Airborne Pheromone Research Articles

Robotic communication with ants.

ABSTRACTWe used a robotic gantry to test the hypothesis that tandem running in the ant Temnothorax albipennis can be successful in the absence of trail laying by the leader. Pheromone glands were placed on a pin attached to a gantry. This set-up substituted for the leader of a tandem run. Neither the pin nor the glands touched the substrate and thus the ant following the robot was tracking a plume of airborne pheromones. The robot led individual workers from their current nest to a potential new one. The robotic gantry was programmed to allow for human intervention along its path to permit the following ant to stop and survey its surroundings and then catch up with its mechanical leader. The gantry then automatically tracked the precise route taken by each ant from the new nest back to the old one. Ants led by the robot were significantly more successful at finding their way home than those we carried to the new nest that had no opportunity to learn landmarks. The robot was programmed to take either a straight or a sinusoidal path to the new nest. However, we found no significant difference in the abilities of ants that had been led on such direct or sinuous paths to find their way home. Here, the robot laid no trail but our findings suggest that, under such circumstances, the following ant may lay a trail to substitute for the missing one.

Risky business: males choose more receptive adults over safer subadults in a cannibalistic spider.

Understanding factors affecting male mate choice can be important for tracking the dynamics of sexual selection in nature. Male brown widow spiders (Latrodectus geometricus) mate with adult as well as immature (subadult) females. Mating with adults involves costly courtship with a repertoire of signaling behaviors, and typically ends with cannibalism (“self-sacrifice” initiated by male somersault). Mating with subadults involves brief courtship with behavioral repertoire reduced to one component (vibration) and no cannibalism. We examined male mate choice as a function of risks associated with different types of mates and the cues available to courting males. Previous studies showed male preference for adults based on air-borne pheromones, but it was unclear whether that preference is maintained after males reach female’s webs. We show that males prefer adults also based on silk-borne contact cues. To determine which types of cues trigger different courtship components, we swapped adults and subadults between webs. We showed that contact with adult females’ webs triggers two courtship behaviors from the repertoire, with adult female’s bodies triggering additional behaviors. However, vibrational signals occur regardless of the web origin or female developmental stage. We conclude that males recognize subadult females as potential mates, but are more likely to invest in costly courtship behaviors and mating attempts with adults. In our experiments, subadults were less likely to mate than adults. We conclude that mating with adults could be the preferred option for males because of the higher likelihood of copulation, even at the cost of a higher risk of cannibalism.

Laboratory investigation of pheromone pre‐exposure in Lobesia botrana males indicates minor role of desensitization in the field

AbstractThe role of desensitization in mating disruption (MD) of European Grapevine Moth (EGVM), Lobesia botrana (Dennis and Schiffermüller) (Lepidoptera: Tortricidae), is studied by exposing males to different airborne pheromone concentrations for various time intervals prior to evaluate their behavioural response. By using different types of dispensers, male moths are exposed to three decreasing pheromone concentrations (up to the minimum concentration able to desensitize them) for 1, 3, and 24 h. The airborne pheromone concentration present in all treatments is accurately quantified using gas chromatography–mass spectrometry equipment to compare these data with actual airborne pheromone concentrations under field conditions. The effect of pheromone exposure on L. botrana males is studied in wind tunnel and electroantennogram assays, immediately and 24 h after the exposure period. Results show that the reduction of response to the pheromone depended on the dose and the duration of the treatment, but the lowest dose tested did not produce desensitization. These results support that the most important mechanisms of MD acting in fields treated against EGVM are the competitive ones and that the non‐competitive ones only may become relevant very close to pheromone dispensers. Our results support the hypothesis of cross‐adaptation to other chemical stimuli in the pre‐exposed moths to their pheromone although more studies are needed to draw stronger conclusions.

Airborne Pheromone Quantification in Treated Vineyards with Different Mating Disruption Dispensers against Lobesia botrana.

Mating disruption (MD) is widely used against the European grapevine moth (EGVM), Lobesia botrana (Denis and Schiffermüller; Lepidoptera: Tortricidae), by installing passive dispensers or aerosol devices. The present work reports a new sampling and quantification methodology to obtain absolute data about field airborne pheromone concentration based on air samplings and sensitive chromatographic-spectroscopic methods. Samplings were performed in fields treated with passive dispensers or aerosol devices at different moments throughout the crop cycle to study how they act and how the disruption is triggered. Moreover, pheromone adsorption and releasing capacity of vine leaves were studied to elucidate their role in the disruption. Although both types of dispensers were effective in limiting the damage inflicted by EGVM, they performed differently and provided different airborne pheromone concentration profiles. Results also proved that leaves were able to adsorb and release part of the airborne pheromone acting as subsequent and additional pheromone sources. This fact could explain the different concentration profiles. Moreover, our results suggest that lower pheromone emission than that of the current passive dispensers still could provide an adequate performance in the field. Competitive mechanisms involved in MD using both dispensers, the dynamics of the airborne pheromone throughout the time and the importance of the canopy are discussed.

Male responses suggest both evolutionary conservation and rapid change in chemical cues of female widow spiders

Understanding patterns of diversity in sexual signals can give insight into processes initiating, mediating or following from species diversification. Here we focus on female sex pheromones, which are widespread among animals, where some taxa show phylogenetic patterns of variation, but for others, ecological factors better explain pheromone diversity. Causes of differences in these patterns are unclear, and general insights require studying a broader range of taxa. Here we examined variation in the responses of male redback spiders, Latrodectus hasselti, to sex pheromones produced by three allopatric female congeners with different degrees of phylogenetic relatedness (from the same clade: Latrodectus mirabilis, Latrodectus hesperus; and from a different clade: Latrodectus geometricus) to infer pheromone divergence. We examined variation in male responses to conspecific and heterospecific females’ airborne and contact pheromones, which attract males and elicit courtship behaviour, respectively. We measured male courtship responses to extracted contact pheromones in isolation and male preferences in response to airborne pheromones and combined cues (pheromones, silk) in a two-choice maze. Male responses to airborne chemicals, contact chemicals and combined cues suggested variation in species specificity, with L. hasselti males showing strong discrimination against airborne pheromones of L. hesperus females (same clade), moderate evidence for discrimination based on contact cues of L. geometricus, but only when multiple sources of information were available (different clade), and no discrimination of L. mirabilis females (same clade) relative to conspecifics, regardless of the types of information available. Thus, male responses were not consistent with a phylogenetic pattern. Moreover, airborne pheromones can apparently diverge relatively rapidly, but airborne and contact pheromones may remain similar across long evolutionary timescales. We propose that differential responses to L. hesperus may arise from selection for population-level pheromone divergence within that species and that, in general, pheromones and male responses may be evolutionarily conserved across Latrodectus.

The role of silk in courtship and communication in mygalomorph spiders: Do males regulate their courtship in response to female mating status?

In spiders, pheromones are known to be responsible for attracting the opposite sex, eliciting male searching and courtship behaviors, as well as for synchronizing potential mates in space and time. Most spiders are cannibalistic and aggressive. Thus, early recognition of a female as a possible mate is essential for males, who may suffer high energetic or reproductive costs to the extreme of losing all fitness opportunities. In Acanthogonatus centralis Goloboff 1995, a mygalomorph spider, what female signs might be triggering male courtship behavior remain unknown, as well as whether males can discriminate between females. The aims of the present work were (1) establishing whether males can detect the presence of females using airborne and silk-borne signals and (2) determining whether males can discriminate the reproductive status and body condition of females. We found no evidence that airborne pheromones play a role in the sexual communication of A. centralis, but silk-bound contact signals function as a female advertisement. Also, this is the first study that demonstrates that male mygalomorph spiders can discriminate between different signals on silk through direct contact, showing a preference for unmated females.

Associative learning is necessary for airborne pheromones to activate sexual arousal-linked brain areas of female rats

In rodents, urine-borne male pheromones include volatile organic compounds (VOCs) and major urinary proteins (MUPs). In mice, the attraction of females to male odor is reportedly acquired through associative learning with MUPs in some studies. Here, we found that VOC and MUP sex pheromones were differentiated in rats at around 8 weeks of age and that females separated from males at weaning showed no preference for male urine odor after sexual maturity. Olfactory preferences could be gained in females after repeated experience of VOC pheromones alone as well as male urine or a blend of synthetic VOC pheromones and recombinant MUPs. However, differences in acquired olfactory preferences for male urine were further revealed by neuro-immuno-histochemical studies. The blend exhibited neural activation in the main olfactory system (MOS), accessory system (AOS), and the ventromedial hypothalamus (VMH), indicating sexual arousal, whereas the VOC alone only caused neural activation of MOS. We suggest that olfactory preference is generated through repeated experience of either VOCs or a blend of VOCs and MUPs, but the neural activations related to sexual arousal have to be acquired through associative learning with MUPs in female rats. When adult female rats were separated from males before maturity, they lost their attraction to male urine odor. Female preference to volatiles in male urine could be gained by repeated experience of volatile and protein pheromones. Brain regions related to sexual arousal were activated by male urine in females with experience of VOCs together with MUPs but not in those experienced with VOCs alone. Associative learning between VOC and MUP pheromones is necessary for male urine odor-induced FOS responses in the key regions for sexual arousal/excitement in female rats.

Comparative analysis of efficacy and longevity of various pheromone baited Septa for the control of gram pod borer

Pheromones are species specific chemicals which are biodegradable, eco-friendly, chemically safe, and required in ultra low dosages and used as efficient tool for insect pest management. Efficiency of pheromone traps used for pest control depends on air borne pheromone stimulus, in specific ratio and concentration released from septa. Field longevity of synthetic lures for Helicoverpa armigera (Lepidoptera: Noctudae) and efficacy of different septa were evaluated by mass trapping experiments in Pantnagar, India. The longevity (shelf life) of septa impregnated with pheromone components (Hexadecenol) and 97:3 blend (Z-11-hexadecenal and Z-9-Hexadecenal) were studied by gas chromatographic estimation of the residual pheromone remaining on the septa at different time interval and temperature conditions. The rubber eraser septum is found to be most effective one. This study is helpful to popularize the pheromone technology in farmers as they can store the already loaded septa and use them for control of H.armigera.

Investigation of two new putative pheromone components of the invasive Australian redback spider, Latrodectus hasseltii, with potential applications for control

ABSTRACTThe Australian redback spider, Latrodectus hasseltii preys on at least 10 endemic species in New Zealand, highlighting a need for control. Male redbacks are attracted to virgin females by an airborne pheromone. The aim of this study was to analyse the response of male redback spiders to two volatile chemicals found on the silk of virgin but not mated females, to determine whether these compounds constitute components of the airborne pheromone. Mature male redback spiders were placed in an olfactometer where they had a choice of two stimuli. We compared their response to paired combinations of a control, virgin silk, butyric acid and isovaleric acid. Male redbacks responded equally strongly to butyric acid and virgin silk, in terms of time spent near the stimulus. The identification of butyric acid as a component of the airborne sex pheromone of L. hasseltii provides the groundwork for developing a pheromone-based control.

Comparative analysis of efficacy and longevity of different pheromone baited septa for control of Gram Pod Borer in chickpea in Uttaranchal, India

Pheromones are species specific chemicals which are biodegradable, eco-friendly, chemically safe, and required in ultra low dosages and used as efficient tool for insect pest management. Efficiency of pheromone traps used for pest control depends on air borne pheromone stimulus, in specific ratio and concentration released from septa. Field longevity of synthetic lures for Helicoverpa armigera (Lepidoptera: Noctudae) and efficacy of different septa were evaluated by mass trapping experiments in Pantnagar, India.The longevity (shelf life) of septa impregnated with pheromone components (Hexadecenol) and 97:3 blend (Z-11-hexadecenal and Z-9-Hexadecenal) were studied by gas chromatographic estimation of the residual pheromone remaining on the septa at different time interval and temperature conditions. The rubber eraser septum is found to be most effective one. This study is helpful to popularize the pheromone technology among the farmers as they can store the already loaded septa and use them for control of H.armigera.

Mate-location flight of the red-necked longicorn beetle, Aromia bungii (Coleoptera: Cerambycidae): an invasive pest lethal to Rosaceae trees

The red-necked longicorn beetle, Aromia bungii (Faldermann) (Coleoptera: Cerambycidae), which has recently invaded Japan, is a serious pest species. The larvae kill cherry and orchard Rosaceae trees, such as peach, plum, and apricot. To clarify their features for mate location, male and female flight behaviors were observed in wind tunnels with caged males and females as lures. In a small wind tunnel (50 cm in diameter, 2 m in length), both sexes showed takeoff behavior according to increasing airflow. The rate of female takeoff against the male lure, a live male in a wire-netting cage, tended to be higher than for other combinations. In a large wind tunnel (ca. 1.6 m in diameter, 4 m in length), both sexes ascended and showed momentary hovering and astatic flight. When male lure cages were placed windward in the wind tunnel, females showed “upwind flight,” while males did not. It is assumed that females were induced to fly upwind by a factor derived from live males, likely to be an airborne pheromone component.

The smell of sex: water-borne and air-borne sex pheromones in the intertidal gastropod Littorina littorea

We investigated whether individuals of the intertidal snail Littorina littorea may be attracted by waterborne and air-borne pheromones from conspecifics. The potential relative role of water-borne and air-borne pheromone in the behavioural and reproductive biology of L. littorea was assessed through chemotactic assays. These involved a series of choice experiments with snails, snail smell and snail mucus as stimuli in a T-maze under conditions of immersion and emersion, and during the nonmating and mating seasons. During the nonmating season, L. littorea did not choose the snail-conditioned side of the T-maze significantly more frequently than the control side under conditions of both immersion and emersion. During the mating season, under condition of immersion both males and females chose the side of the T-maze conditioned with individual of the opposite sex significantly more frequently than the control side, and did not show any preference for the side conditioned with individuals of the same sex. Under conditions of emersion, only males were significantly more attracted by cues from the opposite sex than by the control. These results indicate that L. littorea are not attracted by conspecifics during the nonmating season; the cues of conspecifics are then unlikely to play a role in the orientation or the aggregation behaviour of this species. The results also suggest that males and females are attracted by the odour of conspecifics of the opposite sex, which contains both water-borne and air-borne pheromones in females and only water-borne pheromones in males. Also the similar behaviours observed with snails, water-borne and air-borne snail smell, and snail mucus, as stimuli indicate that male and female sex pheromones are both present in mucus. Temperature manipulations conducted during both seasons did not affect any of the observed behavioural changes, hence suggesting that the chemoreceptive abilities of L. littorea may be driven by exogenous and/or endogenous factors that are decoupled from direct control by temperature. This is in sharp contrast to the locomotor activity of L. littorea, which consistently increased with temperature. We also report the possibility of mate-tracking in females, a behaviour that has yet to be reported in gastropods, since males are typically believed to be the active sex that searches for females. Our results build on previous evidence of the function played by mucus-trail following in the reproductive success of intertidal gastropods, through the ability of L. littorea to remotely detect the water-borne and air-borne sex-specific cues that are incorporated in their mucus.

Strong, convergent male mate choice along two preference axes in field populations of black widow spiders

Strong male mate preferences have been documented in species with otherwise conventional sex roles in the laboratory, and across taxa, male preferences generally focus on indicators of female fecundity and sperm competition risk. However, the few field studies of male choice rarely show equally strong effects. This suggests that costs of choice in nature may make the expression of preferences unlikely, or that interacting assessment cues may lead to unpredictable and variable outcomes in the wild. Field studies are therefore critical for testing whether or not male mate choice is sufficiently strong to exert sexual selection on females. Here we examine male choice in nature in response to two experimentally manipulated cues of female reproductive value. We recorded the attraction of male black widow spiders, Latrodectus hesperus, to females in a field enclosure and in a unconstrained natural setting. Stimulus females varied in two ways: sperm competition risk (low–unmated; high–mated) and fecundity (high–fed; low–unfed). Females and their silk were caged to prevent behavioural interactions while allowing the spread of airborne pheromones that attract males. Males in both experiments showed strong, nearly unanimous choice for unmated, well-fed females. In field enclosures, 80% of males made this choice, and wild males made the same choice in 94% of trials. We conclude that male choice in L. hesperus is mediated by detection of airborne pheromones, is strong and consistent despite natural costs of mate searching, and is not affected by natural interactions between (sometimes conflicting) cues of female reproductive value. Thus, universal mate choice may exist among males in nature. We propose general features of systems in which this may be likely and discuss implications for the study of sexual selection on females under conventional sex roles.

A portable gas chromatograph with simultaneous detection by mass spectrometry and electroantennography for the highly sensitive in situ measurement of volatiles

Mating disruption is a sustainable method for the control of insect pests, involving the release of synthetic sex pheromones that disrupt the olfactory localization of females by males. However, the development and refinement of this strategy is hampered because current instruments lack the sensitivity to detect volatile organic chemicals in the field, and portable electroantennograms produce non-comparable relative units and distorted results in the presence of plant volatiles. To address the demand for more sensitive instruments that are suitable for the rapid in situ detection of airborne pheromones, we have developed a portable, automated needle trap device connected to a gas chromatograph, mass spectrometer, and electroantennographic detector (NTD-GC-MS/EAD) suitable for field applications. We tested the instrument by measuring the concentration of the sex pheromone (E,Z)-7,9-dodecadienyl acetate, which is used to disrupt the mating of the European grapevine moth Lobesia botrana (Lepidoptera: Tortricidae). Our data confirm that the instrument generates highly reproducible results and is highly sensitive, with a detection threshold of 3ng/m(3) (E,Z)-7,9-dodecadienyl acetate in outside air.

On-site airborne pheromone sensing

Pheromones and other semiochemicals play an important role in the natural world by influencing the behavior of plants, mammals, and insects. In the latter case, species-dependent pheromone communication has numerous applications, including the detection, trapping, monitoring and guiding of insects, as well as pest management in agriculture. On-site sensors are desirable when volatile organic compounds (VOCs) are used as semiochemicals. Insects have evolved highly selective sensors for such compounds, so biosensors comprising complete insects, isolated organs or individual proteins can be highly effective. However, isolated insect organs have a limited lifetime as biosensor, so biomimetic approaches are needed for prolonged monitoring, novel applications, or measurements in challenging environments. We discuss the development of on-site biosensors and biomimetic approaches for airborne-pheromone sensing, together with biomimetic VOC sensor systems. Furthermore, the infochemical effect describing the anthropogenic contamination of the ecosystem through semiochemicals, will be considered in the context of novel on-site pheromone sensing-systems.

Snails and their trails: the multiple functions of trail‐following in gastropods

Snails are highly unusual among multicellular animals in that they move on a layer of costly mucus, leaving behind a trail that can be followed and utilized for various purposes by themselves or by other animals. Here we review more than 40 years of experimental and theoretical research to try to understand the ecological and evolutionary rationales for trail-following in gastropods. Data from over 30 genera are currently available, representing a broad taxonomic range living in both aquatic and terrestrial environments. The emerging picture is that the production of mucus trails, which initially was an adaptation to facilitate locomotion and/or habitat extension, has evolved to facilitate a multitude of additional functions. Trail-following supports homing behaviours, and provides simple mechanisms for self-organisation in groups of snails, promoting aggregation and thus relieving desiccation and predation pressures. In gastropods that copulate, trail-following is an important component in mate-searching, either as an alternative, or in addition to the release of water- or air-borne pheromones. In some species, this includes a capacity of males not only to identify trails of conspecifics but also to discriminate between trails laid by females and males. Notably, trail discrimination seems important as a pre-zygotic barrier to mating in some snail species. As production of a mucus trail is the most costly component of snail locomotion, it is also tempting to speculate that evolution has given rise to various ways to compensate for energy losses. Some snails, for example, increase energy intake by eating particles attached to the mucus of trails that they follow, whereas others save energy through reducing the production of their own mucus by moving over previously laid mucus trails. Trail-following to locate a prey item or a mate is also a way to save energy. While the rationale for trail-following in many cases appears clear, the basic mechanisms of trail discrimination, including the mechanisms by which many snails determine the polarity of the trail, are yet to be experimentally determined. Given the multiple functions of trail-following we propose that future studies should adopt an integrated approach, taking into account the possibility of the simultaneous occurrence of many selectively advantageous roles of trail-following behaviour in gastropods. We also believe that future opportunities to link phenotypic and genotypic traits will make possible a new generation of research projects in which gastropod trail-following, its multitude of functions and evolutionary trade-offs can be further elucidated.

Female calling and male flight orientation and searching behaviors in Callisphyris apicicornis: evidence for a female-produced sex attractant pheromone

T. Curkovic, and C. Ferrera. 2012. Female calling and male flight orientation and searching behaviors in Callisphyris apicicornis: evidence for a female-produced sex attractant pheromone. Cien. Inv. Agr. 39(1): 147-158. Callisphyris apicicornis is a fruit pest of increasing concern in Chile. To aid in the identification of its sex pheromone for use in the management of this insect, “calling” (pheromone release) of females and “orientation and searching” behaviors of males to calling females were video recorded. Light intensity, wind speed, temperature, time of the day, and the frequency of individuals performing each step within both behavioral sequences were recorded as well. Drawings of the behavioral steps and ethograms (routes and returns) are also provided, including transition frequencies between behavioral steps. The calling behavior of females included diagnostic movements of the abdomen, legs, elytra, and wings, showing similarities to the descriptions of other cerambycid species in which females call. The orientation and searching behavior of males included zigzagging flights (characteristic steps observed in insects responding to airborne pheromone plumes) and landing on and searching for females in cages. Females called and males responded mainly between 9 AM and 1 PM. Both behaviors were performed in a non-random fashion and were stereotyped. Calling behavior was significantly affected by light (apparently triggering the behavior) but not by wind speed, ambient temperature, or female age. Males tended to respond most strongly to younger females, although these called significantly less frequently than older ones. These results strongly support the existence of a female-produced sex pheromone in C. apicicornis and provide the background information to aid in attempts of pheromone collection and identification. Male behavior characterization also provides a base-line to compare with tests to evaluate the activity of putative pheromones for this species. This study is one of the first reports of a cerambycid species in which the female calls and the male consequently responds to her and the first one on the characterization of the calling and oriented searching behaviors for a Necydalinae.

Life history parameters and scale‐cover surface area of Aonidiella aurantii are altered in a mating disruption environment: implications for biological control

In recent years, environmentally safe measures to control the California red scale (CRS), Aonidiella aurantii (Maskell), have been successfully implemented. These measures include mating disruption (MD) and biological control. The goal of this study was to examine the effect of high concentrations of the CRS sex pheromone on its life history parameters and scale-cover surface area under controlled laboratory conditions. The developmental time of both males and females of CRS increased with exposure to airborne pheromone. MD had an effect on both the total number of progeny and on the crawler production period for females. Accordingly, demographic parameters such as net fecundity (R(0) ) and intrinsic rate of increase (r(m) ) were significantly lower in the pheromone-treated populations. The largest scale-cover surface areas were observed in the CRS reared in the pheromone environment. A clear influence of airborne pheromone on the biology of CRS has been demonstrated. In addition to the classical mating disruption benefits of this technique, additional benefits, such as increase in the duration of exposure to natural enemies and increase in size, which benefits some species of parasitoids, have been confirmed.

Robot Pheromone Communication Using Vortex Ring Transmission

Unpredictable air movements have proved to be a problem in previous studies investigating robot communication by means of airborne pheromone chemicals. The project described in this paper investigates the use of air vortex rings as a means of carrying pheromone chemicals between transmitting and receiving robots. Sensitivity to chemicals including pheromones released by conspecifics is essential for many aspects of an insect's life. They assist in finding food, locating a mate, avoiding danger and help coordinate the activities of social insects. In the future, autonomous robots will be challenged by many situations similar to those that face insects and other simple creatures. Chemical communication may prove useful for these robots as well. This paper describes the equipment developed for generating and detecting vortex rings. Results of experiments involving location and tracking of a sequence of pheromone vortex rings are also presented.

Measurement by electroantennogram of airborne pheromone in cotton treated for mating disruption of Pectinophora gossypiella following removal of pheromone dispensers

AbstractThe presence of pheromone in cotton foliage after removal of pheromone dispensers was assessed by measuring the airborne pheromone concentration with an electroantennogram device. Plots of 0.4 ha in isolated cotton fields were treated with Shin‐Etsu PBW‐Rope® pheromone dispensers for mating disruption of Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae). The dispensers contained (Z,Z)‐ and (Z,E)‐7,11‐hexadecadienyl acetates (gossyplure) in a 49:51 ratio and were applied at a density of 1 000/ha. The 400 pheromone dispensers were removed 1–12 days later. In four experiments involving canopy heights from 30–150 cm, the decay of the pheromone concentration was recorded repeatedly in short intervals for up to 7 h. Decay to undetectable concentrations generally occurred within 1–10 h, depending on plant size and wind conditions. In all four experiments, pheromone concentration 24 h after removal was found to be near or below detection threshold of the electroantennogram. The presence of pheromone within and above the cotton after dispenser removal would be due to re‐entrainment of pheromone that had been adsorbed on cotton foliage or possibly some residual airborne pheromone.