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We describe an entomological dual-band 808 and 980 nm lidar system which has been implemented in a tropical cloud forest (Ecuador). The system was successfully tested at a sample rate of 5 kHz in a cloud forest during challenging foggy conditions (extinction coefficients up to 20 km–1). At times, the backscattered signal could be retrieved from a distance of 2.929 km. We present insect and bat observations up to 200 m during a single night with an emphasis on fog aspects, potentials, and benefits of such dual-band systems. We demonstrate that the modulation contrast between insects and fog is high in the frequency domain compared to intensity in the time domain, thus allowing for better identification and quantification in misty forests. Oscillatory lidar extinction effects are shown in this work for the first time, caused by the combination of dense fog and large moths partially obstructing the beam. We demonstrate here an interesting case of a moth where left- and right-wing movements induced oscillations in both intensity and pixel spread. In addition, we were able to identify the dorsal and ventral sides of the wings by estimating the corresponding melanization with the dual-band lidar. We demonstrate that the wing beat trajectories in the dual-band parameter space are complementary rather than covarying or redundant, thus a dual-band entomological lidar approach to biodiversity studies is feasible in situ and endows species specificity differentiation. Future improvements are discussed. The introduction of these methodologies opens the door to a wealth of possible experiments to monitor, understand, and safeguard the biological resources of one of the most biodiverse countries on Earth.

There are hundreds of thousands of moth species with crucial ecological roles that are often obscured by their nocturnal lifestyles. The pigmentation and appearance of moths are dominated by cryptic diffuse shades of brown. In this study, 82 specimens representing 26 moth species were analysed using infrared polarimetric hyperspectral imaging in the range of 0.95–2.5 µm. Contrary to previous studies, we demonstrate that since infrared light does not resolve the surface roughness, wings appear glossy and specular at longer wavelengths. Such properties provide unique reflectance spectra between species. The reflectance of the majority of our species could be explained by comprehensive models, and a complete parametrization of the spectral, polarimetric and angular optical properties was reduced to just 11 parameters with physical units. These parameters are complementary and, compared with the within-species variation, were significantly distinct between species. Counterintuitively to the aperture-limited resolution criterion, we could deduce microscopic features along the surface from their infrared properties. These features were confirmed by electron microscopy. Finally, we show how our findings could greatly enhance opportunities for remote identification of free-flying moth species, and we hypothesize that such flat specular wing targets could be expected to be sensed over considerable distances.

Insects play crucial roles in ecosystems, and how they disperse within their habitat has significant implications for our daily life. Examples include foraging ranges for pollinators, as well as the spread of disease vectors and pests. Despite technological advances with radio tags, isotopes, and genetic sequencing, insect dispersal and migration range remain challenging to study. The gold standard method of mark-recapture is tedious and inefficient. This paper demonstrates the construction of a compact, inexpensive hyperspectral fluorescence lidar. The system is based on off-the-shelf components and 3D printing. After evaluating the performance of the instrument in the laboratory, we demonstrate its efficient range-resolved fluorescence spectra in situ. We present daytime remote ranging and fluorescent identification of auto-powder-tagged honey bees. We also showcase range-, temporally- and spectrally-resolved free-flying mosquitoes, which were tagged through feeding on fluorescent-dyed sugar water. We conclude that violet light can efficiently excite administered sugar meals imbibed by flying insects. Our field experiences provide realistic expectations of signal-to-noise levels, which can be used in future studies. The technique is generally applicable and can efficiently monitor several tagged insect groups in parallel for comparative ecological analysis. This technique opens up a range of ecological experiments, which were previously unfeasible.

Insect monitoring is critical to improve our understanding and ability to preserve and restore biodiversity, sustainably produce crops, and reduce vectors of human and livestock disease. Conventional monitoring methods of trapping and identification are time consuming and thus expensive. Automation would significantly improve the state of the art. Here, we present a network of distributed wireless sensors that moves the field towards automation by recording backscattered near-infrared modulation signatures from insects. The instrument is a compact sensor based on dual-wavelength infrared light emitting diodes and is capable of unsupervised, autonomous long-term insect monitoring over weather and seasons. The sensor records the backscattered light at kHz pace from each insect transiting the measurement volume. Insect observations are automatically extracted and transmitted with environmental metadata over cellular connection to a cloud-based database. The recorded features include wing beat harmonics, melanisation and flight direction. To validate the sensor’s capabilities, we tested the correlation between daily insect counts from an oil seed rape field measured with six yellow water traps and six sensors during a 4-week period. A comparison of the methods found a Spearman’s rank correlation coefficient of 0.61 and a p-value = 0.0065, with the sensors recording approximately 19 times more insect observations and demonstrating a larger temporal dynamic than conventional yellow water trap monitoring.

Insect pest management is a very important aspect for plant protection in crops production. Remote sensing provides a large number of techniques that are beneficial in entomological research. Although entomological radars have been used for studying migrations of insects for many years, most of entomological radar studies have been vertically tracing high-altitude migration behaviour of insects. Light detection and ranging (lidar) is a counterpart to radar, now operating in the optical part of the electromagnetic spectrum, which has been recently applied for monitoring of insects at low altitude. Such techniques, in particular low-cost continuous-wave (CW) bi-static systems based on the Scheimpflug arrangement, have been rapidly developing during the last decade. As a result, optical methods present new and fascinating possibilities. Based on experience from a 2-week field campaign in rice paddy fields, we here present an overview of lidar remote sensing applied to the Chinese scene. The capability of a CW Scheimpflug lidar system in monitoring the insects was studied. We present results on insect abundance in relation to time of the day and weather conditions. We also identified insect species by analysing wing-beat frequencies and studied their attraction to ultraviolet (UV) lamp located close to the horizontal laser sampling path during night time. Results showed that the insect species were abundant, that insects detected by the lidar system were attracted to light and that light rain increased the insect activity. The lidar detection system had a high read-out frequency, enabling the estimation of insect wing-beat frequencies. (Less)

In this paper, we use a novel spectral polarimetric optical tomographic imaging goniometer to investigate the scattering properties of Anopheles malaria mosquitoes to aid in their detection and identification in entomological lidar applications. Mosquitoes were mounted on a turn table, on which they were illuminated from different angles with linearly polarized near-infrared light and rotated. Thus, aspect-dependent optical cross sections were retrieved in backscatter and extinction mode. The backscattering and extinction properties of male and female mosquitoes were further condensed into a pair of parameters. We investigate the wings and bodies of mosquitoes together and independently, and conclude that the wings of mosquitoes strongly scatter copolarized light and that the degree of linear polarization of light scattered by insect bodies is independent of the aspect. In lidar measurements, light scattered by insect wings can be separated from light scattered by insect bodies due to the oscillatory wing beats. Therefore, obtaining the scattering properties of bodies and wings independently is of particular interest. Finally, we conclude that 808 nm light is well suited for detecting specular reflexes produced by Anopheles wings, which has large implications for the design of entomological lidar instruments used to study malaria mosquitoes.

Worldwide, farmers use insecticides to prevent crop damage caused by insect pests, while they also rely on insect pollinators to enhance crop yield and other insect as natural enemies of pests. In order to target pesticides to pests only, farmers must know exactly where and when pests and beneficial insects are present in the field. A promising solution to this problem could be optical sensors combined with machine learning. We obtained around 10,000 records of flying insects found in oilseed rape (Brassica napus) crops, using an optical remote sensor and evaluated three different classification methods for the obtained signals, reaching over 80% accuracy. We demonstrate that it is possible to classify insects in flight, making it possible to optimize the application of insecticides in space and time. This will enable a technological leap in precision agriculture, where focus on prudent and environmentally-sensitive use of pesticides is a top priority.

Forestry is raising concern about the outbreaks of European spruce bark beetle, Ips typographus, causing extensive damage to the spruce forest and timber values. Precise monitoring of these beetles is a necessary step towards preventing outbreaks. Current commercial monitoring methods are catch-based and lack in both temporal and spatial resolution. In this work, light scattering from beetles is characterized, and the feasibility of entomological lidar as a tool for long-term monitoring of bark beetles is explored. Laboratory optical properties, wing thickness, and wingbeat frequency of bark beetles are reported, and these parameters can infer target identity in lidar data. Lidar results from a Swedish forest with controlled bark beetle release event are presented. The capability of lidar to simultaneously monitor both insects and a pheromone plume mixed with chemical smoke governing the dispersal of many insects is demonstrated. In conclusion, entomological lidar is a promising tool for monitoring bark beetles.

Here we present recent advances and applications of profiling biological targets with Scheimpflug lidar. In particular we demonstrate applications for profiling the aerofauna and classifying various groups of species. Based on lidar data over the Ivorian countryside we investigate range dependent detection limits by comparing data with distinct sample rates and pulse energies.

We present a fluorosensor for the detection of laser-induced autofluorescence of zooplankton in marine environments. The sensor uses an inexpensive 410 nm laser diode as excitation source and simultaneously measures two fluorescence bands, 500-550 nm and 675-725 nm, using two identical 16-bit linear array detectors. We show continuous measurements at 200 Hz of zooplankton swimming through a water volume illuminated by the 410 nm laser. The sensor can distinguish salmon lice (Lepeophtheirus salmonis) larvae from an algae-eating reference species (Acartia tonsa) with a sensitivity of up to 99%. The system successfully differentiates the two species using mixed-species cultures at different ratios. This work shows the potential of fluorescent pest monitoring in the salmon farming industry and paves the way for single-ended aquatic lidars.

Despite numerous studies of selection on position and number of spectral vision bands, explanations to the function of narrow spectral bands are lacking. We investigate dragonflies (Odonata), which have the narrowest spectral bands reported, in order to investigate what features these narrow spectral bands may be used to perceive. We address whether it is likely that narrow red bands can be used to identify conspecifics by the optical signature from wing interference patterns (WIPs). We investigate the optical signatures of Odonata wings using hyperspectral imaging, laser profiling, ellipsometry, polarimetric modulation spectroscopy, and laser radar experiments. Based on results, we estimate the prospects for Odonata perception of WIPs to identify conspecifics in the spectral, spatial, intensity, polarization, angular, and temporal domains. We find six lines of evidence consistent with an ability to perceive WIPs. First, the wing membrane thickness of the studied Odonata is 2.3 μm, coinciding with the maximal thickness perceivable by the reported bandwidth. Second, flat wings imply that WIPs persist from whole wings, which can be seen at a distance. Third, WIPs constitute a major brightness in the visual environment only second after the solar disk. Fourth, WIPs exhibit high degree of polarization and polarization vision coincides with frontal narrow red bands in Odonata. Fifth, the angular light incidence on the Odonata composite eye provides all prerequisites for direct assessment of the refractive index which is associated with age. Sixth, WIPs from conspecifics in flight make a significant contribution even to the fundamental wingbeat frequency within the flicker fusion bandwidth of Odonata vision. We conclude that it is likely that WIPs can be perceived by the narrow red bands found in some Odonata species and propose future behavioral and electrophysiological tests of this hypothesis. (Less)

Surveying disease vectors is currently excessively laborious for continuous and widespread monitoring. Wing beat modulation spectroscopy gives opportunity for species and sex recognition in electronic traps or mosquito target classification in lidar. We used a polarimetric dual-wavelength-band laboratory system to record kHz modulated backscattered light from insects. The system operates in the near and short-wave infrared at 808 nm and 1550 nm and retrieves both co- and depolarized light. Here we give clues on the harmonic content and covariance of four mosquito species and fruit flies. Further, we interpret the interdependence of harmonic strengths when insects transit the probe volume with random heading direction and provide correlation matrices for coherent and incoherent light. Using the obtained parameters, we demonstrate that species that are difficult to distinguish with microscope can be classified with high accuracy. The results are valuable for understanding wingbeat harmonics in relation to heading and valuable for optimal sensor design for disease vector surveillance.

A molecular laser-radar system, based on the Scheimpflug principle, has been constructed and demonstrated for remote sensing of atmospheric CO

The ever-increasing worldwide environmental awareness has prompted much effort to minimize humanity's ecological footprint. This has led to increased demands for reliable technologies for assessing the current situation as well as the efficiency of new policies and interventions. In particular, CO 2 -monitoring has attracted lots of attention as CO 2 is the greenhouse gas that is emitted in the largest quantities [1].

We present an efficient fiber source designed for continuous-wave differential absorption light detection and ranging (CW DIAL) of atmospheric CO

A dual-band continuous-wave (CW) light detection and ranging (lidar) system has been developed for particle classification. In this lidar system, the range-resolved atmospheric backscattering signal is recorded by an optical imaging system satisfying the Scheimpflug principle instead of the conventional time-of-flight approach. It is thus possible to employ low-cost and compact CW diode lasers, facilitating the development of a robust multiple-wavelength atmospheric lidar system that can attain high accuracy of the retrieved parameters of atmospheric particles. The present work demonstrates a dual-band Scheimpflug lidar system employing two diode lasers at 405 nm (0.5 W) and 808 nm (3.2 W). Exposures are milliseconds apart and interpolated. Measurements of various types of particles and smoke have been performed to verify the feasibility of using the present system for improved particle classification and sizing, for the situation when plumes were dilute and no significant opacity was detected.

Monitoring the aquatic environment and the life of free-floating organisms remains on the borderline of our technical capabilities. Therefore, our insights into aquatic habitats, such as, abundance and behavior of organisms are limited. In order to improve our understanding of aquatic life, we have developed a low-cost inelastic hyperspectral lidar with unlimited focal depth and enough sensitivity and spatiotemporal resolution to detect and resolve position and behavior of individual submillimeter organisms. In this work, we demonstrate elastic as well as molecular ranging by using the water Raman band, and by observing fluorescence from chlorophyll and from dye-tagged organisms. We present an aquatic laser-diode-based inelastic light detection and ranging (lidar) system with unprecedented sensitivity, spatiotemporal resolution and number of spectral bands. Our system offers new opportunities for quantitative in situ studies of aquatic organisms, and has the potential to considerably advance our understanding of biological life in aquatic systems. (Figure presented.). (Less)

The pace at which the world's ecosystems and biodiversity of, e.g., pollinators decline is currently at a rate where it is challenging to document. In recent years, our group has made an effort to bridge the disciplines of laser remote sensing and biophotonics, and we have developed lidar methods for inventorying the biosphere. Here, we present an effective method for extracting fauna observations from atmospheric lidar data and reducing the observations to a set of descriptive parameters. Kilohertz-lidar data are used, the essential steps are walked through and a glimpse of the obtainable data product is presented.

Wind turbines have considerable impact on flying animals, particularly bats, which are sometimes killed in large numbers by the moving rotors. A longstanding question remains why bats are attracted to wind turbines and risk their lives among the moving rotor blades. One hypothesis is that they feed on insects swarming around the turbine towers and another is that they congregate there to court. The two are not mutually exclusive and may occur more or less simultaneously. It has been difficult to distinguish these hypothesis, because techniques that permit observations of small insects over the relevant distances (~100 m) in the dark are lacking. In this study, we monitored insects at the top of a wind turbine using a novel high-resolution Scheimpflug lidar. The instrument was employed around dusk during ten late summer nights in 2018, with the principal aim to evaluate its performance under real field conditions. Insect swarms were observed near the top of the turbine tower on every night. They appeared in short intervals and varied in density, timing, exact location and size of the swarming insects from day to day. Swarms formed in the afternoon and either dispersed around sunset before the emergence of bats, or remained until darkness, when bats arrived at the turbine. Some of the bats fed there, as indicated by ultrasonic feeding-buzzes, and also engaged in social interactions possibly including courtship, as indicated by song-flights. Daily variation in the formation, dispersal and behavior of the insect swarms appeared to be influenced by temperature and wind speed and also differed among the insect species.

Acquisition of entomological data with high-frequency lidar is an emerging research field in rapid development. The technique offers very high numbers of observations per time unit, suitable for statistical models. In this work, we use a near-infrared Scheimpflug lidar with a sampling frequency of 3.5 kHz to assess the activity of free flying organisms. In-situ measurements were done during the rainy season in Ivory Coast, and hierarchical cluster analysis was used to quantify the amount of unique modulation signatures. Here we propose a method to estimate the number of observed species within a certain air volume for a given time span. This paves the way for rapid in-situ biodiversity assessment in accordance with recent priorities for protection of pollinator diversity during global changes.

A portable Lidar system developed for large-scale (~1-20 m) combustion diagnostics is described and demonstrated. The system is able to perform remote backscattering measurements with range and temporal resolution. The range resolution is obtained by sharply imaging a part of the laser beam onto a CMOS-array or ICCD detector. The large focal depth required to do this is attained by placing the laser beam, the collection optics and the detector in a so-called Scheimpflug configuration. Results from simulations of the range capabilities and range resolution of the system are presented and its temporal resolution is also discussed. Various applications, important for combustion diagnostics, are also demonstrated, including Rayleigh scattering thermometry, aerosol detection and laser-induced fluorescence measurements. These measurements have been carried out using various continuous-wave GaN diode lasers, emitting in the violet-blue (405 – 450 nm) wavelength regime. It is anticipated that Scheimpflug Lidar will provide a useful and versatile diagnostic tool for combustion research, not only for fundamental studies, but in particular for applications at industrial sites.

We present a dual-wavelength polarimetric measurement method to distinguish species and sexes of disease transmitting mosquitoes in flight. By measuring co- and de-polarized backscattered light at 808 and 1550 nm, the degree of linear polarization, wingbeat frequency, reflectance, spectral ratio and glossiness of mosquitoes can be retrieved. Body and wing contributions to these signals can be separated. Whereas the optical cross-section is sensitive to the aspect of observation, thus the heading direction of the insect in flight, we demonstrate that polarimetric- and spectral- band ratios are largely invariant to the aspect of observation. We show that wing glossiness, as well as wing- and body-spectral ratios are particularly efficient in distinguishing Anopheles coluzzii and Anopheles arabiensis, two closely related species of malaria vectors. Spectral- and polarimetric ratios relate to microstructural and melanization features of the wing and body of these species. We conclude that multiband modulation spectroscopy is a useful expansion of the parameter space that can be used to improve specificity of entomological lidars.

Atmospheric dual-band Scheimpflug lidar is demonstrated at 980 and 1550 nm. Signals are compared during three weather conditions, and the spatio-temporal resolution of the atmospheric structure is considered. The potential for aerosol classification is evaluated, and future directions are discussed.

We present a study of optical signatures of salmon lice and the ability to distinguish them from a reference zooplankton species. This forms the basis for developing an instrument for detecting salmon lice in situ.

A joint Chinese-Swedish field campaign of Scheimpflug continuous-wave lidar monitoring of rice-field flying pest insects was pursued in very hot July weather conditions close to Guangzhou, China. The occurrence of insects, birds and bats with almost 200 hours of round-the-clock polarization-sensitive recordings was studied. Wing-beat frequency recordings and depolarization properties were used for target classification. Influence of weather conditions on the flying fauna was also investigated.

This work proves the feasibility of a novel concept of differential absorption lidar based on the Scheimpflug principle. The range-resolved atmospheric backscattering signal of a laser beam is retrieved by employing a tilted linear sensor with a Newtonian telescope, satisfying the Scheimpflug condition. Infinite focus depth is achieved despite employing a large optical aperture. The concept is demonstrated by measuring the range-resolved atmospheric oxygen concentration with a tunable continuous-wave narrow-band laser diode emitting around 761 nm over a path of one kilometer during night time. Laser power requirements for daytime operation are also investigated and validated with single-band atmospheric aerosol measurements by employing a broad-band 3.2-W laser diode. The results presented in this work show the potential of employing the continuous-wave differential absorption lidar (CW-DIAL) technique for remote profiling of atmospheric gases in daytime if high-power [GRAPHICS] narrow-band continuous-wave light sources were to be employed.

We present a set of spectrally and temporally resolved clinical fluorescence data-with two separate excitation wavelengths-that was recorded in vivo. We demonstrate that data in the spectral and temporal domains are in certain ways coupled and provide a method for integrated and effective parameterization of spectrally and temporally resolved fluorescence (i.e., time-resolved emission spectra). This parameterization is based on linear algebra, matrix formulation and system identification. We demonstrate how to empirically extract single exponentially decaying components and provide rectified emission spectra without prior knowledge. We investigate the potential for improved cancer diagnostics according to the reduced parameters along the various domains. In this case, in terms of cancer diagnostics, we were unable to identify any benefits of simultaneously measuring both the temporal and spectral properties of the observed fluorescence. However, we note that this may be explained by an important experimental bias present in many studies of optical cancer diagnostics, namely, that, in general, suspected lesions always differ visually from the neighboring healthy tissue. (C) 2015 Elsevier B.V. All rights reserved. (Less)

The recent several years we developed the Scheimpflug lidar method. We combined an invention from the 19th century with modern optoelectronics such as diode lasers and CMOS array from the 21st century. The approach exceeds expectations of background suppression, sensitivity and resolution beyond known from time-of-flight lidars. We accomplished multiband elastic atmospheric lidars for resolving single particles and aerosol plumes from 405 nm to 1550 nm. We pursued hyperspectral differential absorption lidar for molecular species. We demonstrated a simple method of inelastic hyperspectral lidar for profiling aquatic environments and vegetation structure. Not least, we have developed polarimetric Scheimpflug lidar with multi-kHz sampling rates for remote modulation spectroscopy and classification of aerofauna. All these advances are thanks to the Scheimpflug principle. Here we give a review of how far we have come and shed light on the limitations and opportunities for future directions. In particular, we show how the biosphere can be resolved with unsurpassed resolution in space and time, and share our expectation on how this can revolutionize ecological analysis and management in relation to agricultural pests, disease vectors and pollinator problematics.

Effective monitoring of flying insects is of major societal importance in view of the role of insects as indispensable pollinators, destructive disease vectors and economically devastating agricultural pests. The present paper reports on monitoring of flying agricultural pests using a continuous-wave lidar system in a rice-field location in Southern China. Using a Scheimpflug arrangement, range resolution over several 100 m long observational paths was achieved. The system operates with two perpendicularly polarized near-infrared lasers, which are activated intermittently, and back-scattered radiation from insects was recorded by a linear array detector placed after a linear polarizer. Our polarization sensitive system was used to monitor the flying insect diurnal activity and also the influence of changes in weather conditions, e.g., the occurrence of rain. Activity strongly peaked at dusk and rose again, although to a lower extent, just before dawn. At the onset of rainfall, a strong increase in insect counts occurred which was interpreted as the rain-induced bringing down of high-altitude migrant insects.

A multispectral polarimetric optical detection system with kHz sample rates was implemented to determine mosquito species and sex in flight. This system measures backscattered and extinguished light from mosquitoes at two wavelengths in both co- and de-polarized modes. Two Silicon and Indium Gallium Arsenide sandwiched detectors were used to collect backscattered signals from mosquitoes. These detectors collect co- and de-polarized near infrared (NIR, 808nm) and shortwave infrared (SWIR, 1550 nm) light. A Silicon photodiode was also used to measure the extinction signal. The backscattered and extinguished signals were sampled at 20 kHz, with a bandwidth of the detector modules at around 4 kHz. This system was used to determine species and sex of five mosquito species (Aedes aegypti, Culex quinquefasciatus, Anopheles gambiae, Anopheles arabiensis and Anopheles quadriannulatus). One of the parameters that can be used for species and sex determination is wing-beat frequency (WBF), see Fig. 1. Different parameters such as optical cross-section, melanization and absolute reflectance can be used in addition to WBF and harmonics to determine insects. The fundamental wingbeat frequency of female Anopheles gambiae shown in fig. 1 is 527.3 Hz. Moreover, around 5 harmonics overtones are shown in the co-polarized NIR and SWIR signals. Specular reflection contributes to highly co-polarized backscatter, rapid details in the waveform and a content of higher harmonics. This is the reason why the higher harmonics are mainly apparent in the co-polarized NIR and SWIR backscattered signal. We encountered WBF up 950 Hz within the male Aedes aegypti species. The results of the study showed that it is possible to distinguish between species and sex when combining these parameters. The signals presented here could in principle be retrieved remotely by lidar on landscape scales [1,2]. This would allow mapping the individual movement behaviour of flying insects, identified down to sex and species. This revolutionary technique can have a huge impact on some of today's greatest challenges: First, studying disease vectors (e.g. mosquitoes with malaria) will help researchers to understand their behaviour and apply vector control methods more precisely spatially and temporally.

Assessment of biodiversity of pollinators on the landscape scale or estimation of fluxes of disease-transmitting biting midges constitutes a major technical challenge today. We have developed a laser-radar system for field entomology based on the so called Scheimpflug principle and a continuouswave laser. The sample-rate of this method is unconstrained by the round-trip time of the light, and the method allows assessment of the fast oscillatory insect wing-beats and harmonics over kilometers range, e.g., for species identification and relating abundances to the topography. Whereas range resolution in conventional lidars is limited by the pulse duration, systems of the Scheimpflug type are limited by the diffraction of the telescopes. However, in the case of sparse occurrence of the atmospheric insects, where the optical cross-section oscillates, estimation of the range and spacing between individuals with a precision beyond the diffraction limit is now demonstrated. This enables studies of insect interaction processes in-situ.