Parasite Lost: Chemical and Visual Cues Used by Pseudacteon in Search of Azteca instabilis
Kaitlyn A. Mathis
Stacy M. Philpott
Rayane F. Moreira
R. F. Moreira Department of Natural Science, Hampshire College
, 893 West St., Amherst,
MA 01002, USA
S. M. Philpott Department of Environmental Sciences, University of Toledo
, 2801 W. Bancroft Street, Toledo,
OH 43606, USA
) University of California
, 137 Mulford Hall,
Berkeley, CA 94720, USA
An undescribed species of phorid fly (genus: Pseudacteon) parasitizes the ant Azteca instabilis F Smith, by first locating these ants through the use of both chemical and visual cues. Experiments were performed in Chiapas, Mexico to examine a) the anatomical source of phorid attractants, b) the specific chemicals produced that attract phorids, and c) the nature of the visual cues used by phorids to locate the ants. We determined that phorid-attracting chemicals were present within the dorsal section of the abdomen, the location of the pygidial gland. Further experiments indicate that a pygidial gland compound, 1-acetyl-2-methylcyclopentane, is at least partially responsible for attracting phorid flies to their host. Finally, although visual cues such as movement were important for host location, size and color of objects did not influence the frequency with which phorids attacked moving targets.
Parasitoids have evolved effective and efficient methods of host location, many of
which involve utilization of chemical and visual cues. Social insects, such as ants,
use chemical communication as a primary form of interaction along with some
visual and tactile signals (Jackson and Morgan 1993; Hlldobler 1999). The
chemical signals exchanged between ants are often complex and species specific
(Jackson and Morgan 1993). The reliability of these intraspecific chemical signals
thus makes them effective host location cues for ant parasitoids such as phorid flies
(Brown and Feener 1991; Feener et al. 1996; Morehead and Feener 2000).
Many dipteran parasitoids in the family Phoridae use ants as hosts (Disney 1994).
These phorid species are commonly referred to as the decapitating flies. In
Pseudacteon species phorid flies that attack Solenopsis, the adult flies hover over
ant hosts and dive down to oviposit an egg beneath the ants exoskeleton. The larva
hatches and moves through the ant into the head where it eats the contents and uses
the empty shell as a case in which to pupate, eventually causing the ants head to fall
off (Cnsoli et al. 2001). Later, the adult phorid fly will emerge from the head of the
dead ant to begin the cycle again (Porter 1998; Disney 1994). Although phorids have
direct parasitic effects on ants (i.e. cause ant mortality), they also significantly
change ant foraging behavior by limiting host resource acquisition behavior,
modifying ant competitive hierarchies, and dampening ant effects on herbivores
(Feener 1981; Feener and Brown 1992; Orr et al. 1995; Vandermeer et al. 2002;
A number of different phorid-ant relationships have been described and, for each,
it is generally reported that phorids use chemical and visual cues to locate ant hosts,
but the specific cues used by phorid species to locate particular ants differ (Feener
et al. 1996; Morehead and Feener 2000; Vander Meer and Porter 2002; Chen et al.
2009; Maschwitz et al. 2008; Gazal et al. 2009). Ants produce a range of
pheromones with different functions in different glands throughout their bodies.
These pheromones are responsible for behaviors such as trail marking, worker
recruitment, and alarm signaling, each of which has been linked to attracting
phorids. For example, the phorid parasitoid, Apocephalus paraponerae Borgmeier, is
attracted to 4-methyl-3-heptanone and 4-methyl-3-heptanol produced in the
mandibular glands of its host, Paraponera clavata Fabricius (Feener et al. 1996).
The thoraces of ants contain the metaplural glands, which are the source of the
kairomone known to attract Pseudacteon tricuspis Borgmeier to Solenopsis invicta
Buren (Chen and Fadamiro 2007). The abdomens of ants also contain several glands
that produce pheromones, although to our knowledge no compounds present within
abdominal glands have previously been reported as phorid attractants.
The small amount of information reported on visual cues used by phorid flies
indicates that these cues can also vary based on individual phorid-ant relationships.
Some phorids oviposit on stationary hosts, whereas others require host motion
(Wuellner et al. 2002). Other phorids select hosts based on host size or color (Owens
and Prokopy 1986). For example, Apocephalus paraponerae attack stationary
individuals preferring hosts with large body size (Moorehead and Feener 2000).
Neodohrniphora curvinervis Malloch, a parasitoid of Atta cephalotes Linnaeus, also
prefer larger worker castes as hosts (Orr 1992). Preference for larger hosts also
occurs in Pseudacteon crawfordi Coquillett, a parasitoid of fire ants (however based
on range phorid species might be Pseudacteon hippeus Plowes) (Feener 1987;
Plowes et al. 2009).
One of the more recently described ant-phorid relationships is that between
Azteca instabilis and an undescribed species of Pseudacteon. Azteca instabilis is an
aggressive arboreal ant species ubiquitous over the New World tropics. On coffee
plantations, these ants commonly create carton nests in the large shade trees and
forage in the coffee plants surrounding the nest. Azteca instabilis tends scale insects
living on coffee bushes and preys on other insect herbivores of the coffee leaves
(Perfecto and Vandermeer 2006). The presence of A. instabilis within coffee
plantations has a significant impact on the coffee agroecosystem as a whole and this
species could be considered as a potential biological control agent of coffee herbivores
(Vandermeer et al. 2002; Vandermeer et al. 2008). Presence of Pseudacteon phorid
flies significantly decreases A. instabilis recruitment to resources, affects competitive
interactions with other ant species, and may affect the ability of A. instabilis to control
herbivore populations (Philpott et al. 2004; Philpott 2005a).
A substantial amount of effort has gone into examining the ecology and chemistry
of Pseudacteon-ant relationships. Though Pseudacteon spp. have varying degrees of
host specificity, some phorid species specialize on closely related ant species (Porter
et al. 1995; Gilbert and Morrison 1997; Morrison and Gilbert 1999) With increased
host specificity in the phorid-ant relationship, the chemical and visual cues used in
host location are also likely to be more specific. Based on previous descriptions of
the chemical ecology of ant-phorid relationships, at least two abdominal glands are
putatively important sources of pheromones in A. instabilis. Pavans gland, located
on the ventral side of the abdomen between the 7th and 8th sternites, is the source of
trail pheromones. The pygidial gland, located on the dorsal side of the abdomen
between the 7th and 8th tergites, is significantly larger and contains the pungent
alarm-defense pheromones of the A. instabilis (Do Nascimento et al. 1998). Three
cyclopentyl ketones in their respective concentrations have been reported to be
present in the pygidial glands of A. instabilis (Fig. 1a): 2-methylcyclopentanone
(I), cis-1-acetyl-2-methylcyclopentane (II) and 2-acetyl-3-methylcyclopentene (III)
(Wheeler et al. 1975) (Fig. 1a). However, practically nothing is known about how
Pseudacteon phorid parasitoids orient towards A. instabilis, or the specific chemical
or visual cues driving this relationship.
To amend this lack of information, we examined the chemical and visual cues
acting to attract Pseudacteon phorids to A. instabilis. First we aimed to isolate the
anatomical source of pheromones used by Pseudacteon parasites of A. instabilis by
isolating glandular extracts from ant workers, presenting the extracts near A. instabilis
nests, and observing phorid behavior. Second, using field experiments, we examined
whether pheromones from the aforementioned abdominal glands attract Pseudacteon
parasitoids to A. instabilis, or whether glands from other body parts provide the
necessary chemical cues. We were then able to obtain and make compound I and II
respectively and examined whether one or both act as phorid attractants. Finally, we
investigated the extent to which phorids use visual cues to locate and oviposit on A.
instabilis ants by examining the importance of visual cues such as size, shape, and
color in phorid host choice using life-size moving ant models.
Field work was conducted in the wet season between 27 June and 29 July 2007, and
in the dry season between 7 and 22 February 2008 on a shaded organic coffee farm,
Finca Irlanda, in the Soconusco region of Chiapas, Mexico (15 11 N, 92 20 W).
The farm is located between 950-1,150 m elevation, receives approximately
4,500 mm of precipitation per year, and contains more than 200 species of shade
trees. Mean temperatures during the dry season (MayAugust) range between 19C
and 25C (Lin 2007). There are more than 60 arboreal ant species that occur in the
farm, but A. instabilis is the most frequently encountered on the trunks of canopy
trees (Philpott 2005b). Azteca instabilis builds carton nests on the tree trunks and in
the lower canopy of the trees, and across the landscape, colonies of A. instabilis are
distributed in patches (Vandermeer et al. 2008).
Colony Collection and Description
We collected individuals from four colonies of A. instabilis from areas of the farm
under similar conditions and maintained these partial colonies in the laboratory for
use in making body part extracts. We chose strong colonies with large sections of
accessible carton for collection. In order to collect the nest, we cut as much of the
carton as possible away from the tree and placed it into large plastic boxes, the rims
of which were painted with INSECT-a-SLIP (BioQuip Products, Inc., Rancho
Dominguez, 90220, CA). We collected individuals from two colonies on 27 June
and the others were collected on 4 July. We collected individuals and nest material
from colonies separated by a minimum of 100 m to ensure each were different
colonies, and not satellite nests formed by budding. To confirm the independence of
each lab colony, we placed individuals from each colony directly into tubs
containing others and observed any aggressive behavior.
We provided all colonies with a coffee sapling (potted and under a meter in
height) colonized by scale insects to tend, along with water, tuna, and sugar as
needed. Each of the lab colonies varied in worker size, number of individuals, and in
presence of reproductive individuals. Colony I was the smallest collected colony
with only the smallest caste size of workers (head widths of workers are
approximately 1.1 mm, 1.4 mm, and 2.1 mm for small, medium, and large workers
respectively); no male or female alates were found within the collected carton.
Colonies II-IV contained all worker caste sizes as well as males and winged females.
At the end of the summer field season, all individuals from colony I and II and the
majority of individuals from III and IV were collected in vials, the vials were then
filled with hexanes and placed in the freezer. These preserved ants were then used in
the winter field season for preparation of whole body extracts. Vouchers specimens
of Azteca instabilis and the Pseudacteon phorid flies have been deposited at El
Colegio de la Fontera Sur (ECOSUR) in Tapachula, Mexico as well as the
University of Toledo in Toledo, OH.
To prepare head, thorax and abdomen extracts, ants were collected from each colony
and frozen until dead. The ants were then trisected into head, thorax and abdomen
sections with razor blades. Fifty heads, thoraxes, and abdomens were placed in
separate 2-dram glass vials with 2 mL of pesticide-grade hexanes and crushed. For
each colony, three extracts of heads, thoraxes and abdomens were prepared for a
total of 12 extracts of each type. To prepare the dorsal and ventral abdominal
extracts, 10 individuals were frozen and their abdomens were bisected under water.
The dorsal and ventral segments were then placed in separate vials, each containing
2 mL of hexanes. When 10 abdomen sections were in each vial, the contents were
pulverized. Colonies II, III, and IV alone were used during these trials as the workers
in colony I were too small to accurately section the abdomens with available
equipment. Three extracts of each body section were prepared from each colony. In
preparation of whole body extracts, 50 previously frozen ants from the colonies were
added to a 2-dram glass vial with 1.5 mL of hexanes and crushed.
Compounds found within the glands of A. instabilis as well as another general ant
alarm compound were diluted and prepared to use for observations with phorid flies.
Extracts of 2-methyl-cyclopentanone (I) were prepared using commercially available
2-methyl-cyclopentanone in a 0.17% by volume solution with hexanes (1.5 mL). The
formic acid extract was prepared in a similar manner. 1-acetyl-2-methyl-cyclopentane
(II) was prepared from commercially purchased 1-acetyl-2-methyl-cyclopentene by
reduction of the double bond (Fig. 1b). Diphenylsilane (1.55 mol eq.), anhydrous
ZnCl2 (0.40 mol eq.), and tetrakis triphenylphosphine palladium (1.8 mol%) were
added to IV (60 mg) and ~2 mL of chloroform. The reaction was sealed at room
temperature and allowed to stir overnight. The mixture was purified using column
chromatography on silica gel give a final yield of ~30%. The identity of the final
product, II, was confirmed by GC/MS and 1H NMR.
Preparation of 3-D Model of Swarming Ants
To have the capacity to experimentally isolate chemical from visual cues as phorid
attractants, we prepared a 3-D model of swarming ants to simulate ant movement
without chemical signals. This model consisted of magnets (10 4 mm) placed on a
platform itself sitting atop a magnetic conveyor belt made from bike chain and
powered by a servo motor charged by a 6 V battery (Fig. 2). When in motion, the
magnets move in a pattern that gives the effect of ants swarming in many directions.
To examine visual cues necessary for host location and oviposition, we prepared two
different types of model ants to place on the magnets and magnetic platform to attract
Fig. 2 Schematic diagram of the 3-D swarming ant model. A: Magnets (with or without clay ants/dead A.
instabilis) observed for phorid attack. B: The platform the magnets move across in a seemingly random
pattern. During trials the platform rests directly on top of the rest of the mechanism. C: 2 dram screw cap
vial containing 50 crushed A. instabilis workers in hexanes and a filter paper wick. D: The other half of the
magnets attached to the bike chain beneath the platform. E: The sprockets that guide the bike chain as it is
propelled by the motor. F: The bike chain. G: 6 V battery used as a power source for the motor. H: Servo
Motor. I: Dial that will increase or decrease resistance, effectively acting as a power switch as well as
allowing the operator to control the speed of the ant model magnets
phorids. We used freshly killed A. instabilis and ant-shaped clay models on the
platform of our model. Ants used in visual cue observations were collected fresh from
A. instabilis nests and frozen until dead. To examine whether size of host matters for
Pseudacteon parasites of A. instabilis, we collected individuals from the largest
(5 mm), middle (3-4 mm) and smallest (<3 mm) caste size for our experiments. We
then washed these ants with hexanes to remove cuticular hydrocarbons or any other
chemical cues that may be of further use to the phorids in host location. Once dry, we
attached the ants to rectangular magnets using gorilla glue (The Gorilla Glue Co.,
45227, OH). To examine whether color is an important visual cue for Pseudacteon
parasites of A. instabilis, we molded red, yellow and brown ant shapes (approximately
5 mm in size) out of Fimo dough (Eberhard Faber, 91311, CA) and glued them to
small square magnets to make ant models for color choice tests. Azteca instabilis ants
most closely match the red color used in clay models. We prepared fresh versions of
these models every day this type of observation was performed.
During the summer field season, we placed extracts made from different A. instabilis
body parts near A. instabilis nests to record phorid attraction. Twelve strong A.
instabilis colonies, defined as those with between 530 workers foraging at the base
of the nest, each separated by at least 30 m were used as trial sites. To deliver
pheromone into the air surrounding the nest, we placed open vials containing the
prepared extract, with a filter paper wick, near the base of the nest. We presented
each of the five extract types (head, thorax, abdomen, ventral abdominal section,
dorsal abdominal section) on different days to prevent any potential contamination
or any possible synergistic effects due to the presence of multiple compounds. On a
sixth day, wicks doused in solvent controls were presented at A. instabilis colonies.
To prevent differences between ant activities at each observation site from affecting
the outcome, each field colony was visited each day at approximately the same time,
and in the same order. The source of the extracts (i.e. lab colony) presented to each
colony was randomized to account for any possible differences in extracts
(concentration, composition) produced by individual lab colonies.
After presenting extracts to the air, the area surrounding the vials (approximately
30 cm2) was observed for 10 min and any phorid attack sessions were recorded. The
phorid flies tend to attack by hovering over a moving ant, then diving at the ant between
approximately 1 and 30 times before leaving the trial site. We considered independent
phorid attack sessions to be any time in which the phorid fly approached the vial, then
hovered over a single ant and dove toward the ant at least once. Multiple attacks on the
same ant directly after one another were counted as the same attack session.
During the winter field season, we performed 15 min observations with extracts
of whole body A. instabilis, along with formic acid, compound I, and compound II
(each 0.17% by volume in 1.5 mL hexanes). Due to relative availability of the extract
types, sample size differed for each of the extracts. We observed eleven replicates
with compound I, nine with formic acid, six using compound II, six with and whole
body extract. Otherwise, observation methods were the same as described above.
To examine visual cues used by phorids, we placed the 3-D swarming ant model
within one meter of a strong colony of A. instabilis. We then added to the center of the
platform, 6 model ants (either two of each color (yellow, brown, and red) or two of
each size (small, medium, and large), along with a vial containing extract prepared
from whole bodies of A. instabilis (Fig. 2). Extract preparation and set up of wires
required several minutes during which the model ants remained stationary on the
platform and vials with extracts remained closed. It is important to note that no phorid
flies appeared until the extract of 50 crushed workers was opened and no flies attacked
a model until the motor was turned on. To begin a 15 min observation period, we
turned on the motor after opening the extract vial and inserting the filter paper wick.
During observations, we recorded the number of phorid attack sessions on each ant
type. As a control, we placed 6 magnets without ant models on the platform, along
with the whole body extract and observed the number of phorid attack sessions on
moving magnets for 15 min. Additional control observations were performed with each
model type where the models remained stationary throughout the 15 min observation
period. We performed 12 replicates each of type of visual cue choice (size, color, and
control observations as well as a duplicate set of no movement control observations).
The five extract types as well as the abdominal extracts were compared using a
Chisquare test of proportions. Additionally, the number of phorid attack sessions for
each chemical and visual cue was compared using univariate ANOVAs and Tukey
post hoc tests. We used ANOVA to compare the number of phorid attack sessions
depending on a) chemical cues presented to phorids, b) size of visual cues, c) color
of visual cues, and d) type of visual cue (dead ant, clay, control). In order to meet
conditions of normality, all data were log-transformed (ln (1+ number of phorid
Of the five anatomical extracts and solvent control presented at A. instabilis
colonies, only the abdomen extract attracted phorid flies (Table 1). Moreover, the
extracts prepared from the dorsal portion of the abdomen attracted more phorid flies
than extracts prepared from the ventral portion. These results suggest that the
chemical attractant(s) is located within the dorsal portion of the abdomen
(ChiSquare = 268, df = 4, P= 0.001).
Two compounds known to be present within the pygidial glands of A. instabilis
were then tested. While compound I did not attract phorid flies, compound II
attracted phorid flies. However, whole body extracts of 50 A. instabilis attracted
significantly more phorid flies than the 1-acetyl-2-methylcyclopentane (II) extracts
(F = 25.774, df = 3, P= 0.001; Fig. 3). During trials with compound II a small
percentage of foraging ants (<5 on average) were observed aggregating near the
foreign vial and attacking it. To ensure the potential alarm responses of these
foraging ants were not attracting phorids, formic acid extracts were also presented at
trial sites to disturb the ants and induce an alarm response. These extracts attracted a
slightly larger number of foraging A. instabilis (approximately 710 on average) that
attacked the vials in a similar manner as those in compound II trials. However, no
phorid flies were observed during the trials with formic acid, indicating that phorids
Table 1 Total number of phorid flies attracted to head, thorax, abdomen, dorsal abdomen section and
ventral abdomen section extracts of A. instabilis as well as whole uncrushed ants in hexanes and a hexane
control. Total number of trials=84
Total number of attack sessions per extract type and colony number
observed during compound II trials were attracted by compound II alone. Ants were
observed to assume defensive postures due to presentation of both
1-acetyl-2methylcyclopentane and formic acid, but no phorid flies were observed during the
formic acid extract observations, indicating that presence of phorids during
1-acetyl2-methylcyclopentane observations was due to the extract alone.
Phorid flies did not attack the models when stationary and only a very small number
of phorids attacked the moving magnets alone (Fig. 4a). This indicated that these
phorid flies need some type of visual cue resembling their host ant to orient and
attack. However, size and color do not appear to be critical components of the visual
cue (Fig. 4b, c). During our observations, numbers of phorid fly attacks on the clay
model ants as well as the dead A. instabilis did not differ, but phorids attacked
models more than 10 times more often that magnets alone (F = 4.842, df = 2, P < 0.03).
However, the phorid flies had no significant preference with respect to size of dead
ants (F = 0.783, df = 3, P > 0.5) or color of clay models (F = 0.071, df = 2, P > 0.9).
Our results give strong evidence that this species of Pseudacteon uses pheromones
produced in the dorsal portion of A. instabilis abdomens as host location cues. In
only one trial out of a total of 9 observations, a ventral extract attracted a single
phorid fly. This outlier is likely the result of a contamination of the extract during the
abdomen bisection rather than resulting from trail compounds within the Pavans
gland attracting phorids to their hosts. Overall, the abdominal extracts attracted a
larger number of phorid flies per trial than the dorsal extracts; however, abdomen
extracts contained 5 times more A. instabilis individuals than the extracts made from
dorsal sections of the abdomens alone. This result possibly indicates a correlation
between A. instabilis and phorid fly densities, consistent with previous studies
(Vandermeer et al. 2008; Philpott et al. 2009).
Fig. 4 Average number of phorid attack sessions on different visual cues presented to Pseudacton phorids
at Azteca instabilis colonies. Phorid responses were compared based on type of cue presented both with
and without movement of the models (a), size of visual cue (b), and color of visual cue (c). Bars with the
same letters are not significantly different at P=0.05)
Alarm-defense pheromones are emitted from the pygidial gland of Azteca spp. ants
(Wheeler et al. 1975). Furthermore, the use of alarm-defense pheromone in phorid
host location is consistent with observations at Finca Irlanda. The alarm-defense
pheromones of A. instabilis, very easily triggered by nest disturbance, smell strongly
of blue cheese, thus it is easy to detect whether the ants have emitted alarm-defense
compounds. Phorid flies are far easier to locate near an A. instabilis nest after the nest
has been disturbed in some way (generally by blowing on the nest or poking it with a
stick). Within seconds of nest disturbance the characteristic odor of A. instabilis can be
detected and often within minutes multiple phorid flies can be seen attacking the
swarming A. instabilis. Furthermore, in other studies with phorid flies and A.
instabilis, phorids are observed attacking their host species at tuna baits. This
observation is also potentially consistent with our data as baits are generally forums for
competitive interactions between A. instabilis and other species of ants (LeBrun and
Feener 2002; Orr et al. 2003; Morrison and King 2004; Philpott 2005b). These
interspecific interactions may induce the production of alarm-defense pheromones,
thus attracting phorid flies to baits with multiple ant species competing for resources.
Chemical Extracts and Whole Body Extracts
While cis-1-acetyl-2-methyl-cyclopentane (II) was found to attract phorid flies, the
relative abundance of phorid attack sessions was small when compared to
observations using whole body extracts. This result could be an effect of relative
concentration of the chemical compound used or it may be possible that another
compound within the pygidial gland of A. instabilis is also an important attractant of
phorid flies. Apocephalus paraponerae, for example, are attracted to a mixture of
4methyl-3-heptanone and 4-methyl-3-heptanol in a 9:1 ratio (Feener et al. 1996;
Moorehead and Feener 2000). Furthermore, phorid flies were not attracted to model
ants where formic acid was presented although nearby foraging ants became visibly
alarmed with the use of both the formic acid and compound II. To control for alarm
responses of foraging ants caused by alarm-defense compound extracts, formic acid
extract was tested at trial sites. Though foraging ants produced a typical alarm
response, it was not strong enough to attract phorid flies during the 15 min trials.
Therefore while foraging ants at trial sites with compound II were producing alarm
responses, it is unlikely that these alarm responses were responsible for phorid
Movement, Size, Shape and Color Cues
Other species of Pseudacteon are reported to use a hierarchy of chemical and visual
cues in host location (Moorehead and Feener 2000). While this Pseudacteon sp.
appears to require motion and an approximately ant shaped form in order to hover
over and attack a host, these phorids do not appear to be very specific as to what
they will attack as long as the correct chemical attractant is present. Phorids, like
many other taxa, thus require multisensory (chemical and visual) cues to locate hosts
(Partan and Marler 2002). Phorids were as almost equally as likely to attack any of
the clay models, indicating that color is not a crucial factor in host choice. Ant
models of the smallest, middle and largest caste sizes were all equally attacked as
well. Moreover the clay models, although less realistic, were as effective as the dead
ant models at attracting flies. Indeed, clay models had slightly more phorid attack
sessions than the dead A. instabilis individuals. In order to fully understand the
visual cues used by this species of Pseudacteon, other aspects such as speed of the
host should be taken into consideration. The speed of the ant models on the conveyer
belt was kept constant in the experiment, but could be varied in future studies.
A substantial amount of effort has gone into examining the relationship between fire
ants and their Pseudacteon parasitoids with the hope that phorid flies will be an
effective biological control agent against this invasive species (Chen and Fadamiro
2007; Feener and Brown 1992; Morrison and Gilbert 1999; Morrison and King
2004; Morrison and Porter 2006). In the case of A. instabilis, however, a high level
of foraging activity is important in coffee agroecosystems where A. instabilis acts as
a biological control agent for coffee pests. A better understanding of the chemicals
attracting Pseudacteon to A. instabilis may potentially elucidate whether these
compounds could be utilized as a bait in phorid traps placed on coffee farms to ease
the effects of phorid flies on A. instabilis foraging and survival in order to promote
the ants defense of the coffee plants. Similar traps have been designed for other
systems (Puckett et al. 2007). However, further investigation into the nature of the
chemical attractants such as required concentration of cis-1-acetyl-2-cyclopentane,
information on whether compound III or any other additional compound in the
pygidial gland works as a synergistic attractant, and a better understanding of the
distance with which phorid flies are able to detect this compound (or potential
compounds) is needed before baited phorid traps could be effectively constructed.
Acknowledgments We thank G. Lpez Batista, G. Dominguez, B. Esteban Chilel, and A. de la Mora
Rodriguez for assistance with nest collection along with R. Mesch and V. Finnan for help in the lab. We
thank C. Lentz for assembling the swarming ant model as well as Bernardo and Walter Peters for granting
us permission to work at Finca Irlanda. Also thanks to B. Schultz, M. Feinstein, S. Partan, and for
providing helpful comments. This research was funded in part by NSF grant DEB 0349388 to
J. Vandermeer and I. Perfecto, The University of Toledo, and the Ray Coppinger Fund. These experiments
comply with the current laws of Mexico, the location in which they were performed.
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