Estimating the relative abundance of emperor penguins at inaccessible colonies using satellite imagery

Emperor penguin (Aptenodytes forsteri) populations are useful environmental indicators due to the bird’s extreme reliance on sea ice. We used remote sensing technology to estimate relative adult bird abundance at two inaccessible emperor penguin colonies in the Ross Sea, Antarctica. We performed supervised classification of 12 panchromatic satellite images of the seven known Ross Sea colonies. We used regression to predict adult bird counts at the inaccessible colonies by relating the number of pixels classified as “penguin” in the satellite images of the accessible colonies to corresponding known adult bird counts from aerial photographs or ground counts. While our analysis was hampered by excessive guano and shadows, we used satellite imagery to differentiate between relatively small (<3,000 adult birds) and larger colonies (>5,000 adult birds). Remote sensing technology is logistically less intense and less costly than aerial or ground censuses when the objective is to document penguin presence and/or large emperor penguin population changes (e.g., catastrophic changes). Improvements expected soon in the resolution of the satellite images should allow for more accurate abundance estimates.     

Mapping species density of trees,shrubs and vines in a tropical forest,using field measurements,satellite multiespectral imagery and spatial interpolation

We estimated the number of species in a tropical forest landscape in Quintana Roo, Mexico, based on the relationship between reflectance values of satellite imagery and field measurements of plant species density (mean number of species per plot). Total species density as well as that of tree, shrub and vine species were identified from 141 sampling quadrats (16543 individuals sampled). Spatial prediction of plant diversity was performed using universal kriging. This approach considered the linear relationship between plant species density and reflectance values of Thematic Mapper™, as well as the spatial dependence of the observations. We explored the linear relationships between spectral properties of TM bands and the species density of trees, shrubs and vines, using regression analysis. We employed Akaike Information Criterion (AIC) to select a set of candidate models. Based on Akaike weights, we calculated model-averaged parameters. Linear regression between number of species and reflectance values of TM bands yielded regression residuals. We used variogram analysis to analyze the spatial structure of these residuals. Results show that accounting for spatial autocorrelation in the residual variation improved model R² from 0.57 to 0.66 for number of all species, from 0.58 to 0.65 for number of tree species, from 0.26 to 0.41 for number of shrub species and from 0.13 to 0.17 for species density of vines. The empirical models we developed can be used to predict landscape-level species density in the Yucatan Peninsula, helping to guide and evaluate management and conservation strategies.     

Satellite observations of main oceanographic processes to identify ecological associations in the Northern Arabian Sea for fishery resources exploration

Ecological associations are the inter-relationship between the species and their environment. Oceanographic processes like upwelling events and formation of eddies, rings, and fronts have been monitored using National Oceanic and Atmospheric Administration Advanced Very High Resolution (NOAA AVHRR) and Indian Remote Sensing Satellite-P4-Ocean Colour Monitor (IRS-OCM) data. Sea Surface Temperature (SST) and chlorophyll concentration (CC) images were derived from AVHRR and OCM, respectively. Upwelling event was monitored using AVHRR-SST by detecting the differences in surface water temperature. The formation of eddies, rings, cyclonic eddies, and anti-cyclonic eddies and their biological responses were studied using CC. Eddies and rings were found with high phytoplankton production in the form of bloom, which provide grazing ground for fishes. The anti-cyclonic eddies were found with very low CC, indicating the biological deserts in the ocean. The impacts of these processes on fish catch were studied using fishing operations data procured from Fishery Survey of India. In this paper, the occurrence of different oceanographic processes, their persistence, and relevance with catch statistics of fishery resources in the study area are discussed. The study explains the potentials of satellite remote sensing to establish the habitat linkage between oceanographic processes and fishery resources. Guest editor: V. D. Valavanis Essential Fish Habitat Mapping in the Mediterranean     

Climate,satellite imagery and the seasonal abundance of the tick Rhipicephalus appendiculatus in southern Africa: a new perspective

Abstract. Recent predictive models for the distribution of the African tick Rhipicephalus appendiculatus Neumann, based on the computer packages CLIMEX and BIOCLIM and data derived from meteorological satellites, and for the seasonal dynamics of the same tick using the computer simulation models ECFXPERT and T3HOST, all have their limitations. Statistical analysis of the relationships between the seasonal abundance of all three life stages of this tick and climatic and satellite-derived data from five sites in southern Africa, taken from the literature, supports a new perspective that it is the timing of the questing activity of the desiccation-vulnerable larvae that determines the pattern of the tick's seasonal dynamics. The timing of the activity of nymphs and adults is determined by temperature-dependent development rates plus the delaying phenomenon of photoperiod-sensitive diapause, the timing and duration of which have evolved to achieve maximum generation survival by ensuring the occurrence of eggs and larvae during periods of optimal climatic conditions. The most important environmental factor appears to be night-time minimum temperature, determining condensation and saturation deficit and thus the tick's ability to replenish moisture lost during the daytime and so to survive while questing for hosts. It is the larvae whose numbers are correlated most closely with these factors, consistent with earlier experimental results showing larvae to be most susceptible to desiccating conditions. There is a statistical linkage between larval tick numbers and satellite imagery, arising from the correlation between larval numbers and minimum temperature and saturation deficit conditions, and in turn the relationship between these climatic conditions and the subsequent vegetational changes monitored by the satellites. Moisture availability to larvae is likely to be the critical factor throughout the geographical range of R.appendiculatus, but the precise combination of climatic conditions that optimize moisture availability and questing tick survival can be expected to vary geographically. The relationships between ticks, temperatures and satellite data in parts of equatorial Africa have yet to be established. These correlative patterns highlight both the critical life stage and environmental factors when trying to understand temporal, and ultimately spatial, variations in tick abundance.     

BioFTF: An R package for biodiversity assessment with the functional data analysis approach

This paper presents the R package BioFTF, which is a tool for statistical biodiversity assessment in the functional data analysis framework. Diversity is a key topic in many research fields; however, in the literature, it is demonstrated that the existing indices do not capture the different aspects of this concept. Thus, a main drawback is that different indicators may lead to different orderings among communities according to their biodiversity. A possible method to evaluate biodiversity consists in using diversity profiles that are curves depending on a specific parameter. In this setting, it is possible to adopt some functional instruments proposed in the literature, such as the first and second derivatives, the curvature, the radius of curvature and the arc length. Specifically, the derivatives and the curvature (or the radius of curvature) highlight any peculiar behaviour of the profiles, whereas the arc length helps in ranking curves, given the richness. Because these instruments do not solve the issue of ranking communities with different numbers of species, we propose an important methodological contribution that introduces the surface area. Indeed, this tool is a scalar measure that reflects the information provided by the biodiversity profile and allows for ordering communities with different richness. However, this approach requires mathematical skills that the average user may not have; thus, our idea is to provide a user-friendly tool for both non-statistician and statistician practitioners to measure biodiversity in a functional context.     

Monitoring Karenia brevis blooms in the Gulf of Mexico using satellite ocean color imagery and other data

Harmful algal blooms (HABs) of Karenia brevis are a recurrent problem in the Gulf of Mexico, with nearly annual occurrences on the Florida southwest coast, and fewer occurrences on the northwest Florida and Texas coasts. Beginning in 1999, the National Oceanic and Atmospheric Administration has issued the Gulf of Mexico HAB Bulletins to support state monitoring and management efforts. These bulletins involve analysis of satellite imagery with field and meteorological station data. The effort involves several components or models: (a) monitoring the movement of an algal bloom that has previously been identified as a HAB (type 1 forecast); (b) detecting new blooms as HAB or non-HAB (type 2); (c) predicting the movement of an identified HAB (type 3); (d) predicting conditions favorable for a HAB to occur where blooms have not yet been observed (type 4). The types 1 and 2 involve methods of bloom detection requiring routine remote sensing, especially satellite ocean color imagery and in situ data. Prediction (types 3 and 4) builds on the monitoring capability by using interpretative and numerical modeling. Successful forecasts cover more than 1000 km of coast and require routine input of remotely sensed and in situ data.The data sources used in this effort include ocean color imagery from the Sea-Viewing Wide Field-of-View Sensor/OrbView-2 satellite and processed using coastal-specific algorithms, wind data from coastal and offshore buoys, field observations of bloom location and intensity provided by state agencies, and forecasts from the National Weather Service. The HAB Bulletins began in coordination with the state of Florida in autumn of 1999 and included K. brevis bloom monitoring (type 1), with limited advisories on transport (type 3) and the detection of blooms in new areas (type 2). In autumn 2000, we improved both the transport forecasts and detection capabilities and began prediction of conditions favorable for bloom development (type 4). The HAB Bulletins have had several successes. The state of Florida was advised of the potential for a bloom to occur at the end of September 2000 (type 4), and the state was alerted to the position of blooms in January 2000 and October 2001 in areas that had not been previously sampled (type 3). These successful communications of HAB activity allowed Florida agencies responsible for shellfish management and public health to respond to a rapidly developing event in a timely, efficient manner.     

Microclimate of daytime den sites in a tropical possum: implications for the conservation of tropical arboreal marsupials

Tree cavities are an important shelter site for a variety of vertebrate species, including birds, reptiles and mammals. Studies indicate that in most taxa favoured tree hollows are those in larger trees and higher from the ground, generally thought to be related to decreased predation risk and a more optimal thermal environment. However, neither of these ideas has been tested definitively. Here, we investigate the microclimate of daytime den sites in tree hollows of common brushtail possums in tropical northern Australia. We compare tree and hollow characteristics of dens known to be used by possums, and those not known to be used, to determine whether possums choose trees with microhabitats with a more favourable daytime microclimate. Possums chose to den in tree hollows which were on average 1.6 °C cooler during the day, and were more buffered from temperature extremes, than other potential den locations. Important factors explaining daytime temperatures between hollows included height of the hollow, entrance width and tree diameter. Tropical arboreal marsupials have been identified as being particularly vulnerable to climate change and there are calls to identify and preserve natural refuges, such as tree hollows, which could buffer them from extreme temperatures. Our results highlight the value of older, larger hollow-bearing trees as refuges from extreme temperature, the importance of which may become critical for some temperature-sensitive species under the combined effects of continuing habitat loss and climate change.     

Mapping the spatial distribution of plant diversity indices in a tropical forest using multi-spectral satellite image classification and field measurements

The relationships among alpha and beta diversity indices, computed from 141 randomly sampled quadrats, and the vegetation classes obtained by multi-spectral satellite image classification, were used as a strategy for mapping plant diversity in a tropical landscape mosaic. A relatively high accuracy of the land cover map was revealed by the overall accuracy assessment and the Cohen's Kappa statistic. Species accumulation models were used to evaluate how representative the sample size was the different vegetation types. A standard one-way, between-subjects ANOVA confirmed a significant reduction of the within-class variance of plant diversity with respect to their total variance across the landscape. Computed uniformity indices, to assess the internal uniformity of vegetation classes on the diversity indices, confirmed the goodness of the mapped classes in stratifying variability of plant diversity. This allowed for the use of the mapped classes as spatial interpolators of plant diversity values for estimation and up-scaling purposes. Finally, it was revealed that the plant diversity of the landscape depends, to a large extent, on the diversity contained in the most mature forest class, which is also the most diverse community in the studied area. High and moderate beta diversity values between mature forests and both the secondary associations and the first stages of succession, respectively, indicated that there is a significant contribution to the diversity of the landscape by those vegetation classes.     

Forecasting sagebrush ecosystem components and greater sage-grouse habitat for 2050: Learning from past climate patterns and Landsat imagery to predict the future

Sagebrush (Artemisia spp.) ecosystems constitute the largest single North American shrub ecosystem and provide vital ecological, hydrological, biological, agricultural, and recreational ecosystem services. Disturbances have altered and reduced this ecosystem historically, but climate change may ultimately represent the greatest future risk. Improved ways to quantify, monitor, and predict climate-driven gradual change in this ecosystem is vital to its future management. We examined the annual change of Daymet precipitation (daily gridded climate data) and five remote sensing ecosystem sagebrush vegetation and soil components (bare ground, herbaceous, litter, sagebrush, and shrub) from 1984 to 2011 in southwestern Wyoming. Bare ground displayed an increasing trend in abundance over time, and herbaceous, litter, shrub, and sagebrush showed a decreasing trend. Total precipitation amounts show a downward trend during the same period. We established statistically significant correlations between each sagebrush component and historical precipitation records using a simple least squares linear regression. Using the historical relationship between sagebrush component abundance and precipitation in a linear model, we forecasted the abundance of the sagebrush components in 2050 using Intergovernmental Panel on Climate Change (IPCC) precipitation scenarios A1B and A2. Bare ground was the only component that increased under both future scenarios, with a net increase of 48.98 km² (1.1%) across the study area under the A1B scenario and 41.15 km² (0.9%) under the A2 scenario. The remaining components decreased under both future scenarios: litter had the highest net reductions with 49.82 km² (4.1%) under A1B and 50.8 km² (4.2%) under A2, and herbaceous had the smallest net reductions with 39.95 km² (3.8%) under A1B and 40.59 km² (3.3%) under A2. We applied the 2050 forecast sagebrush component values to contemporary (circa 2006) greater sage-grouse (Centrocercus urophasianus) habitat models to evaluate the effects of potential climate-induced habitat change. Under the 2050 IPCC A1B scenario, 11.6% of currently identified nesting habitat was lost, and 0.002% of new potential habitat was gained, with 4% of summer habitat lost and 0.039% gained. Our results demonstrate the successful ability of remote sensing based sagebrush components, when coupled with precipitation, to forecast future component response using IPCC precipitation scenarios. Our approach also enables future quantification of greater sage-grouse habitat under different precipitation scenarios, and provides additional capability to identify regional precipitation influence on sagebrush component response.     

Coral spawning in the western Pacific Ocean is related to solar insolation: evidence of multiple spawning events in Palau

Coral reproductive schedules have long been related to concomitant increases in regional sea surface temperature (SST). Yet, corals also mass spawn in the tropics, where SSTs vary little throughout the year. Here we show that the rise toward and fall from solar insolation maxima, which is the electromagnetic energy incident on the surface of the earth, coincide with coral spawning events in tropical Palau. Two insolation maxima (a consequence of the vernal and autumnal equinoxes) in the tropics lead to multiple spawning events per year. SSTs are poor predictors of coral spawning in the tropics. Multiple spawning events increase the rate of genetic recombination, which in turn may facilitate the likelihood of speciation and explain, in part, the high coral diversity in the tropics. We also show that mass spawning coincides with near-maximum solar insolation (5.0–7.2 kWh/m²/day) events from 33°N to 30°S in the western Pacific Ocean, and should be considered as one of the primary variables driving coral reproductive cycles.     

The potential of the satellite derived green chlorophyll index for estimating midday light use efficiency in maize, coniferous forest and grassland

Light use efficiency (LUE) is an important variable in carbon cycle and climate change research. We present an investigation of remotely estimating midday LUE using the green chlorophyll index (CI_green) derived from the cloud-free Moderate Resolution Imaging Spectroradiometer (MODIS) images in maize, coniferous forest and grassland. Similar temporal patterns are observed in both canopy chlorophyll content and midday LUE which indicates that the chlorophyll content in the maize canopy servers as a proxy of midday LUE (R² = 0.736, p < 0.001). Therefore, the CI_green, tested as a good indicator of canopy chlorophyll content (R² = 0.840, p < 0.001), has been demonstrated to be a reliable candidate in providing reasonable estimates of midday LUE with determination coefficient R² equals to 0.820 and a root mean square error (RMSE) of 0.002 mol CO₂ per mol incident photosynthetic photon flux density (PPFD). Further validation of the prediction model derived from the maize site demonstrates that the CI_green has potential to be applied in the coniferous forest and grassland ecosystems with RMSE of 0.005 and 0.004 mol CO₂ mol⁻¹ PPFD, respectively. A comparison analysis between different vegetation types is included and these results could be helpful in the development of future LUE and terrestrial models.     

Prescribed moorland burning meets good practice guidelines: A monitoring case study using aerial photography in the Peak District,UK

Upland moors in the UK have been managed for centuries using rotational prescribed-burning, but in recent years there has been contentious debate over its continuing use due to varying effects on moorland ecosystem services. Prescribed-burning should only be carried out using good-practice codes, which include restrictions on the size, location and frequency of burns. Good burning practice is an indicator of management standards and habitat condition in moorland landscapes. However, there has been little attempt to assess management performance with respect to these restrictions. We investigated prescribed-burning on a case-study estate (Howden Moor) in the Peak District National Park from 1988 to 2009 using management maps and aerial photography. The annual area burned (0.9%) was far below recommendations (10%) and patches were in keeping with the target sizes specified (mean ± se: 2370 ± 70 m²). The risk of a large or escaped fire was very low, with less than 1% of fires greater than 15,000 m². However, only 28.9% of the total burnable area was burned, leaving the rest unmanaged and accumulating fuel. Future guidelines might recommend the application of prescribed-burning across the range of Calluna vulgaris growth phases, to reduce fuel load and promote biodiversity at the landscape scale. We show that vegetation mapping and aerial photography are an effective method for monitoring prescribed-burning practice on moorlands. The information derived from such monitoring studies should lead to greater confidence in the standard of prescribed-burning and adherence to good-practice guidelines and requirements imposed by statutory authorities.     

Impact of four silvicultural systems on birds in the Belgian Ardenne: implications for biodiversity in plantation forests

Uneven-aged management of conifer plantations is proposed as a way to increase the value of these forests for the conservation of bird diversity. To test this assumption, we compared the impact of four common silvicultural systems on bird communities, defined by cutblock size (large in even-aged silvicultural systems/smaller in uneven-aged silvicultural systems) and tree species composition (spruce/beech) in the Belgian Ardenne where beech forests have been replaced by spruce plantations. The abundances of bird species were surveyed in young, medium-aged and mature stands in 3–5 forests per silvicultural system (66 plots in all). The effect of silvicultural systems on bird species richness, abundance and composition were analysed both at the plot and at the silvicultural system levels. In plots of a given age, beech stands were richer in species. The composition of bird species at the plot level was explained by stand age and tree composition, but weakly so by stand evenness. For the silvicultural systems, bird species richness was significantly higher in even-aged and in beech forests, and bird species composition depended on the silvicultural system. This study emphasises the importance of maintaining native beech stands for birds and suggests that uneven-aged management of conifer plantations does not provide a valuable improvement of bird diversity comparatively with even-aged systems.     

Contribution by farmers' survival strategies to soil erosion in the Linthipe River Catchment: implications for biodiversity conservation in Lake Malawi/Nyasa

Sediment discharge into Lake Malawi is threatening its ecologicalimportance, thereby inflicting serious socio-economic consequences upon peopledependent on this ecosystem. The discharge is attributed to high rates oferosion in the Lake's catchment, principally occurring on agriculturalland. This study examines how survival strategies, such as expansion ofcultivated farmland and use of low fertilizer application rates, enhance thelikelihood of erosion in the Linthipe River Catchment – one of theLake's important river catchments. As such, it shows that the magnitude oferosion is significantly correlated to the amount of farmland cultivated byestate farmers and smallholders (r = 0.18,P = 0.03, and r = 0.19,P = 0.003 respectively). The low correlation coefficientsuphold the long-established fact that physical variables such as soilerodibility (vulnerability of soil to erosion), rainfall erosivity (thepotential of rainfall to cause erosion), and topography, also play major rolesin erosion processes. Nonetheless they do show that area of cultivated landcontributes to erosion. Additionally, the study shows that yields of importantcrops such as maize and tobacco are low because of insufficient use offertilizers. To compensate for the low yields, farmers rely on extending sizesof land that they cultivate thereby exposing more land to erosive forces ofrainfall. The study, therefore, concludes that Lake Malawi's biodiversityis under threat. In order to sustain the biodiversity, it is necessary toeliminate the need to increase farmland by means of agricultural intensificationthat incorporates appropriate soil-conservation measures.     

Coupling satellite data with in situ measurements and numerical modeling to study fine suspended-sediment transport: a study for the lagoon of New Caledonia

This paper investigates the potential of remotely sensed data to map turbidity in a coral reef lagoon and to calibrate a numerical model of fine suspended-sediment transport. Simultaneous measurements of turbidity depth-profile and above-water spectral reflectance integrated according Landsat 7 ETM+ band 2 spectral sensitivity provide a linear regression relationship for the southwest lagoon of New Caledonia (r²=0.95, n=40). This relationship is applied to an empirically atmospherically corrected Landsat ETM+ image of the lagoon acquired on October 23, 2002. A comparison between Landsat estimates of turbidity and concurrent measurements at 14 stations indicates that the mean standard error in the satellite-estimated turbidity is 17.5%. The numerical model introduced in Douillet et al. (2001) is used to simulate the transport of fine suspended sediments in the lagoon in October 2002. A calibration of the erosion rate coefficient required by the model is proposed using in situ turbidity profiles and the remotely sensed turbidity field. In situ data are used to tune locally the erosion rate coefficient, while satellite data are used to determine its spatial zonation. We discuss necessary improvements in coupled studies of fine-sediment transport in coastal zones, namely relationships between turbidity and sediment concentration, integration of wave influence in the model, and correction of bottom reflection in satellite data processing.     

Distribution of Tettigoniinae (Orthoptera, Tettigoniidae) bush-crickets in Turkey: the importance of the Anatolian Taurus Mountains in biodiversity and implications for conservation

The distribution of Tettigoniinae (Orthoptera, Tettigoniidae) specieswithin four phytogeographical provinces in Turkey is reviewed and presented onthe basis of field and collection studies during 1987–2001 andmiscellaneous data from previous literature. One hundred and sixty speciesbelonging to 28 genera have been recorded. The Anatolian species constituteapproximately 30% of the world-wide species of the subfamily, with a very highproportion (83%) being endemic or semi-endemic, nearly all of which arebrachypterous. Regarding the numbers of total and endemic species, theprovinces can be ordered as follows: Mediterranean > Irano-Anatolian >Euxin > Mesopotamia. Also, Anatolian Tettigoniinae have a very high rate ofendemism in each province; 84.1% in the Mediterranean, 78.1% in Irano-Anatolia,56.3% in Mesopotamia and 42.4% in Euxin. The two provinces in Anatolia havingthe greatest species diversity are also the two most mountainous provinces, soit is suggested that a primary factor in Tettigoniinae diversity is theAnatolian Taurus mountains. Finally, some conclusions are drawn on biodiversityand conservation of Tettigoniinae species in Anatolia and I have suggested 23species to be included in the 'IUCN Red List' under VU B2+ac.     

The fluorescence lidar technique for the remote sensing of photoautotrophic biodeteriogens in the outdoor cultural heritage: A decade of in situ experiments

Fluorescence lidar is a non-invasive, remote sensing technique that makes it possible to extend the application of the laser-induced fluorescence technique to the outdoor environment, where uncontrolled external conditions must be met. Although initially developed for the investigation of marine environment and vegetation, in the past decade this technique has been successfully applied to the field of the cultural heritage. Among other applications, the detection and characterisation of photoautotrophic biodeteriogens has become very promising: the method is based on the detection of chlorophyll a fluorescence, while fluorescent accessory pigments can be exploited for a rough classification of the biodeteriogens present on the surface. Early experiments on monuments date back to the mid 1990s, when fluorescence lidar point measurements were conducted on the Cathedral and Baptistery of Parma, Italy. Subsequently, the technique has taken further advantage of the introduction of imaging capabilities in lidar instrumentation and this has led to the acquisition of hyperspectral fluorescence maps over extended areas of several monuments from distances as great as 80 m. Here, we present the main achievements obtained in the outdoor cultural heritage so far and the latest developments in the technique.     

Engaging the broader community in biodiversity research: the concept of the COMBER pilot project for divers in ViBRANT

This paper discusses the design and implementation of a citizen science pilot project, COMBER (Citizens' Network for the Observation of Marine BiodivERsity, http://www.comber.hcmr.gr), which has been initiated under the ViBRANT EU e-infrastructure. It is designed and implemented for divers and snorkelers who are interested in participating in marine biodiversity citizen science projects. It shows the necessity of engaging the broader community in the marine biodiversity monitoring and research projects, networks and initiatives. It analyses the stakeholders, the industry and the relevant markets involved in diving activities and their potential to sustain these activities. The principles, including data policy and rewards for the participating divers through their own data, upon which this project is based are thoroughly discussed. The results of the users analysis and lessons learned so far are presented. Future plans include promotion, links with citizen science web developments, data publishing tools, and development of new scientific hypotheses to be tested by the data collected so far.     

The photomechanic infrared receptor for the detection of forest fires in the beetle Melanophila acuminata (Coleoptera: Buprestidae)

We recorded from single units of individual sensilla of the thoracic infrared (IR) pit organs of Melanophila acuminata. When the organ was stimulated with a thermal radiator whose emission spectrum was similar to that of a typical forest fire, units responded phasically with up to seven spikes within 30–40 ms at a radiation power of 24 mW cm⁻². In the experiments all wavelengths shorter than 1.6 μm were excluded by a longpass IR filter. Response latencies were about 4 ms and initial impulse frequencies were up to 250 impulses per second (ips). A single spike could be generated even when stimulus duration was only 2 ms. Reduction of total radiation power from 24 mW cm⁻² to 5 mW cm⁻² resulted in increased response latencies of 5–6 ms and the occurrence of only two to three spikes. Initial impulse frequencies decreased to 125 ips. According to our physiological results and calculations, Melanophila should be able to detect a 10-hectare fire from a distance of 12 km. Mechanical stimuli also evoked responses of the IR sensilla. All present morphological and physiological findings lead to the conclusion that the IR receptors of Melanophila must function by means of a hitherto undescribed photomechanic mechanism. Accepted: 1 November 1997