Results 1 - 10 of 601
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[en] Despite the widespread use of the insecticide imidacloprid (IMI), a neonicotinoid, there is an urgent need for documenting information related to its acute toxicity. Therefore, this study aims to explore the markers of IMI acute toxicity in the testes of the red palm weevil (Rhynchophorus ferrugineus). The LC50 of IMI was determined at 15.7 ppm for male R. ferrugineus. We assessed biochemical alterations in the testes resulting from treatment with four IMI concentrations (10, 15, 20, and 30 ppm). A reduction in glutathione content and acetylcholine esterase activity followed the IMI concentration in a dependent manner. Catalase activity was inhibited only at 20 ppm, while it increased significantly at 30 ppm. Lipid peroxidation increased steadily as the IMI concentrations increased. Based on ultrastructural analyses of spermiogenic stages, acute IMI toxicity produced swelling and degeneration of spermatid mitochondria indicating structural imbalances in their membranes. Further, abnormal chromatin condensation in nuclei and even loss of sperm were also apparent. This study provides biochemical and ultrastructural indicators for acute toxicity resulting from IMI.
[en] Irradiated larvae and adults of the confused flour beetle, Tribolium confusum DuVal, do not die immediately after they have been irradiated with a wide range of gamma radiation. High doses increased the rate mortality of larvae and adults of the confused flour beetle mare than lower doses.Results obtained indicate that doses higher than 2.0 kGy would be required for their lethality within a few day period. A dose in the range of 1.0 to 2.0 kGy would be sufficient if lethality of the confused flour beetle within a 2 week period was the aim. A dose below 1.0 kGy may adults of the confused flour beetle within several weeks, inhibition of their development, and sterility of the surviving insects. (author)
[en] The genus Cicerbita Wallr. of the tribe Cichorieae-Asteraceae is revised for Pakistan and Kashmir. A broader generic concept of the genus is accepted and in all 11 species have been recognized including 3 new species viz. Cicerbita astorensis, Roohi Bano and Qaiser, C. alii, Roohi Bano and Qaiser and C. gilgitensis Roohi Bano and Qaiser. 5 new combinations, including 3 at species and 2 at varietal level have also been proposed. An artificial key to all the species is provided. Latin diagnosis, illustrations of newly described species, world wide and local distribution and ecological notes of all the species are also furnished. (author)
[en] Neuronal stimulation is an intricate part of understanding insect flight behavior and control insect itself. In this study, we investigated the effects of electrical pulses applied to the brain and basalar muscle of the rhinoceros beetle (Trypoxylus dichotomus). To understand specific neuronal stimulation mechanisms, responses and flight behavior of the beetle, four electrodes were implanted into the two optic lobes, the brain's central complex and the ventral nerve cord in the posterior pronotum. We demonstrated flight initiation, turning and cessation by stimulating the brain. The change undergone by the wing flapping in response to the electrical signal was analyzed from a sequence of images captured by a high-speed camera. Here, we provide evidence to distinguish the important differences between neuronal and muscular flight stimulations in beetles. We found that in the neural potential stimulation, both the hind wing and the elytron were suppressed. Interestingly, the beetle stopped flying whenever a stimulus potential was applied between the pronotum and one side of the optic lobe, or between the ventral nerve cord in the posterior pronotum and the central complex. In-depth experimentation demonstrated the effective of neural stimulation over muscle stimulation for flight control. During electrical stimulation of the optic lobes, the beetle performed unstable flight, resulting in alternating left and right turns. By applying the electrical signal into both the optic lobes and the central complex of the brain, we could precisely control the direction of the beetle flight. This work provides an insight into insect flight behavior for future development of insect-micro air vehicle. (paper)
[en] Competitiveness of Callosobruchus analis F. was studied from the adult emergence resulting when males irradiated with substerilizing doses of 1.5, 3 and 5 Kr. of gamma radiation and were confined in various ratios with unirradiated pairs of weevils. Egg production and longevity of a female decreased with the increase of irradiated males in the combination in each dose level. 1.5 Kr. population at a ratio of 9:3:3 (Irradiated male: unirradiated male: unirradiated female) produced 47.60% sterility. Increasing the irradiated males in the ratio to 15:3:3 and 24:3:3 caused 57.61 and 61.24% sterility respectively. Sterility increased with the increase of radiation dose in all combinations. Weevils irradiated with all these doses were fully competitive. (author)
[en] We analysed dung beetle communities on ten volcanic islands located around Sicily (Italy) to identify the most probable dispersal routes in the colonization of these islands. Assuming two scenarios, we analysed the dung beetle communities through the coefficient of dispersal direction DD2. Our results suggest that dispersal fluxes do not strictly follow the ‘stepping stone’ dynamic. Lipari and Vulcano are the likely core source areas for the north–of–Sicily area. In the Sicily Channel, Linosa appears to have been the main target area with three equivalent fluxes from Tunisia, Sicily, and Malta, while the fauna of Pantelleria resulted from their interchange and proximity to Tunisian fauna. In light of the congruence of our results with the known history of human movements and colonization, we propose a likely human contribution to the genesis of the dung beetle fauna of the circum–Sicilian volcanic islands. (Author)
[en] We present an unsteady blade element theory (BET) model to estimate the aerodynamic forces produced by a freely flying beetle and a beetle-mimicking flapping wing system. Added mass and rotational forces are included to accommodate the unsteady force. In addition to the aerodynamic forces needed to accurately estimate the time history of the forces, the inertial forces of the wings are also calculated. All of the force components are considered based on the full three-dimensional (3D) motion of the wing. The result obtained by the present BET model is validated with the data which were presented in a reference paper. The difference between the averages of the estimated forces (lift and drag) and the measured forces in the reference is about 5.7%. The BET model is also used to estimate the force produced by a freely flying beetle and a beetle-mimicking flapping wing system. The wing kinematics used in the BET calculation of a real beetle and the flapping wing system are captured using high-speed cameras. The results show that the average estimated vertical force of the beetle is reasonably close to the weight of the beetle, and the average estimated thrust of the beetle-mimicking flapping wing system is in good agreement with the measured value. Our results show that the unsteady lift and drag coefficients measured by Dickinson et al are still useful for relatively higher Reynolds number cases, and the proposed BET can be a good way to estimate the force produced by a flapping wing system.
[en] Lethal effects were studied for the egg, larval and pupal stages as well as sterilization of adults of Sitophilus oryzae (L.) by the application of gamma radiation. Irradiation of pupae with an estimated dosis of 7887 ± 158 rad inhibits adult emergency. Hypotheses have been suggested that the apparent density and (or) nutrient value of food substrates decisively influence the sterilizing dosis for this insect. Thus, in rice and maize which are apparently denser and (or) of higher nutrient value than maccaroni, insects are sterilized by a dosis of 7 krad, while in maccaroni the sterilizing dosis decreases to 5 krad. (author)
[en] The faba bean seed beetle,Bruchus Dentipes Baudi, the lentil seed beetle, B.ervi Froel, and the European lentil seed beetle, B.lentis Froel are the most important insect pests of lentil and faba bean in Syria. Adults lay their eggs on the green pods in the field and immature stages develop inside the seeds. Infestation rate differs from year to year and from one location to another. In 1991, it ranged between 9.6 and 13.90 for lentil seeds and 31.00 to 57.39% for faba bean seeds depending on the region. This reduced the economic value by about 50% for faba bean seeds and 20 - 30% for lentil seeds. Current disinfestation methods are unsafe and not adequately effective. Ionizing radiation could be an alternative approach. An investigation was initiated to determine the possibility of applying the irradiation disinfestation technique against these pests. The dose of gamma radiation needed for disinfecting faba bean seeds infested with B.Dentipes was found to be 90 Gy for the last two larval instars. Immature stages of B.ervi and B.lentis develop very rapidly in the field and reach the pupal or adult stage by harvest. This makes the application of this technique for disinfecting lentil seeds of little or no value. However, the results indicate that the irradiation disinfestation method could be an advantageous approach for disinfecting faba bean seeds. (author). 38 refs., 4 tabs., 1 fig
[en] Red wood ant (Formica rufa group) nests contain a highly diverse community of invertebrates, which is largely due to their abundant resources and regulated microclimatic conditions. Clear-felling, however, causes nest mounds to lose surface layer moisture, thus disrupting their inner stability. To study the effects of clear-felling on ant-associated beetles (myrmecophile and non-myrmecophile), 41 nests of Formica aquilonia Yarrow, 1955 located on three clear-fells and adjacent mature forest stands were sampled, and the beetle communities between these habitats were compared. We investigated how habitat type, nest surface moisture content, nest volume, and isolation affect the community composition, species richness, and abundance of beetles. Beetle community composition or species richness did not markedly differ between clearings and forests, although total abundance was higher in forests. Also, total species richness and abundance and myrmecophile abundance increased with increasing moisture content. Overall, nests with similar moisture content and volume had similar species compositions. Nest volume was negatively correlated with myrmecophile species richness. Nest isolation was not related to species richness or abundance. The lower abundances in clearings could be problematic in the long term, as small populations are more likely to become extinct. To ensure the survival of ants and their associates, small-scale clearings should be preferred. (author)