THERMAL CHARACTERISTICS OF MORIMUS ASPER FUNEREUS ELYTRA BY USING LASER POINTER DANICA PAVLOVIĆ Photonics Center Institute of Physics, University of Belgrade, [email protected] DARKO VASILJEVIĆ Photonics Center Institute of Physics, University of Belgrade, darko@ ipb.ac.rs LJUBIŠA TOMIĆ Military Technical Institute, Belgrade, [email protected] DEJAN PANTELIĆ Photonics Center Institute of Physics, University of Belgrade, [email protected] IVANA KOSTIĆ Technical Test Center, Belgrade, [email protected] GORAN DIKIĆ The School of Electrical and Computer Engineering of Applied Studies, Belgrade, [email protected] Abstract: Morimus Asper Funereus is longhorn beetle with four black spots on elytra. In our experiment we used live Morimus asper Funereus and we illuminate him with sunlight, and various laser pointers (red at 660 nm, green at 532 nm and blue at 405 nm). Thermal camera FLIR SC620 (spectral range from 7.5 µm till 13 µm) is used for recording. Thermal characteristics and optical properties are studied in visible and infrared range. Results from optical analyses have shown rather large absorption in visible spectral range. Optical analysis has shown strong absorption in visible range (650 nm red laser pointer) and uniform emissivity of the whole body of the longicorn beetle. Possible military applications of the natural camouflage and absorption mechanism are outlined. Keywords: Infrared imaging, natural photonics, camouflage. 1. INTRODUCTION and it moves because of intolerable temperature rise. As the longicorn beetle moves we also move laser pointer in The aim of this paper is to analyze the potential order to heat the same spot on the body of a longicorn camouflage and thermal dissipation capabilities of a large beetle. The relative impact of laser radiation to longicorn beetle Morimus asper funereus. We intended to temperature raise and indirectly on absorption of heat is determine efficiency of heat dissipation of this insect, as presented in this paper. well as its response to a thermal impulse. The Morimus asper funereus has recognizable gray body 2. DESCRIPTION OF MORIMUS ASPER with four black spots. They serve as camouflage in their FUNEREUS environment (beech forest) and we assume that insects also use them to control body temperature. Morimus asper funereus (Fig. 1) (fam. Cerambycidae, subfam. Lamiinae), is a large longicorn beetle with body Experimental setup is designed to allow comparison of length of 15 – 40mm [1]. The species is characterized by temperature change of two live longicorn beetles one grey elytra with four black patches. Coloration and irradiated only with sun radiation and other with sun velvety appearance of the elytra comes from dense radiation and red laser pointer radiation. Small tomentum of setae, grey hairs and black scales, embedded measurement area (8x8 pixels) are positioned on the body in elytral surface. This saproxylic beetle inhabits middle of longicorn beetle in order to measure maximum and southern Europe, where it feeds on tree bark of beech, temperature of heated longicorn beetle. oak, ash, poplar or maple [2]. The hind wings (alae) of the We presented thermal images and corresponding M.asper funereus are reduced and the species is flightless diagrams of temperature rise of two live longicorn [3]. The species is strictly protected in Europe (and beetles. One longicorn beetle is only irradiated with sun Serbia) by the Anex II of the Habitat Directive light and it is motionless. Other longicorn beetle is 92/43/CEE. Within the IUCN Red List of Threatened irradiated with sun light and red laser pointer (650 nm) Species, it is designated as vunerable (A1c) (IUCN Red THERMAL CHARACTERISTICS OF MORIMUS ASPER FUNEREUS ELYTRA BY USING LASER POINTER OTEH 2020 List of Threatened Species, 2018). We collected a limited longicorn beetles natural environment. The longicorn number (ten individuals) of insects during the summer of beetle can move along the twig. 2018 on Mt. Avala, near the city of Belgrade, with the Cooling of the test sample, previously heated by means of permission of the Serbian Ministry of Environmental a short laser pulse, was monitored using a commercial Protection (N°:353-01 -1310/2018-04). thermal camera "FLIR SC620", operating in the spectral Adults od M. asper funereus are considered to be long- range from 7.5 to 13 μm with FLIR T197189 macro lens. lived [4,5]. The period of the year when they are active This type of camera has a focal plane matrix of 640x480 depends on the latitude and altitude they are located on. consisting of semiconductor detector (Vanadium Oxide - Depending on that, they can be found from April to VOx). October, with the highest numbers and activities from the Each detector pixel of a camera focal plane matrix end of May to the beginning of August [6]. In order to measures the intensity of infrared radiation. These values survive “such a long period”, M. asper funereus adults can be represented on a monitor as a thermal image coded must feed. According to various studies, they feed on tree in shades of gray or in color and can be converted to bark, plant juices and fruits [3]. Important feature is that temperature values using the appropriate table [8]. the species has reduced hing wings and its flightless [6], therefore it doesn’t need heating of the thoracic muscles due to take-off. Picture 1. M. asper funereus with four black patches on its elytra Picture 2. The experimental setup. Numbers 1 and 2 designate specimens of M. asper funereus. During the collection of individuals of M. asper funereus we have noticed that they do not prefer direct sunlight. In order to obtain optimal experimental results zoom has We have never found them on the trunks that were been set manually. After that, the all other parameters directly exposed to Sun radiation. Even when we (ambient temperature, emissivity, the distance of the subjected them to the sunlight they would be hiding object from the thermal imaging camera, humidity, etc.) themselves in the shadow. This was confirmed by other have been found. Measurements, presented in this paper, research, which state that this species is actually active have been carried out at short distances, (about 50 cm) during the evening and at night [4, 7]. and are not affected by atmospheric absorption. In paper [6] authors have determined that the highest Thermal imaging camera allows conversion of spatially activity of the species was between 20:00 i 24:00 h. inhomogeneous distribution of radiation flux of scene, However, authors declare that individuals of M. asper due to differences in the distribution of temperature funereus were seen during the day, but that the number and/or emissivity, in the visible image. The right choice was only 30% compared to the maximum recorded (in the of measuring geometry and correct interpretation of the evening and at night). This is in complete correlation with results is based on the knowledge of the spatial and our research about thermal characteristics and temperature resolution (sensitivity) of thermal imaging morphology of photonic structures on the elytra of M. cameras. asper funereu. 4. ANALYSIS OF RESULTS 3. EXPERIMENTAL SETUP Two thermograms are shown on picture 3. The first is The test equipment comprised a laser pointer, a thermal reference thermogram when both longicorn beetles are camera and a personal computer (PC), which recorded irradiated only with sunlight at the beginning of digital data in real time. The surface of test sample recording. (Morimus asper funereus) was heated using the red laser The second thermogram is when the longicorn beetle on pointer (650 nm), positioned at a distance of 50 cm from the twig is irradiated also with red laser pointer (4 frames the sample. Picture 2 shows the experimental setup with after starting laser pointer). two live longicorn beetles. One is on the bottom of transparent plastic box and other is on a twig to simulate THERMAL CHARACTERISTICS OF MORIMUS ASPER FUNEREUS ELYTRA BY USING LASER POINTER OTEH 2020 thermogram when both longicorn beetles are irradiated with only sunlight. The recording speed is 60 frames per second and measurement regions of interest on both longicorn beetles are squares 8x8 pixels. The measurement area AR01 is on the body of longicorn beetle on the twig. This is main measurement area where temperature rise because of laser radiation will be measured. When the temperature become too high, the longicorn beetle starts to move. Because of that, we have two temperature maxima. The measurement area AR02 is on the body of longicorn beetle on bottom of box. This is Picture 3. Experimental setup thermograms 1) reference only reference measurement area because the longicorn thermogram two longicorn beetles are irradiated only with beetle is irradiated only with sunlight. As can be seen on the picture 4 the maximum temperature in measurement sunlight, 2) thermogram of the longicorn beetle irradiated st with red laser pointer area AR1 on the 1 frame is 20.5ºC. The maximum temperature on the measurement area AR2 is 21.4ºC. The longicorn beetle emissivity was determined by Both maximum temperatures are similar because both thermographic method with a tape of reference emissivity longicorn beetles are irradiated only with sunlight. 0.95. Estimated accuracy of temperature measurements at the body of longicorn beetle is in accordance with the specification of the measuring thermal imaging camera and amounts to 2C or 2% from the measured temperature value of the pixel on the camera focal plane matrix. The maximum temperature on the body of longicorn beetle which is on the bottom of box (measurement area AR02, picture 3-1) is 21.7ºC, while maximum temperature of the body of longicorn beetle on the twig is 20.6ºC (measurement area AR01, picture 3-1). Both maximum temperatures are similar because both longicorn beetles are irradiated only with sunlight.