Odor Plume Research Articles

High-Dimensional Time Series Feature Extraction for Low-Cost Machine Olfaction

The complexity of airborne odors offers interesting challenges and opportunities for chemical detection and identification. Biological olfactory systems have evolved to extract information from spatiotemporally complex odor plumes, but many engineered electronic noses use only coarse time features while neglecting valuable transient fluctuations. In this paper, we use the TruffleBot , our low-cost e-nose platform, to dynamically ‘sniff’ odors while collecting multidimensional chemical, pressure and temperature time series. By extracting high-dimensional time series features (TSF) from a diverse set of relatively low-bandwidth sensor signals, we can identify subtle differences in odor concentration and composition. We use this approach to perform a variety of classification experiments, including the discrimination of three similar beers at >98% accuracy. Additionally, we demonstrate that time series features can be aggregated and applied to improve concentration estimation of ethanol by a factor of three, to the limit of our experimental calibration error.

A Comparison between Mouse, In Silico, and Robot Odor Plume Navigation Reveals Advantages of Mouse Odor Tracking.

Localization of odors is essential to animal survival, and thus animals are adept at odor navigation. In natural conditions animals encounter odor sources in which odor is carried by air flow varying in complexity. We sought to identify potential minimalist strategies that can effectively be used for odor-based navigation and asses their performance in an increasingly chaotic environment. To do so, we compared mouse, in silico model, and Arduino-based robot odor-localization behavior in a standardized odor landscape. Mouse performance remains robust in the presence of increased complexity, showing a shift in strategy towards faster movement with increased environmental complexity. Implementing simple binaral and temporal models of tropotaxis and klinotaxis, an in silico model and Arduino robot, in the same environment as the mice, are equally successful in locating the odor source within a plume of low complexity. However, performance of these algorithms significantly drops when the chaotic nature of the plume is increased. Additionally, both algorithm-driven systems show more successful performance when using a strictly binaral model at a larger sensor separation distance and more successful performance when using a temporal and binaral model when using a smaller sensor separation distance. This suggests that with an increasingly chaotic odor environment, mice rely on complex strategies that allow for robust odor localization that cannot be resolved by minimal algorithms that display robust performance at low levels of complexity. Thus, highlighting that an animal's ability to modulate behavior with environmental complexity is beneficial for odor localization.

Modeling of H2S Dispersion in Brazil with Aermod: Case Study of Water Resource Recovery Facility In South of Brazil

Abstract Water Resource Recovery Facility (WRRF) can be source of odorous gases. We analyzed the emission and dispersion of hydrogen sulfide gas (H2S), odor indicator, produced during the anaerobic treatment of wastewaters, using WATER9 and AERMOD models for two distinct events: August 2013 and February-March 2014. Data from two WRRF in Brazil were used to feed the model and a statistical data validation was performed, followed by an evaluation of model results regarding H2S emission and dispersion. Daily peak events and averages over the two periods were calculated. Results show a good performance from the model in comparison to the observations. Moreover, odor plumes typically reached 2-4 km from their sources and they may be strongly affected by atmospheric stability/instability conditions in the events analyzed and, in general, only the residences at the vicinity of WRRF were affected by the pollutant odor. Finally, the methodology presented showed to be feasible and realistic for purposes of WRRF planning and management.

Odor Stimuli: Not Just Chemical Identity.

In most sensory modalities the underlying physical phenomena are well understood, and stimulus properties can be precisely controlled. In olfaction, the situation is different. The presence of specific chemical compounds in the air (or water) is the root cause for perceived odors, but it remains unknown what organizing principles, equivalent to wavelength for light, determine the dimensions of odor space. Equally important, but less in the spotlight, odor stimuli are also complex with respect to their physical properties, including concentration and time-varying spatio-temporal distribution. We still lack a complete understanding or control over these properties, in either experiments or theory. In this review, we will concentrate on two important aspects of the physical properties of odor stimuli beyond the chemical identity of the odorants: (1) The amplitude of odor stimuli and their temporal dynamics. (2) The spatio-temporal structure of odor plumes in a natural environment. Concerning these issues, we ask the following questions: (1) Given any particular experimental protocol for odor stimulation, do we have a realistic estimate of the odorant concentration in the air, and at the olfactory receptor neurons? Can we control, or at least know, the dynamics of odorant concentration at olfactory receptor neurons? (2) What do we know of the spatio-temporal structure of odor stimuli in a natural environment both from a theoretical and experimental perspective? And how does this change if we consider mixtures of odorants? For both topics, we will briefly summarize the underlying principles of physics and review the experimental and theoretical Neuroscience literature, focusing on the aspects that are relevant to animals’ physiology and behavior. We hope that by bringing the physical principles behind odor plume landscapes to the fore we can contribute to promoting a new generation of experiments and models.

Comparative analysis of the boundary layer filtering of odor signals in the amblypygid (whip spider) species Paraphrynus laevifrons and Phrynus marginemaculatus

Amblypygids use a pair of modified walking legs (antenniform) as chemosensory and mechanosensory appendages. At the tip of these legs are covered in chemosensory sensilla, which the animals use to sample odor stimuli in their environment by moving the antenniform leg through the air. We designed a set of experiments to measure the filtering effect that aerodynamic boundary layers have on the temporal and spatial structure of chemical stimuli. In addition, two different species of amblypygids (Paraphrynus laevifrons and Phrynus marginemaculatus) that live in two distinct habitats were used for a comparative analysis. Pulses of a tracer molecule were quantified at different distances and flow velocities using an electrochemical detection system. Temporal attributes of the chemical pulses were extracted and were statistically compared across velocities, distances from the appendage, and the two species. Overall, the boundary layer significantly decreased the concentration and increased the duration of pulses for both species. This filtering effect was more pronounced for P. marginemaculatus than P. laevifrons, as the chemical signal was lower in concentration and longer in duration at any distance from the antenniform leg. It is speculated that the difference in boundary layer filtering, as a function of appendage morphology, is tuned to the different types of odor plumes in these animals’ native habitats.

Assessment of the Effects of Wastewater Treatment Plant Modernization by Means of the Field Olfactometry Method

Methodological aspects of odor studies in ex-post analyses for Polish wastewater management facilities were analyzed based on the example of a modernized and enlarged wastewater treatment plant (WWTP) in Mazovia, in the vicinity of the Warsaw agglomeration. It is a mechanical–biological treatment plant with increased efficiency of biogen removal, using activated sludge in the treatment process, with a maximum hydraulic capacity of 60,000 m3/day. Olfactometric research was carried out by means of a method based on identification and characterization of the odor plume emitted from the examined source. This paper presents the results of odor intensity assessment (in sensory examinations according to a 6-stage scale) and odor concentration measurement (using portable field olfactometers) after the completion of the project, and compares them with similar studies conducted before the commencement of the investment. A total of 10 measurement series were carried out before modernization, and 12 after modernization of the WWTP. Odor concentration and intensity were determined, and the current meteorological situation was assessed at the measurement and observation points (receptors) located within the premises (in total 462 points) and around the WWTP (342 points). In each series of measurements on the windward side of the treatment plant, the background of air pollution with odorous substances was marked. The research showed that air flowing into the area of the sewage treatment plant is clean in terms of odor. During the research, basic sources of odor nuisance were identified, and their impact before and after modernization was characterized. The results presented in radar diagrams show changes in the percentage distribution of frequency of occurrence of individual intensity values at receptor points within and outside the area of the treatment plant. After modernization, a significant decrease in the concentration of odor emitted from the sludge dewatering building and sludge containers was determined. The air-tightness of the sewage channel (covered with concrete slabs and sealed) resulted in a significant decrease in the concentration of odor emitted from this source. Waste (in particular, sewage sludge) collected in the emergency waste storage yard was identified as the main source of odor nuisance. The waste, even after modernization, was an emitter of odorous compounds spreading outside the area of the WWTP. Nevertheless, as a result of the investment, the desired effect of reduction of the degree of odor nuisance was achieved.

Encoding of Slowly Fluctuating Concentration Changes by Cockroach Olfactory Receptor Neurons Is Invariant to Air Flow Velocity.

The ON and OFF olfactory receptor neurons (ORNs) on the cockroach antenna display a high sensitivity for the rate at which odorant concentration changes. That rate of change acts as a gain control signal that improves the sensitivity of both ORNs for fluctuating concentration changes. By means of extracellular recording techniques, we find in both types of ORNs an increased gain for the rate of concentration change when the duration of the oscillation period increases. During long-period oscillations with slow concentration changes, the high gain for the rate of concentration change improves the ORNs ability to detect low rates of concentration changes when the fluctuations are weak. To be useful in plume tracking, gain control must be invariant to the air flow velocity. We describe that raising the level of the flow rate has no effect on the ON-ORN responses to concentration changes down to rates of 2%/s, but exerts a slight increase on the OFF-ORN response during these extremely low rates. At 4%/s, however, the OFF-ORN response is also unaffected by the flow rate level. The asymmetry corresponds with a generally higher sensitivity of the OFF-ORN to concentration changes. Nevertheless, the gain of both ORNs for the concentration rate change is robust against the air flow velocity. This makes possible an instantaneous analysis of the rate of concentration change for both directions of change by one or the other ORN. Therefore, the ON and OFF ORNs are optimized to encode concentration increments and decrements in a turbulent odorant plume.

Initial Characterization of a Subpopulation of Inherent Oscillatory Mammalian Olfactory Receptor Neurons.

Published evidence suggests that inherent rhythmically active or "bursting" primary olfactory receptor neurons (bORNs) in crustaceans have the previously undescribed functional property of encoding olfactory information by having their rhythmicity entrained by the odor stimulus. In order to determine whether such bORN-based encoding is a fundamental feature of olfaction that extends beyond crustaceans, we patch-clamped bORN-like ORNs in mice, characterized their dynamic properties, and show they align with the dynamic properties of lobster bORNs. We then characterized bORN-like activity by imaging the olfactory epithelium of OMP-GCaMP6f mice. Next, we showed rhythmic activity is not dependent upon the endogenous OR by patching ORNs in OR/GFP mice. Lastly, we showed the properties of bORN-like ORNs characterized in mice generalize to rats. Our findings suggest encoding odor time should be viewed as a fundamental feature of olfaction with the potential to be used to navigate odor plumes in animals as diverse as crustaceans and mammals.

Establishing the extent of odour plumes and buffers for waste handling facilities

Odour is a significant challenge for regulators of waste handling facilities due to the increasing demand for land surrounding these facilities. Many sites, including landfills, composters, abattoirs and rendering plants, that were once isolated are now close to residential areas. In some cases, this has contributed to odour impacts on residents living in those areas. Authorities have been reliant on odour modelling and odour design criteria to predict or estimate the distance at which impacts are likely to occur on sensitive land use. However, it is increasingly evident that reliance on modelling tools, and the estimated odour emission rates used in modelling, are not reflecting ground level observations. Environment Protection Authority Victoria (“EPA”) conducted six in-field odour monitoring campaigns between 2007 and 2017. We studied these six campaigns to understand the extent of odour plumes from waste handling facilities.The campaigns used odour surveillance methodology developed by EPA. They consisted of in-field odour assessments around common waste handling facilities such as composters, landfills, abattoirs and rendering plants. We used the results of surveillance in conjunction with reverse trajectory plotting to estimate the typical extent and frequency of odour plumes as a function of distance. The study showed that the application of consistent in-field odour assessment methodologies improved understanding of odour plumes, and hence increases the options available to manage impacts.

Extremely low neonicotinoid doses alter navigation of pest insects along pheromone plumes

The prevailing use of neonicotinoids in pest control has adverse effects on non-target organisms, like honeybees. However, relatively few studies have explored the effect of sublethal neonicotinoid levels on olfactory responses of pest insects, and thus their potential impact on semiochemical surveillance and control methods, such as monitoring or mating disruption. We recently reported that sublethal doses of the neonicotinoid thiacloprid (TIA) had dramatic effects on sex pheromone release in three tortricid moth species. We present now effects of TIA on pheromone detection and, for the first time, navigational responses of pest insects to pheromone sources. TIA delayed and reduced the percentage of males responding in the wind tunnel without analogous alteration of electrophysiological antennal responses. During navigation along an odor plume, treated males exhibited markedly slower flights and, in general, described narrower flight tracks, with an increased susceptibility to wind-induced drift. All these effects increased in a dose-dependent manner starting at LC0.001 - which would kill just 10 out of 106 individuals - and revealed an especially pronounced sensitivity in one of the species, Grapholita molesta. Our results suggest that minimal neonicotinoid quantities alter chemical communication, and thus could affect the efficacy of semiochemical pest management methods.

Towards a Harmonized Odour Guideline for Some Austrian Provinces

Currently some provinces in Austria attempt to set up a harmonized regulation for assessing odour nuisance. The Austrian laws do not stipulate that any nuisance is to be prevented, but only “unacceptable” nuisance. “Unacceptable” is not a scientific or medical term but needs to be interpreted in a legal context. In the new guideline different odour impact criteria (OIC) are set up with regard to the hedonic tone of odours. For each category a maximally allowed frequency is defined. Frequencies are to be assessed on the total number of hours of a year, where the computed 90th percentile within one hour is above a certain threshold concentration (e.g. 1 odour unit [ou] per m³). Such is termed an odour hour. Dispersion modelling is the major methodology for odour assessments. Unlike in Germany, no specific model is prescribed, but model developers need to prove the capability of their model to accurately simulate the 90th percentile odour concentration of an hour. For instance, the Lagrangian particle model GRAL, which is frequently used in Austria, offers a new module to compute the 90th percentile based on the work of Oettl and Ferrero (2017a). The 90th percentile is thereby a function of the three dimensional odour-concentration field and the atmospheric turbulence, thus, the model is able to take into account the effects of overlapping odour plumes, too. It could be demonstrated that modelled odour-hour frequencies using this novel approach are in very good agreement with observed odour hours assessed by field inspections following the new European standard EN 16841-1. Field inspections, therefore, may also be used for odour assessment, whenever modelling is not possible (e.g. unknown source strengths). OICs are derived upon dose-response relationships, which were established by evaluating historical citizen’s complaints using the dispersion model GRAL. Relationships between the percentage of annoyed residents and modelled odour-hour frequencies were found to be quite different for odorants having a very high potential of offensiveness and such with a moderate potential. Discontinuous odour sources are assessed by using OICs based on the 0.5th percentile evaluated for concentrations larger than 1 ou m-3. The corresponding concentration thresholds for the four distinguished hedonic tones were derived by matching the affected non-attainment areas resulting from the regulations for continuous sources with those resulting from the 0.5th percentile regulation.

A balance between aerodynamic and olfactory performance during flight in Drosophila.

The ability to track odor plumes to their source (food, mate, etc.) is key to the survival of many insects. During this odor-guided navigation, flapping wings could actively draw odorants to the antennae to enhance olfactory sensitivity, but it is unclear if improving olfactory function comes at a cost to aerodynamic performance. Here, we computationally quantify the odor plume features around a fruit fly in forward flight and confirm that the antenna is well positioned to receive a significant increase of odor mass flux (peak 1.8 times), induced by wing flapping, vertically from below the body but not horizontally. This anisotropic odor spatial sampling may have important implications for behavior and the algorithm during plume tracking. Further analysis also suggests that, because both aerodynamic and olfactory functions are indispensable during odor-guided navigation, the wing shape and size may be a balance between the two functions.

Combination of field inspection and dispersion modelling to estimate odour emissions from an Italian landfill

In the case of landfills, the determination of odour emissions is particularly complex. Up to now, no universally accepted methodology for sampling and assessing emissions from landfill surfaces has been established. Besides, the dependence of such emissions from some crucial environmental variables, such as wind speed, has not been univocally defined yet. In this study, odour dispersion modelling and plume inspections by human assessors were combined in order to estimate the odour emissions from a landfill in Southern Italy. Two substantially different approaches were compared: the one that considers emissions as a function of the wind speed blowing over the surface, counterposed to the one that considers odour emissions as constant, in agreement with the most recent studies on the matter. The comparison of the field assessments and the model clearly highlights that the first approach significantly overestimates the landfill odour emissions, whereas the use of a constant odour emission rate results in a much better correspondence between model outputs and field assessments, both in terms of shape and extension of the determined odour plume extents.

Quantification of airborne odor plumes using planar laser-induced fluorescence

Planar laser-induced fluorescence (PLIF) is used to quantify spatiotemporal structure of gaseous scalar plumes (Sc $$\approx 1.5$$ ) in a benchtop-scale low-speed wind tunnel. The study is motivated by a desire to understand variations in information content in odor plumes used by animals for navigation. Acetone vapor is used as a fluorescent odor surrogate and is released isokinetically to form a neutrally buoyant plume. Three cases are investigated: a near-bed scalar release at 10 cm/s, a freestream scalar release at 10 cm/s, and a second freestream scalar release at 20 cm/s. PLIF image data are collected at 15 Hz and processed to provide distributions of instantaneous concentrations. Spatial distributions of mean concentration, root-mean-square fluctuations, and concentration intermittency are presented, along with probability density functions of concentrations at select locations. The results demonstrate significant differences in spatiotemporal structure of the scalar plumes across the three tested cases. In particular, the near-bed plume is markedly different from those released in the freestream. The results have important implications for understanding gaseous plume structure. Specifically, the results suggest that different flow and release conditions control constraints and opportunities for animals using odor plumes for navigational purposes.

Odour impact from farms with animal husbandry and biogas facilities

Agricultural biogas facilities are usually combined with animal husbandry. Their siting near residential areas can lead to odour complaints by residents. The aim of this study was to identify relevant odour sources, to record odour impact, and to determine the main variables influencing odour impact. Therefore, a combined approach was designed to account for individual odour sources as well as the farms as a whole. On eight farms with cattle husbandry and biogas facilities, two of which kept pigs and poultry, the odour-relevant area sources ranged between 475 and 1810 m2. Solid manure from poultry, cattle and horses as well as grass cuttings, vegetable peelings, liquid-silage effluent and fermentation residues figured among the odour-intensive sources, in addition to biogas. Odour-plume inspections were performed at various distances from the farm, and assessors determined their odour perception and -intensities. The odour intensity in the downwind plume axis was explainable in a linear mixed-effects model by distance (p < 0.001), emitting surface area (p = 0.002) and wind speed (p = 0.018). As distance increased, odour intensity decreased by a factor of two per 50 m. Higher odour intensities resulted from larger surface areas in the animal enclosure, substrate storage, or especially odour-relevant sources. A mixture of odours was frequently perceived in the odour plume. If biogas escaped, an increase in odour impact was recognisable (p = 0.021). Biogas leakage should be avoided with a sufficiently large storage capacity, process optimisation, and regular servicing. In summary, animal husbandry and biogas facilities are to be viewed as an entire plant in terms of downwind odour perception. In planning processes for biogas facilities with animal husbandry, great care in the choice of site is called for, as are structural-technical and organisational measures for abatement.

Information-theoretic analysis of realistic odor plumes: What cues are useful for determining location?

Many species rely on olfaction to navigate towards food sources or mates. Olfactory navigation is a challenging task since odor environments are typically turbulent. While time-averaged odor concentration varies smoothly with the distance to the source, instaneous concentrations are intermittent and obtaining stable averages takes longer than the typical intervals between animals’ navigation decisions. How to effectively sample from the odor distribution to determine sampling location is the focus in this article. To investigate which sampling strategies are most informative about the location of an odor source, we recorded three naturalistic stimuli with planar lased-induced fluorescence and used an information-theoretic approach to quantify the information that different sampling strategies provide about sampling location. Specifically, we compared multiple sampling strategies based on a fixed number of coding bits for encoding the olfactory stimulus. When the coding bits were all allocated to representing odor concentration at a single sensor, information rapidly saturated. Using the same number of coding bits in two sensors provides more information, as does coding multiple samples at different times. When accumulating multiple samples at a fixed location, the temporal sequence does not yield a large amount of information and can be averaged with minimal loss. Furthermore, we show that histogram-equalization is not the most efficient way to use coding bits when using the olfactory sample to determine location.

Opening the chemosensory world of the lobster, Homarus americanus

The natural history of the American lobster, Homarus americanus H. Milne-Edwards, 1837, was described in detail as part of the general interest in marine biology in the late 19th century. A half-century ago, lobsters gained prominence in the biological analysis of underwater chemical sensing, using neurobiological, behavioral, and ecological approaches. Lobsters made us recognize different chemical sensing organs, each with their unique signal-filtering properties and behavioral functions, and they showed how they generate and control information currents for both odor dispersal and reception. This led to better understanding of the constraints that fluid motion places on odor signal analysis and sensor design. This, in turn, spurred construction of a lobster-inspired electronic nose to measure the temporal resolution of chemoreceptor organs used in odor plume analysis and tracking. Simultaneously, long-term field and naturalistic tank observations revealed their social structure involving sheltering, dominance fights, individual recognition by urine signals, courtship displays, cohabitation, and mating behavior. While most investigations focused on chemical signals, flow sensors were analyzed as part of antennule flicking and odor-flow coincidence detection. Mechanoreception plays an important role in smelling and tasting. Lobster vision contributes to opponent size estimates and recognition. Multisensory analysis will become increasingly important as is the chemical identification of the signals. Lobsters remain significant contributors to underwater sensory biology, influencing many other model systems, including other crustaceans, mollusks, sharks, and reef fish larvae. It has always been my privilege to work with so many inspiring students and colleagues.

American lobsters, Homarus americanus, use vision for initial opponent evaluation and subsequent memory

Many animals, including crustaceans, engage in dominance fights and thus the risk of damage. This makes opponent assessment a critical component of social information gathering. American lobsters, Homarus americanus (H. Milne-Edwards, 1837), are well known for surprisingly complex social behavior. Males fight for dominance, and winners are preferred by females. Fighting success is correlated with body and claw size. To avoid injury, opponents assess each other before and during a fight. The loser later recognizes the winner based on urine odor and retreats early from subsequent fights. Most research has explored recognition in the context of chemical ecology. Here, we describe four experiments testing the largely unexplored visual communication of male lobsters. Two experiments address evaluation within unfamiliar pairs. The first shows that the visual image of a lobster's own reflection in a mirror enhances attacks on an unfamiliar conspecific odor plume. The second shows that increasing differences in crusher claw size between opponents cause gradually decreasing fight duration; this negative correlation is maintained when either vision or olfaction is blocked. Blocking either sense caused similar increases in fight duration. Two additional experiments tested visual memory of opponents. Blindfolding the loser of a first fight abolished the decrease in second-fight duration seen in control fights, similar to previous results based on blocking olfaction. Finally, painting the face (carapace around the eyes and rostrum) of the winner in a second fight did not prevent recognition by the loser. Together, these results demonstrate that vision makes contributions to lobster communication, specifically opponent evaluation.

Moth-inspired navigation algorithm in a turbulent odor plume from a pulsating source.

Some female moths attract male moths by emitting series of pulses of pheromone filaments propagating downwind. The turbulent nature of the wind creates a complex flow environment, and causes the filaments to propagate in the form of patches with varying concentration distributions. Inspired by moth navigation capabilities, we propose a navigation strategy that enables a flier to locate an upwind pulsating odor source in a windy environment using a single threshold-based detection sensor. This optomotor anemotaxis strategy is constructed based on the physical properties of the turbulent flow carrying discrete puffs of odor and does not involve learning, memory, complex decision making or statistical methods. We suggest that in turbulent plumes from a pulsating point source, an instantaneously measurable quantity referred as a “puff crossing time”, improves the success rate as compared to the navigation strategies based on temporally regular zigzags due to intermittent contact, or an “internal counter”, that do not use this information. Using computer simulations of fliers navigating in turbulent plumes of the pulsating point source for varying flow parameters such as turbulent intensities, plume meandering and wind gusts, we obtained statistics of navigation paths towards the pheromone sources. We quantified the probability of a successful navigation as well as the flight parameters such as the time spent searching and the total flight time, with respect to different turbulent intensities, meandering or gusts. The concepts learned using this model may help to design odor-based navigation of miniature airborne autonomous vehicles.

Associative Learning of Food Odors by the European Paper Wasp, Polistes dominula Christ (Hymenoptera: Vespidae)

We investigated associative learning of food odors by the European paper wasp Polistes dominula Christ (Hymenoptera: Vespidae) because of consistent low rates of attraction to food materials in laboratory assays. We hypothesized that wasps in nature exhibit nonspecific food-finding behavior until locating a suitable food, and then respond more strongly and specifically to odors associated with that food reward. Female P. dominula workers exhibited higher rates of attraction in a flight tunnel to piped odors of fermented fruit purees following previous experience with that puree, compared to wasps with no prior experience with the fermented fruits. Attraction behavior included upwind-oriented flight and casting within the odor plume, indicative of chemoanemotaxis. Synthetic chemicals representative of volatiles P. dominula may encounter in nature while foraging was also tested. Similar increases in attraction responses occurred following feeding experience with a sugar solution that included either 3-methyl-1-butanol or pear ester, but not eugenol. These experimental results support the hypothesis of associative learning of food odors in P. dominula. We discuss the ecological relevance of our results and suggest an alternative approach to trap paper wasps in pest situations utilizing learned chemical attractants.