman (2011) studied the association of this ant with termites in North Carolina: Pachycondyla chinensis nests in close proximity to and consumes subterranean termites (Rhinotermitidae). P. chinensis do not occur in habitats lacking Rhinotermitidae. We suggest that subterranean termites are critical for P. chinensis success in new habitats. We demonstrate that P. chinensis is a general termite feeder, retrieving Reticulitermes virginicus five times more often than other potential prey near P. chinensis colonies. Odors produced by R. virginicus workers, as well as other potential prey, attract P. chinensis. Furthermore, P. chinensis occupy R. virginicus nests in the lab and field and display behaviors that facilitate capture of R. virginicus workers and soldiers. Termites are an abundant, high quality, renewable food supply, in many ways similar to the hemipteran honeydew exploited by most other invasive ant species. We conclude that the behavior of P. chinensis in the presence of termites increases their competitive abilities in natural areas where they have been introduced.

Buczkowski (2016) - Behavioral observations revealed that P. chinensis become visibly excited when a termite was present within approximately 2 cm away. The ants exhibited fast, erratic running and directed movement toward the termite. This suggests that termites emit volatile chemicals that are detected by P. chinensis that may help the ants locate their prey. Alternatively, P. chinensis may use visual cues in locating termites or a combination of visual and chemical cues.

Guénard and Silverman (2011) - Tandem carrying was previously described in Japanese by Takimoto (1988), however none of the reviews or studies on foraging recruitment published later considered this study (Beckers et al. 1989; Traniello 1989; Hölldobler and Wilson 1990; Baroni Urbani 1993; Passera and Aron 2006). In Brachyponera chinensis in North Carolina tandem carrying was first observed in June 2007. We later tested for the occurrence of this behavior near other B. chinensis colonies in four separate locations in Cary and Raleigh, NC by providing cockroaches, adult B. germanica L, to elicit recruitment. In all cases, tandem carrying was observed in response to food placement. This same behavior was also later observed in the native range of B. chinensis in Okayama, Japan. A successful tandem carry by B. chinensis comprises several steps. A scout returns to the nest following the discovery of food too large to be moved by a single individual. Upon return to the nest, the scout solicits a nestmate worker by drumming it with its antennae. The antennated worker assumes a pharate (pupal)-like posture with legs appressed to the thorax. The scout, now referred to as the carrier, then picks it up. The carrier holds the recruited worker within its mandibles between the worker’s first and second pairs of legs of the mesometasternum. The carried worker’s head is positioned upwards while being transported to the food, after which it is released directly adjacent to or nearly within a 2-cm radius of the food. Interestingly, the path taken by the tandem pair to the food is not linear but instead typically convoluted. Out of 28 observations, the carrier worker returned to the nest in 26 cases (93%) after the release of the carried worker but remained at the food in two cases. In most cases, carrier workers were observed turning around and inspecting the food prior to returning to the nest but without carrying any food themselves. We observed the dissection of large prey into smaller pieces, which were then transported to the nest by individual workers.

While tandem carrying appears ubiquitous within B. chinensis, expression of this behavior is context dependent. This is evidenced by the fact that tandem carrying occurred three to ten times more often with large nonmovable vs. small removable prey during peak foraging. We found no evidence for pheromone involvement in B. chinensis tandem-carrying recruitment. The mechanism by which the scout is able to return to the food and the mechanismby which the carried worker finds the nest are unresolved, although visual orientation cues may be employed (e.g., Jaffe et al. 1990; Collett and Collett 2002).

We consider tandem carrying as documented here in B. chinensis to be an original recruitment foraging strategy, perhaps the simplest yet described. In B. chinensis, the expression of this behavior is characterized by a graded recruitment and by high spatial and temporal flexibility. First, the number of tandem carrying events is resource dependent, with more recruitment to large prey that cannot be carried by a single worker than smaller movable prey, even at high density. Second, the recruitment observed by tandem carrying can be adjusted quickly in space and within a time period of 5 to 10 min to maximize the exploitation of larger prey. The low recruitment efficiency of this behavior seems to be balanced by a strong flexibility.

Colony Attributes
Gotoh and Ito (2008) studied a population in its native range: Mt. Yoshio-yama, Takamatsu-shi, Kagawa Prefecture, Shikoku Isl., western Japan. The abstract from their study: We investigated the seasonal cycle of changes in the colony structure of B. chinensis reproduced by alate queens in western Japan, and found the following novel biological characteristics of this species. B. chinensis showed a remarkable caste dimorphism in ovariole numbers: workers had no ovaries while queens had 18 to 36 ovarioles in their ovaries. The nesting system seemed to be polydomous: 266 of 400 nests collected were queenless. The number of queenless nests increased during the reproductive season. Among the 134 queenright nests, 38 had several mated-queens without significant differences in ovary activation and the remaining 96 nests were monogynous. During winter to early spring, most nests were polygynous. After alate production, most of the old queens seemed to die or be expelled and replaced by new queens. Virgin dealated queens were often found and they seemed to have laid eggs.

Allen et al. (2017) studied nesting relocation in a laboratory setting: "Subsets of B. chinensis worker ants were subjected to physical nest disturbance, and the recruitment methods and associated behaviors were recorded. Before recruitment to the new nest location began, B. chinensis ants organized into three distinctive groups: queen-tending, broodtending, and scouting. Once the new nest site was identified, scout ants began physically transporting nestmates into the new harborage. Transport rates increased with time in the first 30 minutes and did not change during the 30 to 55 minute interval when brood was transported. However, adult transport rate increased again after brood transport was completed and decreased after 90 minutes."

Ant Community Interactions
Guénard and Dunn (2010): Examined ant diversity and abundance in mature forests of North Carolina. Where it was present, P. chinensis was more abundant than all native species combined. The diversity and abundance of native ants in general and many individual species were negatively associated with the presence and abundance of P. chinensis. A small subset of species larger than P. chinensis (Camponotus and Formica) was either as abundant or even more abundant in invaded than in uninvaded sites. The large geographic range of this ant species combined with its apparent impact on native species make it likely to have cascading consequences on eastern forests in years to come.

Rodriguez-Cabal et al. (2012) in North Carolina, USA found B. chinensis was negatively correlated with the presence of Aphaenogaster rudis, decreased the seed removal rate of a myremchorous plant seed and was negatively correlated with a second forest plant that produces mymecochorous seeds: "The number of A. rudis workers was 96% lower in invaded than in intact plots, and the number of seeds removed was 70% lower in these plots. Finally, in invaded plots the abundance of Hexastylis arifolia, a locally abundant myrmecochorous plant, was 50% lower than in plots where P. chinensis was absent. A parsimonious interpretation of our results is that P. chinensis causes precipitous declines in the abundance of A. rudis within invaded communities, thereby disrupting the ant-plant seed dispersal mutualisms and reducing abundances of ant-dispersed plants.

Spicer Rice and Silverman (2013) found P. chinensis is displacing another invasive ant, Linepithema humile, in an urban habitat in Morriseville, North Carolina. The latter is at the northern limits of its range while the former, more adapted to cooler winters, is not at an edge of its invaded range. P. chinensis was found to be active up to two months before L. humile. Their findings suggests the lower thermal tolerance of the ponerine helps in establishing itself before L. humile begins their spring activity and this provides an important competitive advantage.

Warren et al. (2015) - In the deciduous forests of the north Georgia Piedmont the increasing abundance of B. chinensis is displacing the native Aphaenogaster rudis. B. chinensis was diminishing the abundance of A. rudis. Like the latter it was also preying upon, perhaps more effectively than A. rudis, on the termite Reticulitermes flavipes. In contrast to A. rudis B. chinensis was not serving as an effective seed disperser of myrmecochorous seeds in this forest habitat.

Nomenclature

 * solitaria. Ponera solitaria Smith, F. 1874: 404 (w.) JAPAN. [Junior primary homonym of solitaria Smith, above.] Forel, 1900e: 267 (q.). Combination in Euponera (Brachyponera): Emery, 1901a: 47. Senior synonym of chinensis and hence the latter the first available replacement name: Brown, 1958h: 22.
 *  chinensis. Ponera nigrita subsp. chinensis Emery, 1895k: 460 (w.) CHINA. [Misspelled as sinensis by Imai & Kubota, 1972: 194.] Replacement name for solitaria Smith, F. 1874: 404. [Junior primary homonym of solitaria Smith, F. 1860b: 103.] [Note: chinensis junior synonym of solitaria Smith, F. 1874: 404 (synonymy by Brown, 1958h: 22); hence first available replacement name.] Wheeler, W.M. 1921c: 530 (q.); Ogata, 1987: 116 (m.); Wheeler, G.C. & Wheeler, J. 1986c: 88 (l.); Imai & Kubota, 1972: 194 (k.). Combination in Euponera (Brachyponera): Emery, 1909c: 367; in Brachyponera: Brown, 1958h: 22; in Pachycondyla: Brown, in Bolton, 1995b: 304; in Brachyponera: Schmidt & Shattuck, 2014: 80. Raised to species: Brown, 1958h: 22. See also: Mackay & Mackay, 2010: 247.

Type Material
Ponera solitaria

Two worker syntypes in. Labelled “Japan. 74/16.” Acc. Reg.: “1874 no. 16. 2 Ponera solitaria. Hiogo (Japan). Presented by Fred. Smith. These insects were all collected by Mr Geo. Lewis, except those from Hokadadi which were collected by Mr Whiteley and Mr R. Fortune.” In the original description Smith gives the type-locality merely as “Hiogo.”

Worker
Mackay and Mackay (2010): The worker is a small (total length 3.5 mm) brown specimen with yellowish brown mandibles, funiculi and legs. The mandibles have approximately 9 teeth, which alternate in size. The three apicalmost teeth are the largest with the first tooth approximately twice the length of the other two, which are approximately the same size. The transverse medial carina is poorly marked on the clypeus, the sides of the head are nearly parallel and the posterior margin is slightly concave. The head length is 0.88 mm; the head width is 0.75 mm. The eye is relatively large (maximum diameter 0.15 mm), located less than one diameter from the anterior margin of the head. The scape (0.85 mm) extends approximately two funicular segments past the posterior lateral corner of the head. The funicular segments are slightly swollen toward the apex, but do not form a club. The mesonotum is well defined on all sides and the mesosoma notably depressed at the metanotal suture. The propodeal spiracle is circular. The petiole is narrow when viewed in profile, with the anterior face being slightly concave near the apex and posterior face being slightly convex. Both faces narrow towards the apex and form a small horizontal dorsal surface. The subpetiolar process is a broad thick lobe, with a posteriorly directed sharp process. The metasternal process consists of two fang-like sharp elongate projections, similar to those found in members of the stigma species complex.

Erect hairs are sparse, but are present on the mandibles, clypeus, frontal lobes, a few hairs are present on the dorsum of the mesosoma, dorsum of the petiole and all surfaces of the gaster, a few hairs on the legs are erect. Very fine appressed sparse golden pubescence is found on most surfaces.

The mandibles are finely striated with scattered punctures the dorsum of the head is very finely and densely punctate and weakly shining, the dorsum of the mesosoma has similar sculpture. The sculpture on much of the side of the mesosoma, especially the side of the pronotum and mesopleuron and the lower part of the propodeum is smooth and glossy. The petiole has scattered punctures and is weakly shining; the gaster is sculptured and is slightly shinier.

Etymology
The name means that this species is from China. (Mackay and Mackay 2010)