ECOLOGY AND BEHAVIOR
Human Urine and Chicken Feces as Fruit Fly (Diptera: Tephritidae)
Attractants for Resource-Poor Fruit Growers
AND JORGE VARO
Instituto de Ecologõ´a, A.C. Apartado Postal 63, 91000 Xalapa, Veracruz, Me´xico
J. Econ. Entomol. 96(2): 334Ð340 (2003)
ABSTRACT Weevaluatedhuman urine and chicken feces, two naturally occurring, inexpensive, and
readily available substances, as baits for the capture of Anastrephaspp. (Diptera: Tephritidae) by using
glass McPhail traps. Two studies were performed simultaneously in a commercial mango orchard in
Veracruz, Me´xico. In the Þrst study, we compared a 50% water dilution of human urine against
hydrolyzed protein, both compounds at the fresh and 5-d-old stages, and water alone (control
treatment). In the second study, we tested fresh chicken feces mixed with water, a torula yeast/borax
solution at three different ages (1Ð4, 5Ð9, and 10Ð15 d), and water (control treatment). Both human
urine and chicken feces were attractive to Anastrepha adults compared with water alone, but attracted
two and three times fewer adults than hydrolyzed protein and torula yeast/borax, respectively.
However, unlike torula yeast/borax, aging of human urine did not decrease its attractiveness. Five-day
old human urine attracted numerically more A. serpentina females than males, similar numbers of
A.obliqua males and females, and signiÞcantly more sexually immature A. obliqua females than mature
ones. Chicken feces proved to be as attractive as the aged torula yeast/borax treatments for A.obliqua
and A. serpentina. We argue that because both human urine and chicken feces are cost-free and can
be easily obtained, they are viable, low-technology alternatives to costly commercial attractants,
particularly for low-income growers or backyard farmers in Mexico and other Latin American
KEY WORDS Anastrepha, Tephritidae, attractants, human urine
AMMONIA IS USED BY several species of fruit ßies
(Diptera: Tephritidae) to locate food and/or ovipo-
sition resources (Bateman and Morton 1981, Mazor et
al. 1987, Epsky and Heath 1998, Robacker 1995,
Robacker and Heath 1996, Hull and Cribb 2001).
Sources of ammonia for potential use as fruit ßy baits
include proteins (Baker et al. 1944, Steiner 1952),
emissions from bacteria (Robacker and Flath 1995,
Robacker and Moreno 1995, Robacker and Bartelt
1997,Robackeret al. 1998, Epsky et al. 1998), and avian
feces (Prokopy et al. 1993, Epsky et al. 1997, Robacker
et al. 2000). Recent investigations on ammonia deriv-
atives have yielded some commercial food-based syn-
thetic lures that have been shown to be particularly
attractive to Anastrepha ludens (Loew) and A. sus-
pensa (Loew). Such ammonia-derived baits include
AMPu (a blend of ammonium bicarbonate, methyl-
amine hydrochloride and 1,4 diaminobutane
[putrescine]) (Robacker and WarÞeld 1993), and
BioLure (a mixture of ammonium acetate and pu-
trescine; Consep Inc., Bend, OR) (Heath et al. 1995,
Thomas et al. 2001). AMPu has been shown to be as
effective as torula yeast (Robacker 1995), and more
attractive than different combinations and concentra-
tions of its own constituents and other amines
(Robacker et al. 1996, 1997). However, in spite of the
fact that some of these food-based synthetic lures
(including the traditional, commercially available hy-
drolyzed protein and torula yeast/borax) have been
proven attractive to some Anastrepha species, the
prospects on their use by low-income Latin American
growers are limited because of cost and accessibility
considerations. The majority of these growers are rep-
resented by subsistence farmers, which require inex-
pensive alternatives for monitoring fruit ßy popula-
tions (Aluja and Liedo 1986; Aluja 1996, 1999).
Two of the most promising, low-cost alternative
baits that have been investigated recently are human
urine and chicken and duck droppings (Hedstro¨m
1988, Prokopy et al. 1993, Epksy et al. 1997, Robacker
et al. 2000). Human urine also releases ammonia (Bell
et al. 1961, Langley 1971, Anonymous 1981), and has
been tested as a potential attractant for Anastrepha
spp. by Hedstro¨m (1988) under Þeld conditions and
by Pin˜ero et al. (2002) in the laboratory with encour-
aging results. Similarly, chicken droppings, which also
Facultad de Agronomõ´a, Universidad Nacional de Colombia, sede
Santa Fe´de Bogota´, Colombia.
0022-0493/03/0334Ð0340$04.00/0 !2003 Entomological Society of America
release ammonia, were more attractive than the
widely used proteinaceous attractant PIB-7 (Staley
Manufacturing Co., Decatur, IL) when tested in Ha-
waii with the Mediterranean fruit ßy (Prokopy et al.
Our aim in this study was to test, under Þeld con-
ditions, the attractiveness to wild Anastrepha spp.
adults of human urine and chicken feces compared
with hydrolyzed protein and torula yeast/borax. Our
long-term goal is to Þnd readily accessible and inex-
pensive low-tech attractants for use in fruit ßy mon-
itoring and control programs in rural areas of Mexico
and other Latin American countries. In these regions,
low-income growers do not produce fruit for national
or international markets, and instead harvest some
clean fruit for in-house consumption or for less-lucra-
tive local markets. Thus, inexpensive traps will be
welcome even if they are not as effective as commer-
cial, high-technology traps.
Materials and Methods
Study Site. Studies were conducted in Apazapan,
Veracruz, Me´xico, from June to August 1993. The
study site is located at 19!19"northern latitude and
96!42"western longitude, at 340 m above sea level.
Climate is characterized as Aw“(W)(i)g (hot, subhu-
mid according to Ko¨ppens classiÞcation system mod-
iÞed by Garcõ´a 1981). Mean annual temperature in
Apazapan is 25.5
C and annual rainfall 1,250 mm.
Tests were conducted in an unsprayed commercial
mango orchard (Mangifera indica L.) ÔManilaÕ. We
selected 10 trees with similar dimensions (height, #10
m, canopy diameter, #9 m), that were #20 m apart
within the orchard. Of these 10 trees, Þve were used
to test human urine and hydrolyzed protein (study 1),
and the rest to test chicken feces and torula yeast/
borax (study 2). For experiments with human urine,
we used hydrolyzed protein because it is the most
commonly used fruitßy bait in Mexico and other Latin
American countries. We used torula yeast/borax as a
positive control in the second experiment to deter-
mine whether a cost-free and readily available sub-
stance such as chicken feces could substitute this ex-
Bait Treatments. In study 1, we evaluated fresh
human urine, 5-d-old human urine, fresh hydrolyzed
protein (Captor Plus; Agroquõ´mica Tridente, S.A. de
C.V. Me´xico, D.F.), 5-d-old hydrolyzed protein, and
tap water (negative control). Human urine was tested
at a concentration of 50% (100 ml of human urine in
100 ml of water) (same concentration used by Hed-
stro¨m 1988). Hydrolyzed protein contained no borax
and wasprepared in a 1:10 dilution. Five-day-old treat-
ments were evaluated to test the effect of aging on
attractiveness. The human urine was from a single
26-yr-old donor (JP), whose diet excluded coffee,
alcohol, vitamin supplements, spicy food condiments,
and tobacco. This diet was maintained throughout the
study period and started 15 d before initiation of trap-
ping. The urea and ammonia contents fell well within
normal ranges (20Ð30 g/100 ml and 0.5Ð0.9 g/100 ml,
respectively; Bell et al. 1961, Anonymous 1981) for a
healthy individual. The complete results of this anal-
ysis are presented in Pin˜ero et al. (2002). Even though
therecan be variabilityin the chemical composition of
human urine because of factors such as age and the
quality and quantity of food ingested (Bell et al. 1961,
Langley 1971, Anonymous 1981), the two components
relevant to us (urea and ammonia), varied relatively
In study 2, bait treatments tested were torula yeast/
borax pellets ERA International, Ltd., Brownsville,
TX) aged over 1Ð4, 5Ð9, or 10Ð15 d, a mixture of fresh
chicken feces and water, and tap water as a negative
control treatment. Torula baits were prepared by dis-
solving four pellets of torula yeast/borax in 200 ml of
water. Pellets weighed #5 g each and torula yeast/
boraxproportion was 4:5. The chicken feces treatment
was prepared by mixing 50 g of fresh chicken feces
(obtained from a local commercial chicken farm the
same days we baited the traps) in 150 ml of water.
Trapping. In each one of the 10 mango trees se-
lected we placed Þve McPhail traps (a total of 50
traps), baited with200 ml of the above-mentioned bait
treatments. Traps were placed in the internal part of
the tree canopies, at #2 m from the periphery. Every
3 d, all ßies captured by traps were removed and
placed in plastic containers containing alcohol (70%)
for their identiÞcation. All traps were then cleaned,
rebaited, and rehung in the trees. Trap position was
rotated every 3 d clockwise within the tree canopies
using a systematic procedure. During every trap-re-
view session we also measured the pH values of Þve
samples (one for each treatment) with a pH tester
(model 59000Ð20; Cole Parmer, Chicago, IL). Overall,
21 trap inspections were performed. All adults cap-
tured were identiÞed to species with the help of an
expert taxonomist (Vicente Herna´ndez-Ortõ´z, Insti-
tuto de Ecologõ´a, A.C.). Females were dissected using
a stereomicroscope to determine the stage of sexual
maturity after the procedures described by Martõ´nez
et al. (1995).
Data Analysis. Data for each study were analyzed
separately. The response variable used was the index
ßies/trap/day, which expresses the daily number of
adults captured per trap (Aluja 1993). To determine
the effect of attractants on captures of A. obliqua and
A. serpentina adults which represented most adults
captured in both studies, we performed an analysis of
variance (ANOVA),on transformed data (square-root
of each value plus 0.5) to homogenize variances, and
followed by a Fisher least signiÞcant difference (LSD)
separation of means procedure (P$0.05). Compar-
isons of pH values were performed separately for each
study by means of ANOVA and LSD tests. For each
species and treatment, we compared the number of
females versus males, and the number of sexually ma-
ture versus immature females captured by traps using
a nonparametric MannÐWhitney Utest. All analyses
were performed using the software Statistica (StatSoft
April 2003 PIN˜ERO ET AL.: HUMAN URINE AND CHICKEN FECES AS FRUIT FLY ATTRACTANTS 335
Bait pH Values. In study 1, average pH values of
both human urine and hydrolyzed protein were not
affected by age, though pH values of both types of
human urine were signiÞcantly higher than those de-
termined for hydrolyzed protein (ANOVA: F$38.2;
df $4, 100; P%0.001) (Fig. 1). In study 2, average pH
values of all torula yeast/borax treatments were
similar, regardless of their age, but pH of chicken
feces was signiÞcantly lower than that of torula
yeast/borax (ANOVA: F$317.0; df $4, 100; P%
0.001) (Fig. 1).
Number of Flies Captured. In study 1, 2,705 adults
of seven Anastrepha species were captured. A. obliqua
was by far the most abundant species, representing
86.9% of total captures, followed by A. serpentina
(11.7%). The other Þve species (A. alveata Stone, A.
chiclayae Greene, A. ludens, A. pallens Coquillett, and
A. striata Schiner) represented 1.4% of the total num-
ber of ßies captured.
Trapsbaited witheither fresh or 5-d-old hydrolyzed
protein captured signiÞcantly more A. obliqua and
A. serpentina adults than human urine-baited traps,
independently of age. All protein and human urine
treatments attracted signiÞcantly more ßies than wa-
ter alone (ANOVA F$17.3; df $4, 495; P%0.001; and
F$10.78; df $4, 495; P%0.001 for A. obliqua and A.
serpentina, respectively) (Fig. 2, study 1).
Fig. 1. pH values (mean &SE) of bait treatments used in both studies: fresh and 5-d-old human urine, fresh and 5-d-old
hydrolyzed protein, and water (study 1), and 1Ð4-, 5Ð9-, and 10Ð15-d-old torula yeast/borax, chicken feces, and water (study
2). Within each study, columns with the same letter are not signiÞcantly different from one another (ANOVA,
Fig. 2. Number (mean ßy/trap/d values &SE) of A.obliqua and A.serpentina adults captured by McPhail traps baited
with either fresh and 5-d-old human urine, fresh and 5-d-old hydrolyzed protein, and water (study 1), or 1Ð4-, 5Ð9-, and
10Ð15-d-old torula yeast/borax, chicken feces, and water (study 2). For each study, data were analyzed separately by ßy
species. Columns withthe same letter within a species andstudy site arenot signiÞcantlydifferent from oneanother (ANOVA,
$0.05; LSD test).
336 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 96, no. 2
In study 2, 3,872 adults of six Anastrepha species
were caught by traps. A. obliqua represented 86.3% of
the total captures, followed by A. serpentina (12%); A.
alveata, A. chiclayae, A. ludens, and A. zuelaniae Stone
represented 1.7% of the total number of ßies captured.
We found a decrease in A. obliqua and A. serpentina
captures as the age of the torula yeast/borax bait
increased. Traps baited with 1Ð4-d-old torula yeast/
borax captured the highest numbers of adults of both
species, followed by traps baited with 5Ð9-d-old torula
yeast/borax. For both species, the chicken feces treat-
ment was found to be as attractive as the 10Ð15-d-old
torula yeast/borax bait (ANOVA F$12.1; df $4, 495;
P%0.001; and F$11.0; df $4, 495; P%0.001, for A.
obliqua and A. serpentina, respectively). Water-baited
traps captured no ßies during the entire study (Fig. 2,
Adult Captures According to Sex. In study 1, all bait
treatments that captured ßies attracted statistically
similar numbers of A. obliqua males and females (Ta-
ble 1, study 1). Both fresh and 5-d-old human urine
attracted numerically more A. serpentina females than
males. In study 2, all bait treatments attracted signif-
icantly more A. obliqua females than males and similar
numbers (no statistical difference) of A. serpentina
females and males (Table 1, study 2).
Sexual Maturity Stage of Captured Females. The
proportion of females caught by traps in study 1, ac-
cording to their stage of sexual maturation, is shown in
Table 2. All bait treatments attracted signiÞcantly
more sexually immature than mature A. obliqua fe-
males. Traps baited with fresh human urine and fresh
and 5-d-old hydrolyzed protein captured signiÞcantly
more immature than mature A. serpentina females. In
study 2, 1Ð4- and 5Ð9-d-old torula yeast/borax at-
tracted signiÞcantly more immature than mature A.
obliqua females (Table 2, study 2). For A. serpentina,
all torula-based treatments and chicken feces at-
tracted numerically, but not statistically, more imma-
ture than mature females.
We found that human urine-baited traps captured
fewer A. obliqua and A. serpentina than protein-baited
traps. There are at least four plausible explanations for
this. First, human urine may be intrinsically less at-
tractive than hydrolyzed protein. Second, the human
urine concentration tested may have exerted some
degree of repellency, as documented by Mazor et al.
(1987) and Robacker et al. (1997) working with C.
capitata and A. ludens, respectively. In both studies, a
negative association was demonstrated between am-
monia concentration and attractiveness to adults. To
address this question, we performed a follow-up study
to determine whether concentration of human urine
had an effect on its attractancy to ßies in the genus
Anastrepha (M. Aluja and J. Pin˜ero, unpub. data). We
found, however, that in most experiments there were
no differences in captures among the three human
urine dilutions tested (50, 25, and 12.5%), and in one
experiment the 50% concentration was the most at-
tractive for A. serpentina and A. obliqua in a sapodilla
orchard, even compared with hydrolyzed protein. In
Table 1. Number of A. obliqua and A. serpentina adults cap-
tured by McPhail traps baited with either fresh and 5-d-old human
urine; fresh and 5-d-old hydrolyzed protein (study 1); or 1-4-, 5-9-,
and 10-15-d-old torula yeast/borax and chicken feces (study 2),
according to the species, bait treatment, and sex. For each bait
treatment and species, statistical comparisons between sexes were
performed using Mann-Whitney Utests (
Bait treatment n%
Fresh human urine 403 55.6 44.4 0.25
5-d-old urine 341 62.8 37.2 0.17
Fresh protein 890 53.5 46.5 0.60
5-d-old protein 716 49.0 51.0 0.92
Fresh human urine 46 65.2 34.8 0.14
5-d-old urine 52 65.4 34.6 0.07
Fresh protein 117 46.1 53.9 0.67
5-d-old protein 101 61.4 38.6 0.14
1Ð4-d-old Torula 1,274 65.5 34.5 0.02
5Ð9-d-old Torula 992 74.2 25.8 0.008
10Ð15-d-old Torula 674 72.3 27.7 0.01
Fresh chicken feces 402 61.9 38.1 0.03
1Ð4-d-old Torula 171 47.4 52.6 0.34
5Ð9-d-old Torula 133 39.1 60.9 0.29
10Ð15-d-old Torula 61 36.1 63.9 0.11
Fresh chicken feces 98 41.8 59.2 0.34
Table 2. Number of A. obliqua and A. serpentina females
captured by McPhail traps baited with either fresh and 5-d-old
human urine; fresh and 5-d-old hydrolyzed protein (study 1); or
1– 4-, 5–9- and 10–15-d-old torula yeast/borax and chicken feces
(study 2), according to the sexual maturity stage. For each bait
treatment and species, statistical comparisons between sexually
immature and mature females were performed using Mann-Whitney
Bait treatment n%
Fresh human urine 207 75.7 24.3 0.008
5-d-old urine 201 76.6 23.4 0.01
Fresh protein 399 79.9 20.1 0.009
5-d-old protein 303 76.3 23.7 0.009
Fresh human urine 27 75.0 25.0 0.02
5-d-old urine 31 67.7 32.3 0.45
Fresh protein 40 80.0 20.0 0.04
5-d-old protein 50 76.0 24.0 0.02
1Ð4-d-old Torula 835 62.1 37.9 0.03
5Ð9-d-old Torula 487 61.5 38.5 0.04
10Ð15-d-old Torula 349 51.3 48.7 0.53
Fresh chicken feces 256 55.2 44.8 0.24
1Ð4-d-old Torula 90 65.5 34.5 0.11
5Ð9-d-old Torula 81 63.0 37.0 0.09
10Ð15-d-old Torula 39 57.5 42.5 0.66
Fresh chicken feces 57 66.7 33.3 0.09
April 2003 PIN˜ERO ET AL.: HUMAN URINE AND CHICKEN FECES AS FRUIT FLY ATTRACTANTS 337
addition, Hedstro¨m (1988) suggested that human
urine at a 50% concentration did not exert any repel-
lent effect to A. obliqua and A. striata adults; in con-
trast, they found that such a concentration of human
urine attracted 10 times more adults of each species
than torula yeast/borax inCosta Rica,even though the
same urine was used over several weeks (without
replacement). Third, pH could have played a role in
rendering hydrolyzed protein and torula yeast/borax
more attractive than human urine and chicken feces,
because pH values of human urine and chicken feces
were signiÞcantly different than those of hydrolyzed
protein and torula yeast/borax. To address this issue,
we plan to conduct a subsequent study in which pH
values of both chicken feces and human urine will be
artiÞcially manipulated and their attractiveness com-
pared to hydrolyzed protein of equal alkalinity.
Fourth, it could be that the ecological characteristics
of the orchards inßuence the degree of response of
ßies in the genus Anastrepha to food-based attractants.
Also, the physiological state of adults (Rull and
Prokopy 2000, Pin˜ero et al. 2002) have to be consid-
ered in the design of more efÞcient monitoring sys-
tems and in the election of appropriate baits.
Herein, fresh human urine attracted large numbers
of A. obliqua and A. serpentina females. A similar trend
was observed in the case of chicken feces for A. obli-
qua. Thus, both human urine and chicken feces could
be considered female-targeted baits. The problem
with such an interpretation is that the proportion of
males and females in the Þeld were not determined
and this leaves the possibility open to the fact that
more females than males were present at the moment
the study was conducted. But despite the fact that we
acknowledge the latter to be a possibility, unrelated
work by one of us (MA) in which thousands of pupae
were collected from Þeld-infested fruit in two differ-
ent localities (Veracruz and Chiapas, Mexico) re-
vealed that the proportion of Anastrepha females and
males emerging from such puparia was consistently
close to 50:50% (M. Aluja, unpub. data). Furthermore,
recent work by Robacker (1999) and Pin˜ero et al.
(2002), in which female/male proportion was con-
trolled during experiments, reveal that baits such as
BioLure, or Captor Plus (hydrolyzed protein), are
indeed more attractive to females than males.
The decrease we found in A. obliqua and A. serpen-
tina captures associated with the age of the torula
yeast/borax solution had been observed previously by
Epsky et al. (1994) with A. suspensa. These authors,
also working with torula, found that the attractiveness
of this bait decreased signiÞcantly as the lure aged.
First, we thought that this result could be attributed to
bait pH, as found by Bateman and Morton (1981)
when evaluating ammonium bicarbonate with Bactro-
cera tryoni (Froggatt) and by Robacker et al. (1993),
Robacker and Flath (1995), and Robacker and Bartlet
(1997) when testing bacteria Þltrates or cultures with
A. ludens and other Anastrepha species. But, contrary
to our expectation, our results indicate that the aging
process of baits did not affect signiÞcantly their pH
values and therefore, other factors mustbe inßuencing
differences in attractiveness.
Considering the combined results of studies 1 and 2,
there seems to be an indication of a species-speciÞc
response to certain baits. Aluja (1999) and Aluja et al.
(1989, 2001) addressed the possibility that not all of
the adults of various Anastrepha species respond with
equal intensity to a particular bait. Such differences
may be due, in part, to different nutritional require-
ments of adults. Pin˜ero et al. (2002) found that, under
laboratory conditions, adults of four Anastrepha spe-
cies showed differentialresponses to human urine and
hydrolyzed protein, and that at the individual level,
responses were signiÞcantly affected by the physio-
logical state (e.g., feeding history and age) of the
adults. For example, responses toward protein baits
decreased when adults had fed on an open fruit (an
important source of protein according to Ja´come et al.
1999). It has also been demonstrated that, even within
species, different responses to closely related volatiles
can be found. For example, Robacker and WarÞeld
(1993) reported that A. ludens adults responded dif-
ferently to ammonia and methylamine which share
some chemical properties. Likewise, Prokopy et al.
(1993) found different responses of C. capitata adults
to bird feces and mammal droppings, probably a result
of the type of volatiles emitted by such droppings,
because uric acid is one of the main products of bird
catabolism and urea is one of the most important
excretory products of mammal catabolism (Prosser
1991). The latter also could explain, in part, the higher
attraction of A. serpentina adults to bird feces com-
pared with human urine, though the same might not
be true for A. obliqua.
In conclusion, our Þndings herein, combined with
those of Hedstro¨m (1988), Epsky et al. (1997), and
Pin˜ero et al. (2002) indicate that human urine and
chicken feces are indeed attractive to Anastrepha
adults. Although in this study traps baited with human
urine and chicken feces captured fewer A. obliqua and
A. serpentina adults than traps baited with hydrolyzed
protein and torula yeast/borax,these inexpensive, nat-
urally occurring substances seem to have some posi-
tive attributes. In a relatively short period (#90 d),
inefÞcienttraps such as the McPhail, baited with these
compounds, captured 779 females. For a poor farmer,
who is accustomed to losing all or a large proportion
of their crop because of fruit ßy damage, it would be
advantageous to have fewer ovipositing females in a
population. Also, being able to gauge population num-
bers and the time at which adult ßies move into the
orchard from surrounding native vegetation will allow
a grower to strategically time cultural practices such
as fruit bagging (Fang 1989). A poor farmer could have
access to a cost-free trap by simply reusing a 2-liter
plastic bottle of a soft drink (Salles 1996) with the
appropriate dilution of human urine or chicken or
duck feces (Robacker et al. 2000). When judging the
potential of human urine and chicken feces as fruit ßy
baits we should keep in mind that the end goal of this
type of research is to develop low-technology baited
traps for resource-poor farmers who are not able to
338 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 96, no. 2
monitor ßy populations because commercially avail-
able baits and traps are too expensive. If inexpensive
or cost-free alternative baits and traps end up not
being as effective as the commercially available ones,
they could still be very useful for millions of small-
scale fruit growers in Latin America.
We thank Vicente Herna´ndez-Ortõ´z for help during the
identiÞcation process of Anastrepha adults. We alsothank the
technical supportprovidedby Isabel Ja´come, Enrique Piedra,
and Alberto Zu´n˜iga. We express gratitude to Nancy Epsky
(USDA-ARS),Ronald J. Prokopy,Juan Rull-Gabayet, Starker
Wright, Sara Hoffmann (University of Massachusetts, Am-
herst), and Francisco Dõ´az-Flesicher and Diana Pe´rez-Sta-
ples (Instituto de Ecologõ´a, A.C.) for reviewing an early
version of thismanuscript. Financialsupport wasprovidedby
the Secretary of Public Education (SEP) (Reg. DGICSA-
913096), the National Council for Science and Technology
(CONACyT)(Reg. 0702-N9109),and the Campan˜a Nacional
Contra Moscas de la Fruta (Agreement SAGARPA-IICA).
We thank the United States Department of Agriculture
(USDA-ARS-PPQ, facilities in Mexico City), for providing
torula yeast/borax pellets.
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Received for publication 5 April 2002; accepted 7 October
340 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 96, no. 2