ASIAN MYRMECOLOGY Volume 10, e010012, 2018ISSN 1985-1944 | eISSN: 2462-2362 © Benoit Guénard

DOI: 10.20362/am.010012

First record of the emerging global pest Brachymyrmex patagonicus
Mayr 1868 (Hymenoptera: Formicidae) from continental Asia
Benoit Guénard
School of Biological Sciences, The University of Hong Kong,
Hong Kong SAR
Corresponding author: zeroben@gmail.com*

ABSTRACT. The first record of the exotic ant Brachymyrmex patagonicus
Mayr 1868 from continental Asia is here presented. Specimens collected froman urban environment in Hong Kong coupled with recent surveys suggest an
early stage in the invasion process. The summary of recent records shows thatthe introduced range of this species is quickly increasing globally and biologists
in Asia should remain vigilant to detect it. In Hong Kong, measures to identify
its overall spread and to eradicate this species, which is considered as a majorpest, should be quickly implemented.
Keywords: Brachymyrmex patagonicus, Hong Kong, Tropical Asia, Introduction, Urban Ecosystems, Tramp Ant.
The ant genus Brachymyrmex is native to the
New World and widely distributed from southern Canada to the Patagonian region of Argentina(antmaps.org, Guénard et al. 2017). The genus
diversity is relatively modest and currently includes 44 valid species, 17 valid subspecies and agood reservoir of potentially undescribed species(Deyrup 2016). However, five species have beenrecorded as introduced outside their native ranges: B. cordemoyi Forel 1895, B. heeri Forel 1874,
B. minutus Forel 1893, B. obscurior Forel 1893,
and B. patagonicus Mayr 1868. The latter species
is arguably the most widespread Brachymyrmex
species and its introduced range has quickly expanded in the past decade based on recent records
summarized below. Here the first record of B. patagonicus from continental Asia is reported from
Hong Kong.
Brachymyrmex patagonicus is native toSouth America and has been reported from thesouthern Argentinean province of Santa Cruz
north to Venezuela and the Guiana Shield, andfrom the eastern Brazilian states of Pernambuco
and Paraiba to Ecuador in the west (antmaps.org,

Guénard et al. 2017). Though the native range
has sometimes been presented as limited to Argentina or Paraguay (e.g. MacGown et al. 2007,
Hill 2017), its distribution in South America isthus more extensive, and ecological results suggest that the native range of B. patagonicus could
extend further. For instance, in a study conductedwithin the northern part of the Cerrado ecoregion (Maranhão state, Brazil), B. patagonicus
was found to be an indicator species of interior
forest, a habitat less exposed to disturbance incomparison to forest edges and agricultural fields(Brandão et al. 2011). However, it should also be
noted that within the Neotropical realm, B. patagonicus is frequently encountered within disturbed open habitats or anthropogenic habitats(Delabie et al. 2009, Santos-Silva et al. 2016,
Golias et al. 2018) suggesting that some populations could represent more recent introductions.
Determining the exact native range of this species
within South America is thus needed at this point.
Within the United States, where the species is non-native, MacGown and collaborators
reported B. patagonicus from seven states in 2007

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Benoit Guénard

(Florida, Georgia, Alabama, Mississippi, Louisiana, Arkansas and Texas) but in just 12 years, additional records from California (Martinez et al.
2011), North Carolina (Guénard et al. 2012), Arizona (MacGown et al. 2013), New Mexico (MacGown et al. 2013), South Carolina (MacGown etal. 2013), Missouri (Trager 2014), Nevada andTennessee (Hill 2017) have been reported, with
B. patagonicus now widespread within the southern American states from coast to coast across 15
states. In the Caribbean region, B. patagonicus is
known from the Bahamas (Wheeler & Wheeler1978) and was recently reported from Martinique(Carval et al. 2016).
In the Old World, B. patagonicus has
been reported in Europe from greenhouses of
the Kew Gardens, London (England) since 1909
and more recently in the early 2000’s from greenhouses and zoos in the Netherlands (Vierbergen
2003, Boer & Vierbergen 2008). However, forboth countries, it is uncertain if these populations
persist (e.g. see Brangham 1938) and no outdoor
populations have been reported. The situation differs in Spain, where B. patagonicus was recently
reported from the coastal city of Almería (Almería
province) where it was collected both indoors andoutdoors (Espadaler & Pradera 2016). In Asia, asingle record of B. patagonicus has been reported
from the harbor area of Kobe, Hyogo prefecture,
Japan (Terayama et al. 2014), however further investigation to determine if this population remains
and has been able to survive the cooler climate of
the region would be welcome.
Because of its small size and the lack ofa recent and comprehensive taxonomy, the genus
Brachymyrmex has caused much confusion historically among ant biologists (MacGown et al.
2007, Deyrup 2016). For instance, early recordsof the Mesoamerican species B. musculus Forel
1899 from the USA and the Bahamas (Wheeler &Wheeler 1978) were misidentifications of B. patagonicus in (MacGown et al. 2007). Similarly,
early records of B. brevicornis from Florida (Deyrup et al. 2000) represent an undescribed speciesof Brachymyrmex (MacGown et al. 2007), or therecord of B. aphidicola Forel 1909 from Hawaii(Wheeler 1934) represents a misidentification of
B. obscurior (Huddleston & Fluker 1968). Recent
taxonomic work initiated by Quirán and collaborators (2004) and later completed by MacGownand collaborators (2007) defined B. patagonicus from the following morphological characters (briefly summarized here): brownish-yellow
scapes exceeding the occipital margin of head by

Figure 1: Pictures of a specimen of B. patagonicus collected from Hong Kong showing A) a head, B) a profile
and C) a dorsal view.

First record of the emerging global pest Brachymyrmex patagonicus Mayr 1868
(Hymenoptera: Formicidae) from continental Asia

1/5 of their total length, eyes well-developed andas large as the malar space, decumbent pubescence on head and gaster sparse with the presenceof a few long and scattered erect hairs, promesonotum with a few erect hairs (3 to 9) on dorsum
when specimens observed in profile view. Thesemorphological characters are clearly observed on
the specimens collected in Hong Kong (Figure 1)
from Kowloon, Hung Hom district, waterfront,
22.302074N, 114.191298E, 4 m elev., 11 & 16
December 2018, B. Guénard col.
The collecting site in Hong Kong is located at the tip of a zone of reclaimed land andheavily urbanized. The specimens were first observed foraging at the base of two planted Araucaria heterophylla (Salisb.), an introduced tree
species within a landscaped urban habitat. Foraging activities were observed on December 11th in
the morning at 8:45am and around 10:30am. At
the time of the initial observation, atmospherictemperature was close to 17°C, and while the bark3

surface was directly exposed to the sun, constantwind likely cooled the surface. On the afternoon
of December 16th (3 to 4:30pm), additional sampling was performed using baits (cookie crumbs)
to collect more workers and other species in thevicinity. Over 60 workers of B. patagonicus wereobserved, including a few meters away from theoriginal sites (within a radius of 5m) on bareground and lawn (Figure 2). A few individuals were observed at collecting baits, however
no mass-recruitment was observed despite thehigh ground temperature measured (22.7°C to25.8°C). While workers were observed using asimilar trail suggesting the potential use of pheromonal communication, the density of workers
observed was low. Three other ant species wereobserved in the same area, Pheidole megacephala (Fabricius, 1793) which appeared dominant on
baits, and more rarely Paraparatrechina sauteri(Forel, 1913) and Cardiocondyla minutior Forel,
1899; the latter is here recorded for the first time

Figure 2: Landscape habitat where B. patagonicus was found in Hung Hom, Hong Kong. White arrows indicate
areas where the species was found foraging.

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Benoit Guénard

in Hong Kong as well and was recently collected from the nearby territory of Macao (Leonget al. 2017). The presence of B. patagonicus at
the basis of a coniferous species is worth noting
as the association of this ant with pine trees has
been reported previously in its North American
introduced range (MacGown et al. 2007, Hill
2017) as well as in its native range in association with exotic pine trees in Patagonia (Corley etal. 2006). The presence of B. patagonicus withinlandscaped habitat and heavily urbanized environment (Figure 2) is similar to observations incollecting sites in other introduced regions suchas southern Spain (Espadaler & Pradera 2016), or
North Carolina, USA (North Carolina State University Campus: Guénard et al. 2014).
Risks for Hong Kong and Asia
In both its native and introduced ranges, B. patagonicus inhabits a variety of habitats along awide gradient of disturbance. The ability of thisspecies to colonize both natural habitats suchas woodlands, mangroves (Moreau et al. 2014),
grasslands (Calcaterra et al. 2016) or beaches(MacGown et al. 2007) as well as disturbed habitats such as tree plantation, agricultural fields(Delabie et al. 2009, Golias et al. 2018) or urban habitats (MacGown et al. 2007), including
indoor structures should allow B. patagonicus
to spread widely in subtropical and tropical Asia
in the absence of control measures. Though particular studies on the impacts of B. patagonicus
on native arthropods are at this point lacking, it
has been noted that this species was often foundco-occurring with other ant species (MacGown
et al. 2007). In Hong Kong its presence in thevicinity of an area invaded by P. megacephala isworth noting. Several studies also noted that B.
patagonicus was particularly attracted to carbohydrates originating from plants or hemipteraninsects (MacGown et al. 2007, Buffa et al. 2009).
In the latter case, if B. patagonicus represents anefficient guard for honeydew-producing insects,
then it might favor herbivorous insect outbreaks
or limit the efficiency of biological control programs of these insects.

Within urban settings, B. patagonicus isconsidered to be a major pest due to the nuisancethe species creates in entering buildings (MacGown et al. 2007). For instance, in separate studies conducted in hospitals, B. patagonicus has
been recorded as one of the most frequent andabundant species found in several room types including kitchens, offices, and laundry rooms, butalso more sensitive areas such as infirmaries andneonatal units (dos Santos et al. 2009, Josens etal. 2014, de Castro et al. 2016). This species alsocolonizes or forages within administrative buildings (e.g. schools) as well as households or hotels and was recognized in Mississippi as the pest
causing the most frequent interventions from pest
control companies due to its high nesting plasticity and the difficulties to control populations(MacGown et al. 2007). While the species is not
anticipated to directly damage building structures
or cause health problems, its high abundance
within buildings will nonetheless be considereda nuisance by users (MacGown et al. 2007). Its
spread across Hong Kong and Asia could thus
lead to an economic burst in pest management
costs and to an increase in the release of insecticides in the environment. Since 2014, importantefforts have been deployed in both natural and urban environments of Hong Kong to characterize
the local myrmecofauna (unpublished results) but
it should be noted that no other records of B. patagonicus have been reported to date. Moreover,a rapid inspection of nearby landscaped areas did
not uncover other workers of B. patagonicus.
This indicates that the introduction of B. patagonicus in Hong Kong might be recent, offering
an opportunity for the detection and eradicationof the species before it becomes established.
If the record of B. patagonicus in Hong
Kong represents an example of long-jump dispersal - on the basis of previous records a 2500 km
from Japan, or cross-continental dispersal from
Europe or the New World – this is not surprising. Hong Kong represents one of the major hubs
for trade in Asia and several exotic ant species
have already been recorded. For instance, Hong
Kong has been hypothesized to be entry point of
S. invicta in mainland China (although the neighboring city of Shenzhen has also been proposed;

First record of the emerging global pest Brachymyrmex patagonicus Mayr 1868
(Hymenoptera: Formicidae) from continental Asia

reviewed in Wang et al. 2013) and several newrecords of exotic or tramp species have recently
been recorded (Tang et al. in review, unpublishedresults). This confirms the continuous accumulation of exotic species across the globe and the invasion of new regions (Seebens et al. 2018), butalso the potential role that Hong Kong might play
as a stepping stone for invasion to other parts of
the world (Lu et al. 2018) generating an urgent
need for early detection and control measures tobe implemented.
ACKNOWLEDGMENTS
I would like to thank the National Geographic
Society for their invitation in Hung Hom which
provided me the opportunity to sample ants
there. I would also like to thank my wife Mariko
Yagi for her help in translating the Japanese literature. Adam Cronin and Christian Peeters arethanked for their useful comments on an earlier
version of the manuscript. This work is supported through an Environment and Conservation
Fund from the government of Hong Kong (ECF
Project 32-2015).
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ASIAN MYRMECOLOGY
A Journal of the International Network for the Study of Asian Ants
Communicating Editor: Christian Peeters