Journal of Chemical Ecology, Vol. 15, No. 1, 1989
FLIGHT RESPONSE OF Heliothis subflexa (GN.) FEMALES (LEPIDOPTERA: NOCTUIDAE) TO AN ATTRACTANT FROM GROUNDCHERRY, Physalis
angulata L. 1
F.C.
TINGLE,
R.R.
HEATH,
and E.R.
MITCHELL
Insect Attractants, Behavior, and Basic Biology Research Laboratory Agricultural Research Service, U.S. Department of Agriculture Gainesville, Florida 32604 (Received August 11, 1987; accepted November 10, 1987)
Abstract--Mated female He6othis subflexa (Gn.) (HS) moths 1-7 days old responded positively in a Plexiglas flight tunnel to an attractant extracted with methanol from fresh whole-leaf washes of groundcherry, Physalis angulata L. Response to the groundcherry extract, as indicated by plume-tracking (i.e., upwind flight toward the odor source) and contact with the chemical dispenser did not change significantly during the first 5 hr of scotophase. Overall, ca. 50% of the responding moths also landed on the chemical dispenser; ca. 50% of the moths that landed also deposited eggs. There were no significant differences in the behavioral responses of females mating only once and those that had mated two or more times. Virgin females and male moths were significantly less responsive to the groundcherry attractant than mated females. The flight tunnel bioassay described provides an excellent system for evaluating plant allelochemics associated with host-plant selection. Key Words--Heliothis subflexa, Lepidoptera, Noctuidae, attractant, kairomone, groundcherry, Physalis angulatus, flight tunnel bioassay, plant-insect interaction.
INTRODUCTION
Environmentally controlled systems are needed to study host-finding behaviors of phytophagous insect species. The present study was designed to develop a ~This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or the recommendation for its use by USDA. 221
222
TINGLE ET AL.
system that could be used to evaluate host-plant attractants and associated behaviors (e.g., oviposition) in a controlled environment. Heliothis subflexa (Gn.) (HS) was selected as the test subject because of its limited host range (Physalis spp.) (Brazzel et al., 1953) and also because of potential changes in plant selection behaviors that might occur as a result of hybridization between HS and its sibling species H. virescens (F.) (HV) (Laster, 1972). Little is known about the nature o f flight responses of Heliothis moths to host-plant chemical stimuli.
METHODS AND MATERIALS
A Plexiglass flight tunnel was used to observe the behavior of HS to crude plant extract (Mitchell and Heath, 1987) obtained by washing fresh, whole groundcherry leaves in methanol. Typically, 100 g of groundcherry leaves were extracted for 30 sec in 500 ml of methanol. The extract was filtered and concentrated to 1 g/l ml with a rotary evaporator. The 60 x 60 x 185-cm tunnel was located in an environmentally controlled room 3 x 2.6 x 2.1 m. The room was maintained at ca. 26.8°C with a heat pump/air conditioner and ca. 50% relative humidity with a room humidifier. Overhead fluorescent lights (two banks of two 40-W bulbs) connected to an electric timer were used to control the reversed light-dark cycle (14 hr light; 10 hr dark). Three 25-W red light bulbs were spaced equally above the tunnel and remained on continuously. Air was pulled through the tunnel at 0.5 m/sec and was exhausted via a 30-cm-diam. flexible pipe with a fan. An intake vent located in the wall of the environmental chamber allowed a continuous flow of fresh air into the room from the outside. The HS used in the tests were obtained from our laboratory colony, which was started from ca. 300 larvae collected from groundcherry in the fall of 1983 and has had new genetic material introduced each fall since 1984 (Mitchell et al., unpublished data). The larvae were reared on a modified pinto bean diet (Guy et al., 1985). The insects were sexed in the pupal stage and separated before emergence of adults. Upon emergence, the adults were confined either in 3.8-liter cages as virgins or combined for mating (21 females and 14 males/ cage) and held until the desired age for testing. Insects were held under the same environmental conditions as were maintained in the flight tunnel room. On the day of testing, the moths were sexed by gently squeezing the abdomen to extrude the genitalia and the females were placed in a 25 x 25 x 50-cm Plexiglas holding cage, which was placed in the flight tunnel room ca. 1 hr before scotophase. Each test was begun by introducing l-g equivalent of groundcherry-methanol extract into the tunnel on the evaporator substrate (white muslin) placed over the end of a glass cylinder dispenser with a 3.5-cm opening. Air was blown
FLIGHT RESPONSE OF
Heliothis
223
through the cylinder and cloth into the tunnel with an aquarium pump at a rate of 1 liter/min to provide a continuous flow (plume) of the extract odor through the tunnel. The location of the plume through the center of the tunnel was verified previously by observing a smoke trail, produced by introducing smoke into the dispenser system. Each moth was removed individually from the holding cage and placed into a cylindrical 4 x 6.5-cm plastic release cage with screened ends. After placement of the release cage into the downwind end of the flight tunnel, the moth was released immediately and observed for 2 min. Behavioral responses were timed and recorded. All female moths were dissected after testing to confirm mating status. Tests with untreated controls were conducted periodically to ensure that response to the dispenser substrate (white muslin) was negligible when treated with solvent (methanol) only and that contamination of the bioassay system had not occurred. Data were analyzed by ANOVA or the unpaired t test (Steel and Torrie, 1960). Experiment 1. Females 1, 2, 3, 4, 5, 6, or 7 days old, which had been confined with males for mating, were tested to determine the effects of moth age on response to the groundcherry extract. Tests were conducted 1-4 hr after the beginning of scotophase. Specific responses, including flight initiation, type of flight (either undirected or plume tracking, i.e., following the plume trail upwind), contact with or without landing on the extract-treated substrate (white muslin), and duration (in sec) of each response were recorded. Three replications of 10 individuals each were completed for each age group. Experiment 2. A second experiment was conducted to determine if response to the extract changed significantly as the scotophase progressed. Mated female moths 3-6 days old were tested in the flight tunnel as described for the first experiment. The tests began ca. 10 min after the onset of scotophase and continued through the 5th hr of darkness. Data were tabulated from two replications of 37 individuals each for each hour. Experiment 3. In the third experiment, 3- to 5-day-old mated HS female moths were tested for their response to groundcherry extract in the flight tunnel as described previously. Special attention was focused on detecting any previously unobserved differences in the behavior of insects in the different response groups; i.e., (1) those that flew at random (undirected flight), (2) those that responded by tracking the plume trail from the extract dispenser, (3) those that made very brief contact with the extract-treated substrate but did not land, and (4) those that actually landed on the dispenser substrate. The time (sec) that each moth in each response group remained in the release cage before taking flight, the time spent in undirected flight, the number and duration (sec) of plume trackings, and when contacts and landings occurred also were recorded. Data collected from 3- to 5-day-old moths in experiments 1 and 2 were combined with the experiment 3 data to provide three replications of 150-170 individuals each.
224
TINGLE ET AL.
Since all of the HS females used in the various experiments were dissected to determine mating status, the data were tabulated to determine if the number of matings per female had any effect on moth response to the attractant. The number of matings per female was determined by the number of spermatophores counted in each moth upon dissection. Also, in experiment 3, the response of virgin HS females and males (0, 2, or 4 days old) to the groundcherry extract was determined during the first 3 hr of scotophase (three replications) using the criteria and methods described previously.
RESULTS AND DISCUSSION
Mated female HS moths in all age groups (experiment 1) demonstrated a positive anemotactic response to groundcherry extract (Figure 1). There were no significant differences in total response (59-71%) among the age groups (17 days old) (Figure 2). An average of 71% (1 day old), and 79% (7 days old) to 100% (4 days old) of the moths that followed the attractant plume also made contact or landed. Of these, 20% (7 days old) and 25% (1 day old) to 55% (4 days old) and 61% (3 days old) landed on the treated surface. There was a significant correlation (P < 0.05, r = 0.821, 5 df) between moth age and the percentage of moths that contacted the groundcherry extract without landing on the treated substrate. Seven-day-old moths made the most contacts (46%) but bad the fewest landings (13 %) (Figure 2). There were no significant differences among the age groups in the mean number of contacts (1-3) per female before landing on the extract-treated substrate or in the number of repeated contacts (1.5-4.8, including initial contact) when making contact without landing (Table 1). Also, moth age had no significant effect on (1) mean number of times a moth flew up the plume before landing, (2) number of times that an individual flew up the plume and made contact without landing, or (3) the number of plume trackings (1-2) by moths that responded without contacting the dispensing substrate (Table 1). Response to groundcherry extract by mated HS female moths (experiment 2) did not change significantly from 10 min to 5 hr after the initiation of darkness. The percent that either tracked the plume, contacted, or landed on the extract-treated substrate ranged from 84% during the first hour and 75-77% from hours 2-4, to 58% for those flown 4-5 hr after dark. In experiment 3, 73 % of the mated female HS moths responded to groundcherry extract by flying up the plume, contacting the dispenser, or landing (Table 2). There were no significant differences in the seconds before flight initiation (8.3-13.2) among the moths that did not respond to the extract and those that demonstrated a positive response. Although the resting position was sometimes
FIG. 1. Flight sequence of Heliothis subflexa in a positive anemotactic response to l-g equivalent of methanol extract from whole-leaf washes of fresh groundcherry leaves in methanol. Response includes plume tracking (1-3), contact with the extract-treated substrate (4), and landing (5-6) with possible oviposition.
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226
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2
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Contact but no londing
Plumeonlg 5
8
7
FIGE (OFIYS)
FIG. 2. R e s p o n s e in a flight tunnel o f m a t e d Heliothis subflexa f e m a l e s o f indicated age to l - g e q u i v a l e n t o f an attractant extracted by w a s h i n g fresh g r o u n d c h e r r y leaves in m e t h a n o l . Total r e s p o n s e includes flying up the o d o r p l u m e with no contact with the d i s p e n s e r , contacts without l a n d i n g , and l a n d i n g s .
TABLE 1. FREQUENCY OF BEHAVIORAL RESPONSES EXHIBITED BY INDIVIDUAL, MATED Heliothis subflexa FEMALE MOTHS OF INDICATED AGE TO I-GRAM EQUIVALENT OF ATTRACTANT FROM GROUNDCHERRY LEAVES DISPENSED DURING 120-SEC TESTS IN FLIGHT TUNNEL
Mean (+SE) No. contacts w/dispenser Moth age (days)
Before landing"
1
1.0 + 0.0
2 3 4 5 6 7
2.3 3.0 2.0 1.7 1.2 2.7
___ 0.2 + 0.6 5- 0.5 5- 0.4 5- 0.2 5- 0.0
Includes landing contact.
No landing 2.2 2.1 4.8 1.5 2.7 2,7 2.8
+ + + 5+ 55-
0.9 0.2 1.1 0.3 0.5 0.3 0.5
Mean (+SE) No. plume trackings Before landing 2.5 1.3 1.3 1.4 1.1 1.1 1.3
+ + + + + ± +
1.5 0.1 0.2 0.2 0.1 0.1 0.0
No landing 1.6 1.4 1.7 1.5 1.5 3.1 2.1
+ 0.3 + 0.2 + 0.4 + 0.3 + 0.2 5- 0.8 + 0.2
No contact or landing 1.3 + 0.3 1.9 + 0.1 1.9 + 0.6 1.0 5- 0.0 2.0 5- 0.0 1.5 5:0.3
FLIGHT RESPONSE OF Heliothis
227
TABLE 2. FUGHT DATA MEANS OF 3- TO 6-DAY-OLD, MATEDHeliothis subflexa FEMALE MOTHS RESPONDING TO 1-GRAM EQUIVALENT OF ATTRACTANT FROM GROUNDCHERRY LEAVES DISPENSED DURING 120-SEC TESTS IN FLIGHT TUNNEL
Behavioral response exhibited by moths (+SE) Contact with dispenser Flight data
Seconds before flight initiation Number of plume trackings Duration of plume trackings (sec) Number of contacts with dispenser Total flight time (sec)I'
None (27%)
Plume tracking (19%)
Did not land (17%)
Landed (37%)
13.2 + 1.7
8.3 _ 1.1
8.8 + 3.1
11.3 4- 1.0
0
1.7 + 0.1
1.9 + 0.1
1.1 + 0.0"
--
3.6 + 0.2
4.1 _+ 0.9
0
0.0
80.7 + 9.2
101.4 + 3.3
3.9:1:0.5
1.9 + 0.3
1.8 +_ 0.2"
107.1 5:3.1
38.5 + 3.3°
"Flight test terminated upon landing of moth on attractant dispenser. 1'Moths were in resting state for balance of 120-see test. assumed on the sides o f the tunnel during each 120-sec test, the total flying times (80.7-107.1 sec) of females that flew randomly, flew up the plume, or contacted and did not land on the substrate were significantly longer than the 38.5 (X) sec flown before landing by those that did land (F = 36.25, d f = 8, P < 0.0001, A N O V A ) . Upon landing, ca. 50% o f the moths landing were observed to oviposit on the dispenser before they could be captured and removed from the tunnel (Figure 1). However, detailed ovipositional behavior after landing was not studied in this experiment. The HS females that landed on the extract-treated substrate in experiment 3 (Table 2) made significantly fewer flights upwind toward the source o f the plume before landing than moths that responded to groundcherry extract by contacting or only following the plume (F = 27.22, 6 df, P < 0.001, A N O V A ) . However, the mean duration o f the plume trackings was statistically equal among moths that landed, contacted, or plume tracked only. The mean number of contacts (1.9) by moths that made contact but did not land was almost the same as the number o f contacts (1.8) made before and at time of landing by those that did land. The data obtained from the 4-day-old moths (N = 158) in experiment 3 are presented in Figure 3 to illustrate the typical flight behavior o f the mated females in response to groundcherry extract. Most (96%) o f the HS females
228
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FLIGHT RESPONSE OF Heliothis subflexa (GN.) FEMALES (LEPIDOPTERA: NOCTUIDAE) TO AN ATTRACTANT FROM GROUNDCHERRY, Physalis
angulata L. 1
F.C.
TINGLE,
R.R.
HEATH,
and E.R.
MITCHELL
Insect Attractants, Behavior, and Basic Biology Research Laboratory Agricultural Research Service, U.S. Department of Agriculture Gainesville, Florida 32604 (Received August 11, 1987; accepted November 10, 1987)
Abstract--Mated female He6othis subflexa (Gn.) (HS) moths 1-7 days old responded positively in a Plexiglas flight tunnel to an attractant extracted with methanol from fresh whole-leaf washes of groundcherry, Physalis angulata L. Response to the groundcherry extract, as indicated by plume-tracking (i.e., upwind flight toward the odor source) and contact with the chemical dispenser did not change significantly during the first 5 hr of scotophase. Overall, ca. 50% of the responding moths also landed on the chemical dispenser; ca. 50% of the moths that landed also deposited eggs. There were no significant differences in the behavioral responses of females mating only once and those that had mated two or more times. Virgin females and male moths were significantly less responsive to the groundcherry attractant than mated females. The flight tunnel bioassay described provides an excellent system for evaluating plant allelochemics associated with host-plant selection. Key Words--Heliothis subflexa, Lepidoptera, Noctuidae, attractant, kairomone, groundcherry, Physalis angulatus, flight tunnel bioassay, plant-insect interaction.
INTRODUCTION
Environmentally controlled systems are needed to study host-finding behaviors of phytophagous insect species. The present study was designed to develop a ~This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or the recommendation for its use by USDA. 221
222
TINGLE ET AL.
system that could be used to evaluate host-plant attractants and associated behaviors (e.g., oviposition) in a controlled environment. Heliothis subflexa (Gn.) (HS) was selected as the test subject because of its limited host range (Physalis spp.) (Brazzel et al., 1953) and also because of potential changes in plant selection behaviors that might occur as a result of hybridization between HS and its sibling species H. virescens (F.) (HV) (Laster, 1972). Little is known about the nature o f flight responses of Heliothis moths to host-plant chemical stimuli.
METHODS AND MATERIALS
A Plexiglass flight tunnel was used to observe the behavior of HS to crude plant extract (Mitchell and Heath, 1987) obtained by washing fresh, whole groundcherry leaves in methanol. Typically, 100 g of groundcherry leaves were extracted for 30 sec in 500 ml of methanol. The extract was filtered and concentrated to 1 g/l ml with a rotary evaporator. The 60 x 60 x 185-cm tunnel was located in an environmentally controlled room 3 x 2.6 x 2.1 m. The room was maintained at ca. 26.8°C with a heat pump/air conditioner and ca. 50% relative humidity with a room humidifier. Overhead fluorescent lights (two banks of two 40-W bulbs) connected to an electric timer were used to control the reversed light-dark cycle (14 hr light; 10 hr dark). Three 25-W red light bulbs were spaced equally above the tunnel and remained on continuously. Air was pulled through the tunnel at 0.5 m/sec and was exhausted via a 30-cm-diam. flexible pipe with a fan. An intake vent located in the wall of the environmental chamber allowed a continuous flow of fresh air into the room from the outside. The HS used in the tests were obtained from our laboratory colony, which was started from ca. 300 larvae collected from groundcherry in the fall of 1983 and has had new genetic material introduced each fall since 1984 (Mitchell et al., unpublished data). The larvae were reared on a modified pinto bean diet (Guy et al., 1985). The insects were sexed in the pupal stage and separated before emergence of adults. Upon emergence, the adults were confined either in 3.8-liter cages as virgins or combined for mating (21 females and 14 males/ cage) and held until the desired age for testing. Insects were held under the same environmental conditions as were maintained in the flight tunnel room. On the day of testing, the moths were sexed by gently squeezing the abdomen to extrude the genitalia and the females were placed in a 25 x 25 x 50-cm Plexiglas holding cage, which was placed in the flight tunnel room ca. 1 hr before scotophase. Each test was begun by introducing l-g equivalent of groundcherry-methanol extract into the tunnel on the evaporator substrate (white muslin) placed over the end of a glass cylinder dispenser with a 3.5-cm opening. Air was blown
FLIGHT RESPONSE OF
Heliothis
223
through the cylinder and cloth into the tunnel with an aquarium pump at a rate of 1 liter/min to provide a continuous flow (plume) of the extract odor through the tunnel. The location of the plume through the center of the tunnel was verified previously by observing a smoke trail, produced by introducing smoke into the dispenser system. Each moth was removed individually from the holding cage and placed into a cylindrical 4 x 6.5-cm plastic release cage with screened ends. After placement of the release cage into the downwind end of the flight tunnel, the moth was released immediately and observed for 2 min. Behavioral responses were timed and recorded. All female moths were dissected after testing to confirm mating status. Tests with untreated controls were conducted periodically to ensure that response to the dispenser substrate (white muslin) was negligible when treated with solvent (methanol) only and that contamination of the bioassay system had not occurred. Data were analyzed by ANOVA or the unpaired t test (Steel and Torrie, 1960). Experiment 1. Females 1, 2, 3, 4, 5, 6, or 7 days old, which had been confined with males for mating, were tested to determine the effects of moth age on response to the groundcherry extract. Tests were conducted 1-4 hr after the beginning of scotophase. Specific responses, including flight initiation, type of flight (either undirected or plume tracking, i.e., following the plume trail upwind), contact with or without landing on the extract-treated substrate (white muslin), and duration (in sec) of each response were recorded. Three replications of 10 individuals each were completed for each age group. Experiment 2. A second experiment was conducted to determine if response to the extract changed significantly as the scotophase progressed. Mated female moths 3-6 days old were tested in the flight tunnel as described for the first experiment. The tests began ca. 10 min after the onset of scotophase and continued through the 5th hr of darkness. Data were tabulated from two replications of 37 individuals each for each hour. Experiment 3. In the third experiment, 3- to 5-day-old mated HS female moths were tested for their response to groundcherry extract in the flight tunnel as described previously. Special attention was focused on detecting any previously unobserved differences in the behavior of insects in the different response groups; i.e., (1) those that flew at random (undirected flight), (2) those that responded by tracking the plume trail from the extract dispenser, (3) those that made very brief contact with the extract-treated substrate but did not land, and (4) those that actually landed on the dispenser substrate. The time (sec) that each moth in each response group remained in the release cage before taking flight, the time spent in undirected flight, the number and duration (sec) of plume trackings, and when contacts and landings occurred also were recorded. Data collected from 3- to 5-day-old moths in experiments 1 and 2 were combined with the experiment 3 data to provide three replications of 150-170 individuals each.
224
TINGLE ET AL.
Since all of the HS females used in the various experiments were dissected to determine mating status, the data were tabulated to determine if the number of matings per female had any effect on moth response to the attractant. The number of matings per female was determined by the number of spermatophores counted in each moth upon dissection. Also, in experiment 3, the response of virgin HS females and males (0, 2, or 4 days old) to the groundcherry extract was determined during the first 3 hr of scotophase (three replications) using the criteria and methods described previously.
RESULTS AND DISCUSSION
Mated female HS moths in all age groups (experiment 1) demonstrated a positive anemotactic response to groundcherry extract (Figure 1). There were no significant differences in total response (59-71%) among the age groups (17 days old) (Figure 2). An average of 71% (1 day old), and 79% (7 days old) to 100% (4 days old) of the moths that followed the attractant plume also made contact or landed. Of these, 20% (7 days old) and 25% (1 day old) to 55% (4 days old) and 61% (3 days old) landed on the treated surface. There was a significant correlation (P < 0.05, r = 0.821, 5 df) between moth age and the percentage of moths that contacted the groundcherry extract without landing on the treated substrate. Seven-day-old moths made the most contacts (46%) but bad the fewest landings (13 %) (Figure 2). There were no significant differences among the age groups in the mean number of contacts (1-3) per female before landing on the extract-treated substrate or in the number of repeated contacts (1.5-4.8, including initial contact) when making contact without landing (Table 1). Also, moth age had no significant effect on (1) mean number of times a moth flew up the plume before landing, (2) number of times that an individual flew up the plume and made contact without landing, or (3) the number of plume trackings (1-2) by moths that responded without contacting the dispensing substrate (Table 1). Response to groundcherry extract by mated HS female moths (experiment 2) did not change significantly from 10 min to 5 hr after the initiation of darkness. The percent that either tracked the plume, contacted, or landed on the extract-treated substrate ranged from 84% during the first hour and 75-77% from hours 2-4, to 58% for those flown 4-5 hr after dark. In experiment 3, 73 % of the mated female HS moths responded to groundcherry extract by flying up the plume, contacting the dispenser, or landing (Table 2). There were no significant differences in the seconds before flight initiation (8.3-13.2) among the moths that did not respond to the extract and those that demonstrated a positive response. Although the resting position was sometimes
FIG. 1. Flight sequence of Heliothis subflexa in a positive anemotactic response to l-g equivalent of methanol extract from whole-leaf washes of fresh groundcherry leaves in methanol. Response includes plume tracking (1-3), contact with the extract-treated substrate (4), and landing (5-6) with possible oviposition.
t,~
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r
226
TINGLE ET AL. B0
t7o 0 ._t~
o~_ o~ t3 1o
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tal ~8~p0~88
l
/r" / e
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2
3
~
/ 4
Contact but no londing
Plumeonlg 5
8
7
FIGE (OFIYS)
FIG. 2. R e s p o n s e in a flight tunnel o f m a t e d Heliothis subflexa f e m a l e s o f indicated age to l - g e q u i v a l e n t o f an attractant extracted by w a s h i n g fresh g r o u n d c h e r r y leaves in m e t h a n o l . Total r e s p o n s e includes flying up the o d o r p l u m e with no contact with the d i s p e n s e r , contacts without l a n d i n g , and l a n d i n g s .
TABLE 1. FREQUENCY OF BEHAVIORAL RESPONSES EXHIBITED BY INDIVIDUAL, MATED Heliothis subflexa FEMALE MOTHS OF INDICATED AGE TO I-GRAM EQUIVALENT OF ATTRACTANT FROM GROUNDCHERRY LEAVES DISPENSED DURING 120-SEC TESTS IN FLIGHT TUNNEL
Mean (+SE) No. contacts w/dispenser Moth age (days)
Before landing"
1
1.0 + 0.0
2 3 4 5 6 7
2.3 3.0 2.0 1.7 1.2 2.7
___ 0.2 + 0.6 5- 0.5 5- 0.4 5- 0.2 5- 0.0
Includes landing contact.
No landing 2.2 2.1 4.8 1.5 2.7 2,7 2.8
+ + + 5+ 55-
0.9 0.2 1.1 0.3 0.5 0.3 0.5
Mean (+SE) No. plume trackings Before landing 2.5 1.3 1.3 1.4 1.1 1.1 1.3
+ + + + + ± +
1.5 0.1 0.2 0.2 0.1 0.1 0.0
No landing 1.6 1.4 1.7 1.5 1.5 3.1 2.1
+ 0.3 + 0.2 + 0.4 + 0.3 + 0.2 5- 0.8 + 0.2
No contact or landing 1.3 + 0.3 1.9 + 0.1 1.9 + 0.6 1.0 5- 0.0 2.0 5- 0.0 1.5 5:0.3
FLIGHT RESPONSE OF Heliothis
227
TABLE 2. FUGHT DATA MEANS OF 3- TO 6-DAY-OLD, MATEDHeliothis subflexa FEMALE MOTHS RESPONDING TO 1-GRAM EQUIVALENT OF ATTRACTANT FROM GROUNDCHERRY LEAVES DISPENSED DURING 120-SEC TESTS IN FLIGHT TUNNEL
Behavioral response exhibited by moths (+SE) Contact with dispenser Flight data
Seconds before flight initiation Number of plume trackings Duration of plume trackings (sec) Number of contacts with dispenser Total flight time (sec)I'
None (27%)
Plume tracking (19%)
Did not land (17%)
Landed (37%)
13.2 + 1.7
8.3 _ 1.1
8.8 + 3.1
11.3 4- 1.0
0
1.7 + 0.1
1.9 + 0.1
1.1 + 0.0"
--
3.6 + 0.2
4.1 _+ 0.9
0
0.0
80.7 + 9.2
101.4 + 3.3
3.9:1:0.5
1.9 + 0.3
1.8 +_ 0.2"
107.1 5:3.1
38.5 + 3.3°
"Flight test terminated upon landing of moth on attractant dispenser. 1'Moths were in resting state for balance of 120-see test. assumed on the sides o f the tunnel during each 120-sec test, the total flying times (80.7-107.1 sec) of females that flew randomly, flew up the plume, or contacted and did not land on the substrate were significantly longer than the 38.5 (X) sec flown before landing by those that did land (F = 36.25, d f = 8, P < 0.0001, A N O V A ) . Upon landing, ca. 50% o f the moths landing were observed to oviposit on the dispenser before they could be captured and removed from the tunnel (Figure 1). However, detailed ovipositional behavior after landing was not studied in this experiment. The HS females that landed on the extract-treated substrate in experiment 3 (Table 2) made significantly fewer flights upwind toward the source o f the plume before landing than moths that responded to groundcherry extract by contacting or only following the plume (F = 27.22, 6 df, P < 0.001, A N O V A ) . However, the mean duration o f the plume trackings was statistically equal among moths that landed, contacted, or plume tracked only. The mean number of contacts (1.9) by moths that made contact but did not land was almost the same as the number o f contacts (1.8) made before and at time of landing by those that did land. The data obtained from the 4-day-old moths (N = 158) in experiment 3 are presented in Figure 3 to illustrate the typical flight behavior o f the mated females in response to groundcherry extract. Most (96%) o f the HS females
228
TINGLE ET AL.
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ACT,VAT,ON ~
96
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(repeat) 22
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