Fire Ant Detecting Canines Complementary Method in Detecting by liaoqinmei


									                                                 HOUSEHOLD AND STRUCTURAL INSECTS

             Fire Ant-Detecting Canines: A Complementary Method in
                        Detecting Red Imported Fire Ants
                 YU-LING KUNG,1 YI-YANG LIEN,5,6 AND YANG-YUAN CHEN1,7

                                  J. Econ. Entomol. 104(1): 225Ð231 (2011); DOI: 10.1603/EC10298
      ABSTRACT In this investigation, detection dogs are trained and used in identifying red imported
      Þre ants, Solenopsis invicta Buren, and their nests. The methodology could assist in reducing the
      frequency and scope of chemical treatments for red imported Þre ant management and thus reduce
      labor costs and chemical use as well as improve control and quarantine efÞciency. Three dogs
      previously trained for customs quarantine were retrained to detect the scents of red imported Þre ants.
      After passing tests involving different numbers of live red imported Þre ants and three other ant
      speciesÑCrematogaster rogenhoferi Mayr, Paratrechina longicornis Latreille, and Pheidole megacephala
      F.Ñplaced in containers, a joint Þeld survey for red imported Þre ant nests by detection dogs and bait
      traps was conducted to demonstrate their use as a supplement to conventional detection methods. The
      most signiÞcant Þndings in this report are 1) with 10 or more red imported Þre ants in scent containers,
      the dogs had 98% chance in tracing the red imported Þre ant. Upon the introduction of other ant
      species, the dogs still achieved on average, a 93% correct red imported Þre ant indication rate.
      Moreover, the dogs demonstrated great competence in pinpointing emerging and smaller red im-
      ported Þre ant nests in red imported Þre ant-infested areas that had been previously conÞrmed by bait
      trap stations. 2) Along with the bait trap method, we also discovered that 90% of red imported Þre
      ants foraged within a distance of 14 m away from their nests. The results prove detection dogs to be
      most effective for red imported Þre ant control in areas that have been previously treated with
      pesticides and therefore containing a low density of remaining red imported Þre ant nests. Further-
      more, as a complement to other red imported Þre ant monitoring methods, this strategy will signif-
      icantly increase the efÞcacy of red imported Þre ant control in cases of individual mount treatment.

      KEY WORDS red imported Þre ant, bait trap station, detection dog, odor recognition, Þre ant

The red imported Þre ant, Solenopsis invicta Buren, an                        This notorious pest is capable of consuming a large
exotic species that originated from South America,                         quantity of food during its rapid propagation, devas-
was Þrst discovered in the United States in the 1920s.                     tating agricultural products, threatening the well-be-
Their spread to pan-PaciÞc countries such as Australia,                    ing of both livestock and humans, and seriously af-
New Zealand, Taiwan, and China took place around                           fecting the native animal species in the invaded areas
the early 21st century (Callcott and Collins 1996, ISSG                    (Adams 1986, Lofgren 1986, Allen et al. 1994).
2010). Morrison et al. (2004) also predicted, based on                        The application of ant baits containing toxic chem-
their dynamic ecophysiological model of colony                             icals or insect growth regulators (IGRs) over the in-
growth, the path of the red imported Þre antÕs future                      fested areas is one of the most widely adopted strat-
invasions to parts of Asia, Africa, southern Europe, and                   egies in red imported Þre ant management. Dust,
even to the PaciÞc island nations.                                         granule, or liquid insecticide intended for individual
                                                                           mount treatments also provide a quicker option for
   1 Institute of Physics, Academia Sinica, Taipei, 128 Sec. 2, Academia   small-scale pest control. The red imported Þre ant
Rd., Nankang, 11592, Taiwan.                                               control support services in the United States have
   2 These authors contributed equally to this work.                       promoted a methodology combining broad-spectrum
   3 Working Dog Training School, National Pingtung University of
                                                                           and single-nest treatment, known as the “two-step
Science and Technology, 1, Shuefu Rd., Neipu, Pingtung, 91201, Tai-
                                                                           method.” The two-step method is presently consid-
   4 Department of Biology, National Changhua University of Educa-         ered as the most cost-effective and environmentally
tion, 1, Jin-De Rd., Changhua City, 50007, Taiwan.                         friendly approach for highly red imported Þre ant-
   5 Department of Veterinary Medicine, National Pingtung Univer-
                                                                           infested areas (Drees et al. 1998, 2000). However,
sity of Science and Technology, 1, Shuefu Rd., Neipu, Pingtung, 91201,
                                                                           Drees reported that the overuse of the red imported
   6 Corresponding author, e-mail:               Þre ant pesticide “diazinon” produced massive
   7 Corresponding author, e-mail:              amounts of waste and water pollutants that failed to

                                                                    0022-0493/11/0225Ð0231$04.00/0   2011 Entomological Society of America
226                               JOURNAL OF ECONOMIC ENTOMOLOGY                                      Vol. 104, no. 1

pass the state and federal discharge standards in the        of varying quantity; discriminate them from other ant
United States (Drees 2003). Moreover, related re-            species; and perform a detailed Þeld investigation of
search revealed that contaminated drainage ditches           emerging and small red imported Þre ant nests in a
from the long-term insecticide applications might al-        pretreated outdoor area, which provided the ground-
ter the water quality of streams and rivers and affect       work needed for the posttreatment of these individual
the aquatic communities (Heckman 1981, Liess and             mounts.
Schulz 1999). Therefore, an accurate assessment of
the level of red imported Þre ant infestation is needed
                                                                             Materials and Methods
before more precise insecticide treatments can be
applied as to reduce both the environmental and eco-            Red Imported Fire Ants. Red imported Þre ants for
nomical costs associated with chemical control.              dog training were collected from mounds in Ching-Pu,
   In monitoring red imported Þre ant, visual inspec-        Taoyuan County, Taiwan. This was done by placing
tion, pitfall traps, and bait traps are the most common      pieces of tissue paper upon the disturbed mounds,
methods adopted in detecting the red imported Þre            thereby allowing the collection of the ants that ag-
ant and determining the amount of treatment. For             gressively swarmed the paper. The red imported Þre
large-scale investigations, satellite imagery, aerial im-    ant populated paper was then transferred into plastic
agery, or both are used to provide areawide images of        zip-lock bags where the ants were subsequently anes-
large red imported Þre ant mound distributions (Vogt         thetized with CO2. The paralyzed ants were then
2004a,b). Yet, the nests are usually broken and lack the     placed into a 50-ml capped tube with a square sieved
obvious dune structures on sites where multiple red          opening (1.7 by 1.7 cm) allowing the scent to perme-
imported Þre ant treatments have already been ap-            ate out for dog training and testing.
plied. Many of these areas consist of those that are less       Canines. Three neutered male beagles aged 6, 4, and
tolerant to Þre ant infestation, i.e., places with signif-   2 yr old were recruited in this investigation. They will
icant human activities such as playgrounds, parks, hos-      be referred to as dog A, B, and C, respectively. All
pital, power facilities, and nurseries. Once treated         three dogs had previously received quarantine train-
with pesticides and toxic traps, small amounts of nests      ing to detect agricultural products in airport customs.
may still remain, whereas newer nests also can emerge        The dogs were then further trained for red imported
after treatment. On occasions, nests also are found to       Þre ant detection and used in subsequent experiments.
be concealed in grass sods or outdoor electronic ap-         In the red imported Þre ant training program, the dogs
pliances. Such situations render the visual inspection       were taught to inform their dog handler of red im-
of red imported Þre ant tedious and rather useless. Bait     ported Þre ant presence by sitting in front of the
traps consisting of a food attractant inside a container     discovered targets (passive response).
are not capable of locating the actual site of the              Indoor Training for Red Imported Fire Ant Odor
mounds because they are usually found by foragers;           Recognition and Identification. Red imported Þre ant
instead, they merely show that red imported Þre ant          odor recognition training was initiated indoors as a
exists somewhere within the vicinity of the baits. Thus,     precursor exercise for 2 wk. The purpose of the indoor
individual mound treatment cannot be applied efÞ-            training was to avoid the inßuence of weather and
ciently and accurately to attain rapid red imported Þre      other extrinsic odors commonly encountered out-
ant control in such low nest-density areas. Thus, the        doors. Considering quarantine issues and sample avail-
development of a practical method to rapidly locate          ability, only dead red imported Þre ants were allowed
red imported Þre ant colonies in previously treated          in the indoor training. The indoor training consisted of
areas is necessary as to avoid costs associated with         two steps: 1) 50% of a set of tubes described previ-
inaccurate and ineffective pesticide reapplications.         ously were Þlled with 100 previously frozen red
   Animals rely heavily upon their delicate senses for       imported Þre ants. Each set was then hidden in a metal
survival, such is the case with the dogÕs olfactory sys-     can Þxed on a wooden board. The handler would lead
tem. Taking advantage of this trait, detection dogs are      the dog to sniff the cans that contained the dead red
often trained to search for objects or creatures such as     imported Þre ants and verbally encourage it to sit by
fruit, animal products, snakes, gypsy moths, termites,       the cans; a food reward of two dog biscuit pellets was
bed bugs, and other organisms by tracking their              given for correct responses. Simultaneously, the dogs
unique odors (Wallner and Ellis 1976, Welch 1990,            also were taught not to react to or sit by empty vials
Engeman et al. 1998, Brooks et al. 2003, PÞester et al.      through oral instructions. 2) To prevent dogs from
2008). Dogs have the great capability of accurately          reacting to odors from non-red imported Þre ants, the
locating concealed targets with their nose even when         dogs were further educated to refrain responding to
it is wrapped in packages or enclosed in other mate-         tubes with 100 frozen laboratory reared Solenopsis
rials (Brooks et al. 2003). We had demonstrated pre-         germinata F., Anoplolepis longipes Jerdon, Polyrhachis
viously that dogs were able to pick up the scents of red     dives Smith, Crematogaster rogenhoferi Mayr, or Tet-
imported Þre ants (Huang et al. 2007). In Australia, off     ramorium sp. 1. Before proceeding to the outdoor
leash Labrador retrievers also were trained to freely        training, the dogs are presented with sets of 30 tubes
search for red imported Þre ant nests in the Þeld with       each containing one to Þve tubes of dead red imported
satisfactory results (Corcoran and McNicol 2009).            Þre ants, they must consistently recognize at least 20
   In this report, three beagles were successfully           tubes of red imported Þre ants in total from all the sets
trained on leash to detect live red imported Þre ants        combined. In this case, the number of sets of 30 tubes
February 2011                               LIN ET AL.: FIRE ANT-DETECTING CANINES                                227

presented can vary, but as long as the dog can suc-          Þre ant tubes to be recognized by each dog. “Positive
cessfully identify 20 tubes in total of red imported Þre     indication” was deÞned as a dogÕs correct response of
ants in the duration of the tests, they are allowed to go    sitting by the target red imported Þre ant tubes. The
onto the next training exercise.                             dogsÕ positive indication rates in discerning 100, 50, or
   Outdoor Training for Red Imported Fire Ant Odor           10 ant samples were compared with each other by the
Recognition and Identification. A set of tubes with           MannÐWhitney U test by using the online statistical
100, 50, 10, or no live red imported Þre ants were           analysis package VassarStats as provided by Vassar
buried in a lawn with the lids revealed above the            College (Lowry 2010).
ground. Through the same methodology described                  Ability to Differentiate Red Imported Fire Ants
previously, the dogs were guided to detect the live red      From Other Ant Species. To determine whether the
imported Þre ant-containing tubes and to ignore the          dogs would be confused by unfamiliar ant scents that
empty tubes. To discriminate red imported Þre ant            did not occur in previous training sections, and to
odors from non-red imported Þre ant odors, 100 live          provide them with more chances to recognize other
laboratory raised S. germinata, A. longipes, P. dives, C.    non-red imported Þre ant scents, four sets of 12 metal
rogenhoferi, or Tetramorium sp. 1 were collected in          cans, each containing 10 Þeld-collected C. rogenhoferi,
tubes and arranged randomly during the training.             P. longicornis, P. megacephala, or red imported Þre ants
Dogs were taught to only recognize red imported Þre          were prepared as targets (red imported Þre ant) or
ants and to discriminate them from the non-red im-           nontargets (non-red imported Þre ant species) as de-
ported Þre ant species as in the indoor training.            scribed above. The metal cans were randomly selected
   Field Training for Red Imported Fire Ant Nest             and arranged in a line three meters away from one
Detection. Initially, red imported Þre ant nests varying     another. Each dogÕs distinction ability was assayed
in size were identiÞed in the Þeld by visual inspection.     with the 48 cans once per day for a period of 10 d.
As a warm up, each dog must accomplish two rounds            There were, in total, 120 chances for the red imported
of outdoor live red imported Þre ant training, as de-        Þre ant tubes to be detected by each dog. “Indication”
scribed above, for purposes of recalling their memo-         was deÞned as a dog sitting in front of a can. The
ries about the scents of red imported Þre ants. After        Indication rates of the four species were compared
recollection of their red imported Þre ant odor mem-         with each other by the MannÐWhitney U test.
ories, the dogs were guided to the general area to sniff        Searching for Emerging and Residual Red Im-
out red imported Þre ant nests and to sit by the targets.    ported Fire Ant Nests in the Field Through Detection
Piles of rocks, soil mounds, or nests of non-red im-         Dogs Complemented by the Bait Trap Method. The
ported Þre ant species were selected as negative con-        investigated site is a red imported Þre ant-infested
trols during the training. The dogsÕ false indications of    grassland of 6,160 m2 located at the Taoyuan County
non-red imported Þre ant targets were discouraged            stadium in Taiwan; the stadium had been repeatedly
verbally by their handlers. To avoid being attacked by       treated with pesticides and IGR baits for nearly 2 yr.
red imported Þre ants, dogs also were trained to sit         The ground in the area were without noticeable nest
away from detected nests right after snifÞng.                mounds but contained previously surviving nests and
   Each dog received 2 h of outdoor training in addi-        new emerging nests red imported Þre ant nests that
tion to 2 h of Þeld training each day: one session in the    are hard to detect merely by eye. This grassland is thus
morning and the other session in the afternoon. The          selected for a survey of residual and emerging red
whole process was completed within 2 wk. Alternate           imported Þre ant by detection dogs with the additional
training sessions prevented dogs from being bored and        help of bait trap data.
distracted from the work, which could lead to lower             The grassland was equally divided into seven
efÞciency during training. Field training also provided      smaller subareas, each 880 m2. First, for bait traps,
more complicated situations that sharpened their ca-            220 uncapped tubes containing potato chips were
pabilities to pick up more unpredictable scents of red       distributed equally to each subarea (with 1,540 tubes
imported Þre ants. Before proceeding to the assays of        in total in the whole testing ground). After 2 h, the
the dogsÕ ability in locating red imported Þre ants, they    tubes were collected and capped for further species
must consistently recognizing a combined total of 10         identiÞcation. The number and locations of the tubes
tubes of red imported Þre ants out of sets of tests          were then recorded.
consisting of 30 tubes in an outdoor setting, just as they      Second, the dog handler led the dogs to search for
did before proceeding to the outdoor training.               red imported Þre ant in the same area immediately
   Olfactory Detection of Varying Numbers of Red             after the completion and removal of the baits traps.
Imported Fire Ants. Fifteen tubes of red imported Þre        Dogs A and B were selected for the detection process.
ant were prepared as targets, in which three sets of Þve     Places containing 10 red imported Þre ants were
tubes each contained 100, 50, and 10 live red imported       deÞned as an ant nest. Sites of detected red imported
Þre ants. A further 45 empty tubes were used as non-         Þre ant nests (as opposed to forage tunnels) were
targets. Tubes were randomly selected and buried in          further veriÞed by shovel excavation or potato chip
the ground in a line, 3 m away from one another with         bating, and the number of nests was recorded and
their lids exposed to the air. Each dog was assayed with     mapped on the same plot mentioned above.
the 60 (15 red imported Þre ants 45 empty) tubes                The whole procedure ended in 7 d, with the
once per day, for a period of 10 d. There were, in total,    6,160-m2 area fully investigated, resulting in a com-
50 chances for each of the 10, 50, and 100 red imported      plete map of the red imported Þre ant distribution as
228                                JOURNAL OF ECONOMIC ENTOMOLOGY                                          Vol. 104, no. 1

   Fig. 1. Distribution of bait trapped red imported Þre ants (open circles) and dog-detected red imported Þre ant nests
(closed squares) on the site of interest. The dotted line enclosed region illustrates the area that was searched using the
detection dogÐbait trap method.

revealed by the bait trap data combined with the nest         empty tubes. In this category, the false positive indi-
detection data from the dogs (Fig. 1).                        cation rate was 2% for each dog. We also observed
   For data analysis, a grid with cells of 2 by 2 m was       a lack of signiÞcant difference among the dogsÕ abil-
superimposed onto the map of the surveyed area to             ities in detecting red imported Þre ants. Overall, the
measure distances between the bait trapped red im-            results indicate that all three trained detection dogs
ported Þre ant and their nest sites. Concentric circles       were able to detect red imported Þre ant populations
centered at red imported Þre ant nests with various           of 10 ants. This threshold is preferable for locating
radiuses from 0 to 18 m were plotted at increments of         grouped red imported Þre ants or red imported Þre ant
2 m. The larger the plotted circle area, the more             nests rather than solo foragers.
trapped red imported Þre ants were included within               Assessment of the Dog’s Ability to Distinguish Red
its radius. The percentage of trapped red imported Þre        Imported Fire Ant From the Other Species. Four ant
ants in each radius was then calculated from the num-         species, C. rogenhoferi, P. longicornis, P. megacephala,
ber of trapped red imported Þre ants in each extending        and red imported Þre ant, were prepared and tested.
radius over the total number of trapped red imported          Ten ants from each species were presented alive to the
Þre ants in the entire survey area. A logarithmic re-         detection dogs as described in Materials and Methods.
gression curve of the accumulation percentage of red          The general correct indication rate on red imported
imported Þre ants versus radii was generated to show          Þre ant by the dogs was 93%. This result is signiÞ-
their correlation.

   Dogs’ Olfactory Ability in Discerning Various
Quantities of Red Imported Fire Ants. The experi-
mental data were separated into two parts and ana-
lyzed as follows: one part was the detection dogsÕ
reaction toward the tubes which contained 10, 50, or
100 live red imported Þre ants. Positive indications
were deÞned as when the dogs successfully located
the tubes containing red imported Þre ants. All three
trained detection dogs were capable of locating the
red imported Þre ant tubes, with an overall positive
indication rate of 98% (Fig. 2). There were no sig-               Fig. 2. Positive indication rates of detection dogs for red
                                                              imported red ants (RIFA) in tubes containing 10, 50, and 100
niÞcant difference between dogs and their capabilities        ants. Positive indication rate is the mean percentage of pos-
of detecting 10, 50, or 100 ants (P      0.05; MannÐ          itive indications over total indications by dogs. The result
Whitney U test). The other part was the results of the        shows no signiÞcant differences among the dogsÕ capability
detection dogsÕ responses to empty tubes. False pos-          in discriminating the varying quantities of ants (P       0.05;
itive indication is deÞned as when the dogs reacted to        MannÐWhitney U test).
February 2011                               LIN ET AL.: FIRE ANT-DETECTING CANINES                                                                                       229

                                                                                                                                                                  ( )
                                                                                                                                                     y = 0.1538Ln(x) + 0.4985
                                                                                                                                                            R2 = 0.976
                                                                                                               120%                  ( 13.6 , 90%)

                                                              % of numbers of trapped
                                                                                        RIFA in circle areas
                                                                                                                      0   2    4    6    8   10      12   14   16   18   20

                                                                                                                      Radius extended from dog detected ant nest ( m )

                                                                 Fig. 4. Relationship between the dog-detected ant nests
                                                              and the bait-trapped red imported Þre ants (RIFA). Open
                                                              circles, percentage of trapped RIFA located in different radii
                                                              extended from the nests. An arrow indicates that 90% of
                                                              trapped RIFA were located within 14 m from the nests.

                                                              From the experimental results, it was concluded that
                                                              most of the red imported Þre ants ( 90%) were
                                                              foraging within 14 m from the nests and that only
                                                                10% red imported Þre ants foraged at distances fur-
                                                              ther than 14 m. The longest observed distance covered
                                                              by ants foraging from the nearest nest was 26 m.

   Fig. 3. Percentage of indication rates for the four ant       All three trained dogs demonstrated high positive
species by detection dogs. Indication rate is the number of   indication rates ( 98%) in detecting red imported Þre
dog indicated tubes over the total tube numbers. Columns      ants. Their false positive rates on the empty tubes were
represent the mean SD of 10 repetitive tests. The asterisks     2%. The indication rate on C. rogenhoferi, P. longi-
indicate the signiÞcant difference between the non-red im-    cornis, and P. megacephala were also 4%. All these
ported Þre ant species and red imported Þre ants (P 0.05;     results not only suggest the great capability of dogs for
MannÐWhitney U test).                                         locating red imported Þre ant but also met the re-
                                                              quired minimum acceptable detection threshold
cantly higher (P 0.05; MannÐWhitney U test) than              among other insect detection dogs as suggested by
the 4% from the dogsÕ response to other species (Fig.         Brooks et al. (2003). In his report, the termite detec-
3). The results revealed that, after training, the three      tion dogs had an accuracy of 95.93% in detecting east-
detection dogs had all acquired the capability to cor-        ern subterranean termites, Reticulitermes flavipes
rectly differentiate red imported Þre ants from the           (Kollar). Bed bug-detecting dogs showed an accuracy
other local species of ants.                                  of 97.5% in locating live bed bugs as well as a 90.0%
   Detection Dog and Bait Trap Joint Field Survey.            accuracy in locating viable bed bug eggs (PÞester et
Twenty-Þve tubes of trapped red imported Þre ants             al. 2008). A trained German wirehaired pointer could
were captured by bait traps and 13 nests were located         search for screwworms, Cochliomyia hominivorax
by the dogs (Fig. 1). Besides this, we also found tubes       (Coquerel), with 99% positive indication rate, and
occupied by other non-red imported Þre ant ants, with         three German shepherds were able to sniff out the
numbers from a few to hundreds depending on the               gypsy moth, Lymantria dispar (L.), egg masses with an
tubesÕ location and the geological distribution of the        accuracy of 95% (Welch 1990, Wallner and Ellis 1976).
different species of ants. The total number of tubes             Many factors may affect the detection accuracy of
with non-red imported Þre ants was estimated to               the dogs, ranging from the training protocols, equip-
be 30% out of the 1,540 tubes.                                ment, abiotic factors such as temperature and wind,
   According to the logarithmic regression curve              and the maintenance of the dogsÕ memories toward
(R2 0.976) showing the percentage of accumulated              speciÞc odors. The handlerÕs interpretation of the
bait trapped red imported Þre ant in the circled area         dogÕs behavior as well as the length of dogÕs detection
versus the radii, 60% of captured red imported Þre ants       time also contributed to their effectiveness (Wallner
were located within a 2-m radius centered at the              and Ellis 1976, Welch 1990). Although all three dogs
closest nest. As the radius extended to 14 m, almost          received the same training process and maintenance
90% of captured red imported Þre ant were included            and were tested under identical conditions, dog CÕs
in the circle. Thus, only 10% of the red imported Þre         positive indication rates on red imported Þre ant ßuc-
ants wandered to regions outside of the radius of 14          tuated more than the other two dogs. Dog C was
m of the circle centered at the nearest nest (Fig. 4).        observed to become easily excited whenever unfamil-
230                               JOURNAL OF ECONOMIC ENTOMOLOGY                                         Vol. 104, no. 1

iar dogs other than dogs A and B were present, espe-        the potential to improve the accuracy and reduce the
cially in the outdoor environment. Such behavior of-        costs of red imported Þre ant quarantine programs
ten distracted it from active searching and affected the    around the world.
accuracy of detection. Behavioral corrections were            This study was conducted to assess the trained dogsÕ
attempted but were unsuccessful. Considering this,          capabilities in detecting live red imported Þre ants as
only dogs A and B were selected for the Þeld test of        well as their nest in the Þeld. The above-mentioned
investigating the red imported Þre ant nests at the         results indicate that dogs can be trained to detect red
Taoyuan stadium.                                            imported Þre ants, discriminate it from three other
   The Australian canines were taken off their leashes      species, and locate red imported Þre ant nests in the
before searching and released to perform free search,       Þeld. Of course, this methodology is by no means a
once the nest is found the dogs wagged their tails          replacement to the conventional detection methods;
excitedly at the site and were subsequently rewarded        instead, the application of the red imported Þre ant
with playtime consisting of catch and retrieve. Our         detection dogs is meant to act as a supplement to the
dogs however were trained to search for Þre ants while      other red imported Þre ant inspection methods by
being guided on leash by a handler; this gives the          providing more accurate identiÞcations of hidden
handler more control over the speciÞc search area and       nests.
the search speed. It also prevents the dogs from getting
too close to the danger of Þre ant swarms and if
necessary, their mouths, noses, and paws can be in-                             Acknowledgments
spected for red imported Þre ant immediately. Fur-             We gratefully acknowledge James Ho (Wichita State Uni-
thermore, a food reward was given instead of playtime       versity, Wichita, KS), Chin-Gi Huang (National Taiwan Uni-
after each successful detection, which ensures that our     versity, Taipei, Taiwan), and Xinyu Toby Huang (Cornell
dogs are well nourished and not too tired or overex-        University, Ithaca, NY) for valuable discussions. We also
cited from playing. Every dog was capable of working        thank Dong-Yi Huang (National Changhua University of
for 4 h/d, dogs that worked over this time frame were       Education) for assistance in Þeld detection of red imported
                                                            Þre ants by bait trap stations and those who provided assis-
less motivated and easily distracted, hence leading to
                                                            tance in this study. The great contributions of the lovely dogs
lower detection rates.                                      Snoopy, Giant, and Johnson in executing the experiment also
   Our Þeld investigation suggests that trapped red         are deeply appreciated.
imported Þre ant were not always adjacent to their
respective nests. Such phenomena could possibly lead
to an over estimation of the red imported Þre ant                                References Cited
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by the bait trap method. Therefore, in practice, ex-           imported Þre ants, pp. 48 Ð57. In C. S. Lofgren and R. K.
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overall positive indication rate of 98% based on the           cidae) in North America from 1918 Ð1995. Fla. Entomol.
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accurate determinations of the speciÞc locations of            Department of Agriculture, Food, and Forestry, Okla-
the individual nests. Once more precise nest site in-          homa City, OK.
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associated with overestimations of nests sites and over        dients used for imported Þre ant control using various
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