Effect of gamma radiation on the protective efficacy of Thuja orientalis essential oil on stored cowpea against Callosobruchus maculatus and Callosobruchus chinensis.

PURPOSE: Cowpea is an essential pulse food in several regions throughout the world. Essential oil isolated from Thuja orientalis unripe fruits exposed to gamma radiation at dose levels of 0, 1, 3 and 5 kGy was evaluated as cowpea seed protectant against Callosobruchus maculatus and Callosobruchus chinensis. MATERIALS AND METHODS: Cowpea seeds were treated with three rates of the oils from non-irradiated and irradiated fruits, 0.5, 1.5 and 3.0 g kg-1. Mortality of C. maculatus and C. chinensis adults after 3 and 7 days, progeny reduction and weight loss of cowpea seeds after 45 days were recorded for all treatments. RESULTS: The pronounced mortality of C. maculatus adults was achieved at the highest rate 3.0 g kg-1 of the irradiated oil with 5 kGy (98.3%). While in the case C. chinensis, all tested application rates induced marked adult mortality and a complete mortality (100%) resulted at two application rates (0.5 and 1.5 g kg-1) of irradiated oil with 5 kGy and 3.0 g kg-1 after 7 days. Strong progeny suppression of C. maculatus and C. chinensis was resulted at the highest rate of 3.0 g kg-1 of irradiated oil with 5 kGy (11.3 ± 0.3) and (8.5 ± 3.8) after 45 days of treatment, respectively. High protection of cowpea seeds with weight loss 0.5 and 1.4% for C. maculatus and C. chinensis was achieved at 3.0 g kg-1 of irradiated oil dose of 5 kGy, respectively after 45 days. CONCLUSIONS: Our results indicate that gamma irradiation of T. orientalis fruits improve the protective activity of their essential oil against C. maculatus and C. chinensis on stored cowpea seeds and the irradiated oil could be successfully used for management of these bruchid insects.

Assessment of the potential of non-thermal atmospheric pressure plasma discharge and microwave energy against Tribolium castaneum and Trogoderma granarium.

This study was carried out to investigate the efficacy of the non-thermal atmospheric pressure plasma produced with dielectric barrier discharge (APPD) using air as a processing gas and microwave energy to control Tribolium castaneum and Trogoderma granarium adults and larvae in wheat grains. Insects' mortality was found to be power and time-dependent. The results indicated that non-thermal APPD and the microwave have enough insecticidal effect on the target pests. From the bioassay, LT50's and LT90's levels were estimated, T. granarium larvae appeared more tolerant to non-thermal APPD and the microwave energy than adults 7 days post-exposure. The germination percentage of wheat grains increased as the time of exposure to the non-thermal APPD increased. On the contrary, the germination percentage of wheat grains decreased as the time of exposure to the microwave increased. In addition, changes in antioxidant enzyme activities, catalase (CAT), glutathione S-transferase (GST) and peroxidase, in adults and larvae were examined after 24 h post-treatment to non-thermal APPD at 15.9 W power level, which caused 50% mortality. The activity of CAT, GST and lipid peroxide in the treated larvae showed a significant increase post-exposure to the non-thermal APPD at 15.9 W power level. On the other hand, no significant change in GSH-Px activity was observed. Reductions in the level of glutathione (GSH) and protein content occurred in treated larvae in comparison with the control.

Impact of artificial light intensity on nocturnal insect diversity in urban and rural areas of the Asir province, Saudi Arabia.

Continuous urban developments have resulted in increased demand for street furniture, one of which is street light columns. Artificial light at night (ALAN) pose significant impacts on insect diversity in urban and rural areas. The ALAN is a significant driver of decline in insect diversity. This study evaluated the impact of light intensity and sky quality at night on insect diversity in rural and urban areas of the Asir province, Saudi Arabia. Insect traps were installed in both areas during night. Light intensity of nearby road lamps was measured using light meter, while sky quality was measured using sky quality meter. Rural areas exhibited low light intensity (10.33 flux/f.candle) and good sky quality (18.80 magnitude/arcsec2). Urban areas exhibited intense light (89.33 flux/f.candle) and poor sky quality (15.49 magnitude/arcsec2). Higher insect diversity was recorded for rural areas where insects belonging to seven orders (i.e., Diptera, Lepidoptera, Hemiptera, Hymenoptera, Coleoptera, Neuroptera, and Dermaptera) were collected. However, insects of four orders (i.e., Diptera, Lepidoptera, Hemiptera, and Neuroptera) were found in urban areas indicating low diversity. Lepidopteran insects were frequently recorded from rural areas indicating they are attracted to artificial light. It is concluded that excessive ALAN and poor sky quality at night disrupt insect biodiversity. Therefore, ALAN and sky quality must be considered responsible for decline in insect biodiversity along with other known factors.

Assessment irradiation effects on different development stages of Callosobruchus maculatus and on chemical, physical and microbiological quality of cowpea seeds.

Irradiation is a physical, environmentally friendly treatment which does not leave any residues in the product. It is increasingly used as an alternative to methyl bromide and other chemical fumigants for disinfestation of insect pest in stored grains. In this research, we try to evaluate the effect of low gamma irradiation doses in the range of 50-1200 Gy on the different stages of Callosobruchus maculatus. It was found that no adults emerged after irradiation of eggs at 450 Gy. No emerging adults (F1 generation) have been shown when larvae or pupae were exposed to 650 Gy. Also, no emerging adult has been shown from the parental C. maculatus adults irradiated with 650 Gy. When suppression of F1 generation was used for the measuring effective irradiation dose and phytosanitary efficacy, 650 Gy was required for disinfestation of cowpea seed weevils. The irradiation dose level of 650 Gy was used for the large-scale confirmatory tests applied to 27,754 adults of C. maculatus in cowpea seeds resulting in non F1 adults' production with a confidence level of 93.77%. All the physical and chemical characteristics of cowpea seeds were non-significantly (P ≤ 0.05) affected by the irradiation dose of 650 Gy. Meanwhile, this irradiation dose very slightly reduced the microbial load of cowpea seeds. We recommend the generic dose 650 Gy as the phytosanitary irradiation dose for the cowpea seed weevil.

Effect of gamma radiation as a post-harvest disinfestation treatment against life stages of the coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae).

Purpose: Gamma radiation is mainly used for disinfesting insect pests as an alternative for harmful fumigants. The specific dose of radiation is known to affect different developmental stages of insect pests. The study was conducted to determine the effective irradiation doses for inhibition of developmental stages and adult longevity of the coffee berry borer, Hypothenemus hampei (Ferrari). Materials and methods: Irradiation was carried with the following doses: five levels between 0.01 and 0.16 kGy for eggs, seven levels between 0.10 and 2.00 kGy for larva and prepupa, six levels between 0.10 and 1.60 kGy for pupa and ten levels between 0.10 and 3.20 kGy for adults. Results: Egg development was completely arrested at 0.160 kGy. A dose of 2.00 kGy caused 100% mortality in the first and second instar larva and 98.99% mortality in prepupa. The dose of 1.60 kGy prevented adult eclosion from the irradiated pupa. The adult mortality was 100% at 3.20 kGy. Conclusion: A dose of 3.20 kGy could successfully provide complete security from all developmental stages of H. hampei and prevent yield loss in green coffee as well as the spread of the pest.

Microwave Application for Controlling Oryzaephilus surinamensis Insects Infesting Dried Figs and Evaluation of Product Color Changes Using an Image Processing Technique.

In this study, microwave heating was employed for controlling Oryzaephilus surinamensis adult beetles infesting stored Iranian dried figs. The dried fig samples were artificially infested with O. surinamensis and then heated in a microwave oven (2,450 MHz) at power outputs of 450, 720, and 900 W for 20, 30, 40, and 50 s. Changes in the color of the samples after these microwave applications were evaluated for lightness (ΔL*), redness (Δa*), and yellowness (Δb*) using an image processing technique. Both parameters of microwave power and exposure time had significant effects on beetle mortality ( P < 0.01). A direct positive relationship was found between the mortality rate and microwave power. Complete mortality was achieved at 900 W and for 50 s. The color parameters of the dried fig samples did not change significantly. These results indicate that microwave irradiation can be introduced as an appropriate alternative to chemical fumigants without affecting product quality.

Hypoxic environment protects cowpea bruchid (Callosobruchus maculatus) from electron beam irradiation damage.

BACKGROUND: Electron beam (eBeam) irradiation and hermetic storage are safe and effective technologies to protect stored products. Although hypoxic environment improves performance of some irradiated insects, whether hypoxia affects irradiation of storage insects and impacts pest control efficacy remains to be investigated. RESULTS: Using cowpea bruchid (Callosobruchus maculatus) larvae, we showed that, relative to eBeam irradiation under normoxia, the adult emergence rate increased substantially if they were exposed to hypoxia prior to and during eBeam treatment. Conversely, exposure to hypoxia only after eBeam irradiation did not have this protective effect. eBeam irradiation caused an increase in reactive oxygen species (ROS) in normoxic larvae but not in hypoxic larvae. The activity of citrate synthase, a pace-making enzyme in the citric acid cycle, was suppressed under hypoxia but resumed normal function within hours of reoxygenation, suggesting that reduced mitochondrial activity, and thus less ROS production under hypoxia increased insect tolerance to irradiation. Furthermore, reoxygenation accelerated eBeam-induced glutathione-S-transferase activation and potentiated eBeam-enhanced catalase activities. Faster and stronger detoxification capacity in eBeam-irradiated, hypoxic larvae may have protected them from oxidative damage. CONCLUSION: Hypoxic environment enhanced radiotolerance of bruchid larvae, presumably due to limited ROS production and elevated antioxidant enzymatic activities after reoxygenation. © 2018 Society of Chemical Industry.

Effect of Gamma Irradiation on Fecundity, Sterility, and Female Sex Pheromone Production of Callosobruchus chinensis (Coleoptera: Bruchidae).

Azuki bean beetle, Callosobruchus chinensis (L.) (Coleoptera: Bruchidae), is a field-to-storage pest of legumes and its females produce sex pheromone components with two isomers: (2Z,6E)-7-ethyl-3,11-dimethyl-2,6,10-dodecatrienal (2Z-homofarnesal) and (2E,6E)-7-ethyl-3,11-dimethyl-2,6,10-dodecatrienal (2E-homofarnesal). Two-day-old virgin adults were treated with different doses (0, 200, 300, 400, 500, and 600 Gy) of gamma radiation and the effects on adult survivorship, fecundity, sterility, and pheromone production were studied. The longevity of both sexes and female fecundity were dose dependently affected by the gamma irradiation revealing that the fecundity was more reduced when the female adults were irradiated. Adults of both sexes were totally sterilized by the doses of gamma radiation tested in this study as depicted by the null hatchability of the laid eggs. The results from analyses by gas chromatography-mass spectrometry for solid phase micro-extraction revealed that both of the female sex pheromone components were significantly reduced by 300 Gy. Though significantly less, there was release of some amount of pheromone components by the irradiated female azuki bean beetles revealing the possibility of pheromonal attraction of males to the irradiated females. It is a pre-requisite for the successful sterile insect technology that the sterility of azuki bean beetle is induced without the total disruption of the calling behavior.

Identification of cytochrome P450 monooxygenase genes and their expression in response to high temperature in the alligatorweed flea beetle Agasicles hygrophila (Coleoptera: Chrysomelidae).

Cytochrome P450 monooxygenases (P450s) are a large class of enzymes that play essential roles in metabolic processes such as hormone synthesis and the catabolism of toxins and other chemicals in insects. In the present study, we identified 82 P450 genes using comprehensive RNA sequencing in the flea beetle Agasicles hygrophila, and all of the sequences were validated by cloning and sequencing. Phylogenetic analysis showed that the P450 genes in A. hygrophila fell into the mitochondrial clan, CYP2 clan, CYP3 clan and CYP4 clan and were classified into 20 families and 48 subfamilies. Most A. hygrophila P450 genes had high sequence homology with those from other coleopteran insects. To understand the effects of high temperatures on the metabolic processes of female and male adults, we studied the effects of two temperature regimes (constant temperature of 28 °C for 20 h with a 4-h period of high temperatures of 30 °C and 39 °C) on the expression levels of P450 genes in A. hygrophila using RT-PCR and qRT-PCR. The results showed that there were no differences in expression in 30 P450 genes between the control and high-temperature-treated A. hygrophila adults, while 22 P450 genes showed up-regulated expression and 19 P450 genes were down-regulated in A. hygrophila female adults after high-temperature treatment. For A. hygrophila male adults exposed to high temperatures, we found that 8 P450 genes had higher expression levels and 12 P450 genes had lower expression levels under the same conditions. The P450 genes are candidates that showed significantly different expression levels after high-temperature treatments in A. hygrophila adults, and further studies are needed to determine their possible roles in metabolic processes during the response to elevated temperatures.

Neurotransmitter-Loaded Nanocapsule Triggers On-Demand Muscle Relaxation in Living Organism.

This paper reports the on-demand artificial muscle relaxation using a thermosensitive liposome encapsulating γ-aminobutyric acid (GABA) inhibitory neurotransmitter. Muscle relaxation is not feasible in principle, although muscle contraction can be easily induced by electrical stimulation. Herein, thermosensitive liposomes (phase transition temperature = 40 °C) were synthesized to encapsulate GABA and were injected into a leg of a living beetle. The leg was wrapped around by a Ni-Cr wire heater integrated with a thermocouple to enable the feedback control and to manipulate the leg temperature. The injected leg was temporarily immobilized by heating it up to 45 °C. The leg did not swing even by electrically stimulating the leg muscle. Subsequently, the leg recovered to swing. The result indicates that GABA was released from liposomes and fed to the leg muscle, enabling temporal muscle relaxation.

Evidence of vitamin D synthesis in insects exposed to UVb light.

Vertebrates obtain the prohormone vitamin D primarily by endogenous cutaneous synthesis under ultraviolet b (UVb) exposure. To date, endogenous synthesis of vitamin D in insects has never been investigated. In an initial experiment, we exposed four insect species which differ in ecology and morphology (migratory locusts, house crickets, yellow mealworms and black soldier fly larvae (BSFL)) to a low irradiance UVb source. In a second experiment we exposed these species to a higher UV irradiance, and in a third we tested the effect of exposure duration on vitamin D concentrations in yellow mealworms. Low irradiance UVb tended to increase vitamin D3 levels in house crickets, vitamin D2 levels in BSFL and vitamin D2 and D3 in yellow mealworms. Higher UVb irradiance increased vitamin D3 levels in all species but BSFL. Both BSFL and migratory locusts had increased vitamin D2 levels. Longer UVb exposure of yellow mealworms increased vitamin D2 and increased vitamin D3 until a plateau was reached at 6400 IU/kg. This study shows that insects can synthesize vitamin D de novo and that the amounts depend on UVb irradiance and exposure duration.

Effects of Irradiation Dose on Sperm Production, Insemination, and Male Mating Possible Period in the Sweetpotato Weevil (Coleoptera: Brentidae).

The sterile insect technique (SIT) has been used for the control or eradication of target insect pests. To successfully apply SIT, it is very important to clarify the effect of irradiation on male reproduction in the target pest, because their mating and spermiogenesis abilities affect the success of eradication program. The sweetpotato weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae) is a notorious and worldwide pest of sweet potato. We investigated the effect of irradiation at five doses ranging from 0 (control) to 150 Gy on 9-d-old males. Survival rate of the control (no treatment) remained high from day 10 to 20 of adult life, whereas higher doses of irradiation reduced it, maximally by approximately 70%. Mating rates showed a similar tendency. Radiation dose neither affected sperm production nor sperm transfer at any dose, although spermiogenesis is active during the adult stage. However, radiation dose affected the lifetime total of ejaculated sperm number, likely because of fewer matings by irradiated males. These results suggest that use of a dose of 150 Gy or higher is appropriate for the final step of eradication of this weevil. At least, lower dose of irradiation may arise the inadequate sterilization, resulting in a failure of eradication program. We conclude that weekly release of sweetpotato weevil sterilized with high dose, achieving complete sterilization, could be useful for eradication program after reducing the population by male annihilation method.

The impact of infrared radiation in flight control in the Australian "firebeetle" Merimna atrata.

Infrared (IR) receptors are rare in insects and have only been found in the small group of so-called pyrophilous insects, which approach forest fires. In previous work the morphology of the IR receptors and the physiology of the inherent sensory cells have been investigated. It was shown that receptors are located on the thorax and the abdomen respectively and show an astounding diversity with respect to structure and the presumed transduction mechanism. What is completely missing, however, is any behavioral evidence for the function of the IR receptors in pyrophilous insects. Here we describe the responses of the Australian "firebeetle", Merimna atrata to IR radiation. Beetles in a restrained flight were laterally stimulated with IR radiation of an intensity 20% above a previously determined electrophysiological threshold of the IR organs (40 mW/cm2). After exposure, beetles always showed an avoidance response away from the IR source. Reversible ablation experiments showed that the abdominal IR receptors are essential for the observed behavior. Tests with weaker IR radiation (11.4 mW/cm2) also induced avoidance reactions in some beetles pointing to a lower threshold. In contrast, beetles were never attracted by the IR source. Our results suggest that the IR receptors in Merimna atrata serve as an early warning system preventing an accidental landing on a hot surface. We also tested if another fire specific stimulus, the view of a large smoke plume, influenced the flight. However, due to an unexpected insensitivity of the flying beetles to most visual stimuli results were ambiguous.

Elytra Absorb Ultraviolet Radiation but Transmit Infrared Radiation in Neotropical Canthon Species (Coleoptera, Scarabaeinae).

Strategies to deal with global radiation may be related to important aspects of species biology and ecology by reflecting, transmitting or absorbing the radiation of varying wavelengths differently. The elytra capacity to manage infrared, visible and ultraviolet radiations (from 185 to 1400 nm) was assessed with a spectrophotometric analysis in five Canthon species of dung beetles; we calculated the reflectance, transmittance and absorbance capacity of the elytra of these species. These species have different ecologies: two species preferentially inhabit forest areas (Canthon angularis and Canthon lividus lividus), two species preferentially inhabit open areas (Canthon chalybaeus and Canthon tetraodon) including agricultural crops, and one species does not present a clear habitat preference and can be found in both habitats (Canthon quinquemaculatus). All the species show a similar pattern in which the light from shorter wavelengths and higher frequencies is almost entirely absorbed by the elytra, while radiation from longer wavelengths and lower frequencies can mostly pass through the elytra. However, C. quinquemaculatus seems to have significantly higher rates of reflectance and transmittance in the visible- and near-infrared spectrum. This different pattern found in C. quinquemaculatus may be associated with its capacity to establish populations both in agricultural and forest areas.

Comparison of the trapping effect and antioxidant enzymatic activities using three different light sources in cockchafers.

Light traps have been widely used for controlling underground pests. However, very little is known regarding the relationship between trapping effect and antioxidant enzymatic activities using light irradiation in underground pests. Thus, we determined the trapping effect of three light sources of the frequoscillation pest-killing lamp on two species of cockchafers, Serica orientalis Motschulsky (Coleoptera: Melolonthidae) and Anomala corpulenta Motschulsky (Coleoptera: Rutelidae), and evaluated the effect of the same three light sources on the activities of their antioxidant enzymes. The catches of S. orientalis were significantly higher compared to A. corpulenta using light source A in peanut fields in China. After irradiation by light source A, the malondialdehyde (MDA) contents and activities of superoxide dismutase (SOD) and glutathione S-transferases (GST) in S. orientalis were significantly and marginally significantly lower compared to A. corpulenta. Taken together, these results indicated a weaker antioxidant enzyme activity response to light stress and a larger quantity of trapping catches using light irradiation in cockchafers. Thus, we proposed a potential negative relationship between trapping effect and antioxidant enzymatic activities in response to light irradiation in cockchafers.

Ultrastructure alterations induced by gamma irradiation in spermiogenesis of the ground beetle, Blaps sulcata: reference to environmental radiation protection.

Ultrastructure alterations in spermiogenesis of the ground beetle, Blaps sulcata (Coleoptera: Tenebrionidae) were studied in normal adult males and in two male groups irradiated by gamma rays of 3 and 16 µSv/h dose rate. Ultrastructure examination of irradiated sperms revealed many alterations both in the head and in the flagellum regions of mature sperm. Alterations of the head region included nuclei with uncondensed chromatin materials and irregular nuclear envelope. Abnormal flagella contained malformed mitochondrial derivatives and damaged axonemes in addition to the absence of accessory bodies. Bi- and multi-flagellate sperms (with two, three, and four axonemes) were the most common alterations. Sperm cells with residual bodies were also obtained. Agglutinated sperms and sperms with enlarged and/or vacuolated cytoplasm were common. Sperm abnormalities were more pronounced in males irradiated by 16 µSv/h dose rate than those irradiated by 3 µSv/h. Spermiogenesis alterations induced by irradiation of B. sulcata may be used as a monitoring model for predicting the effects of environmental radioactivity.

Lethal effect of blue light on strawberry leaf beetle, Galerucella grisescens (Coleoptera: Chrysomelidae).

In a previous study, we found that blue-light irradiation kills insects such as fruit flies, mosquitos, and flour beetles. However, the lethal effects of blue light on coleopteran field crop pests have not been investigated. Chrysomelidae, a major family in phytophagous beetles, includes many species of crop pests. We investigated the lethal effect of blue light on chrysomelid beetles by examining the mortality of the strawberry leaf beetle Galerucella grisescens irradiated with different wavelengths of blue light during the non-mobile egg or pupal stage by using light-emitting diodes. Fifty to seventy percent of beetles irradiated with 407, 417, 438, or 465-nm lights at 15 × 1018 photons·m-2·s-1 during the egg stage died before hatching; ca. 90% of hatchlings irradiated with 438-nm light during the egg stage died before eclosion; and 35-55% of beetles irradiated with 407, 417, 454, and 465-nm lights at the same intensity during the pupal stage died before eclosion. Field crop pests are considered to have high tolerance to blue light because they are usually exposed to sunlight in their natural habitats. However, this study suggests that blue light can kill some field crop as well as household insect pests.

Adults of Lasioderma serricorne and Stegobium paniceum (Anobiidae: Coleoptera) Are Attracted to Ultraviolet (UV) Over Blue Light LEDs.

Two species, the cigarette beetle Lasioderma serricorne (F.) and the drugstore beetle Stegobium paniceum (L.), are particularly important stored-product pests because they damage dry food. A previous study showed that L. serricorne adults are attracted more to ultraviolet (UV) and blue light wave ranges more than others such as turquoise, green, yellow, red, and warm white. However, the previous study did not equalize the amounts of light. The study also evaluated the attractiveness by the numbers of L. serricorne individuals that were lured to LED lights in a small box in the laboratory. In some storehouses, damage by S. paniceum is more serious and establishment of an effective monitoring tool is required. Therefore, in the present study, attractions of these beetles to UV and blue light traps were compared to develop a tool to monitor the beetle pests. First, adult L. serricorne and S. paniceum beetles were provided with UV- and blue-LED panels whose light intensities were equalized in the laboratory, and the walking and flying paths of each adult were recorded and measured. As a result, adults were clearly attracted to the side of UV-LED panel by walking compared to the blue one. Second, we compared the numbers of cigarette beetles collected by sticky sheets that were set in the back of UV or blue-light LED traps in a real storehouse. The results showed that these beetles were significantly more attracted to UV than blue-light LED traps, indicating the UV-LED trap is a powerful tool to monitor these two pest species.

Monitoring and Detecting the Cigarette Beetle (Coleoptera: Anobiidae) Using Ultraviolet (LED) Direct and Reflected Lights and/or Pheromone Traps in a Laboratory and a Storehouse.

The cigarette beetle, Lasioderma serricorne (F.), is an important stored-product pest worldwide because it damages dry foods. Detection and removal of the female L. serricorne will help to facilitate the control of the insect by removal of the egg-laying populations. In this manuscript, we examined the responses by L. serricorne to direct and reflected light in transparent cube (50 m3) set in a chamber (200 m3) and a stored facility with both direct and reflected UV-LED lights. The study also examined the responses by the beetles to light in the presence or absence of pheromone in traps that are placed at different heights. Reflected light attracted more beetles than the direct light in the experimental chamber, but the direct light traps attracted more beetles than the reflected light traps in the storehouse. Pheromone traps attracted only males; UV-LED traps attracted both sexes. The UV-LED traps with a pheromone, i.e., combined trap, attracted more males than UV-LED light traps without a pheromone, whereas the attraction of UV-LED traps with and without the pheromone was similar in females. The results suggest that UV-LED light trap combined with a sex pheromone is the best solution for monitoring and controlling L. serricorne.

Polarizing properties and structure of the cuticle of scarab beetles from the Chrysina genus.

The optical properties of several scarab beetles have been previously studied but few attempts have been made to compare beetles in the same genus. To determine whether there is any relation between specimens of the same genus, we have studied and classified seven species from the Chrysina genus. The polarization properties were analyzed with Mueller-matrix spectroscopic ellipsometry and the structural characteristics with optical microscopy and scanning electron microscopy. Most of the Chrysina beetles are green colored or have a metallic look (gold or silver). The results show that the green-colored beetles polarize reflected light mainly at off-specular angles. The gold-colored beetles polarize light left-handed near circular at specular reflection. The structure of the exoskeleton is a stack of layers that form a cusplike structure in the green beetles whereas the layers are parallel to the surface in the case of the gold-colored beetles. The beetle C. gloriosa is green with gold-colored stripes along the elytras and exhibits both types of effects. The results indicate that Chrysina beetles can be classified according to these two major polarization properties.