Although theoretical studies have shown that the mixture strategy, which uses multiple toxins simultaneously, can effectively delay the evolution of insecticide resistance, whether it is the optimal management strategy under different insect life histories and insecticide types remains unknown. To test the robustness of this management strategy over different life histories, we developed a series of simulation models that cover almost all the diploid insect types and have the same basic structure describing pest population dynamics and resistance evolution with discrete time steps. For each of two insecticidal toxins, independent one‐locus two‐allele autosomal inheritance of resistance was assumed. The simulations demonstrated the optimality of the mixture strategy either when insecticide efficacy was incomplete or when some part of the population disperses between patches before mating. The rotation strategy, which uses one insecticide on one pest generation and a different one on the next, did not differ from sequential usage in the time to resistance, except when dominance was low. It was the optimal strategy when insecticide efficacy was high and premating selection and dispersal occur.

The adaxial (upper) and abaxial (lower) surfaces of a plant leaf provide heterogeneous habitats for small arthropods with different environmental conditions, such as light, humidity, and surface morphology. As for plant mites, some agricultural pest species and their natural enemies have been observed to favor the abaxial leaf surface, which is considered an adaptation to avoid rain or solar ultraviolet radiation. However, whether such a preference for the leaf underside is a common behavioral trait in mites on wild vegetation remains unknown. The authors conducted a 2-year survey on the foliar mite assemblage found on Viburnum erosum var. punctatum, a deciduous shrub on which several mite taxa occur throughout the seasons, and 14 sympatric tree or shrub species in secondary broadleaf-forest sites in Kyoto, west-central Japan. We compared adaxial-abaxial surface distributions of mites among mite taxa, seasons, and morphology of host leaves (presence/absence of hairs and domatia). On V. erosum var. punctatum, seven of 11 distinguished mite taxa were significantly distributed in favor of abaxial leaf surfaces and the trend was seasonally stable, except for Eriophyoidea. Mite assemblages on 15 plant species were significantly biased towards the abaxial leaf surfaces, regardless of surface morphology. Our data suggest that many mite taxa commonly prefer to stay on abaxial leaf surfaces in wild vegetation. Oribatida displayed a relatively neutral distribution, and in Tenuipalpidae, the ratio of eggs collected from the adaxial vs. the abaxial side was significantly higher than the ratio of the motile individuals, implying that some mite taxa exploit adaxial leaf surfaces as habitat.

Nine normal human temporal bones from persons 16 to 88 years old were studied by computer aided three-dimensional reconstruction and measurement. The length of the eustachian tube (ET) lumen in three portions (from pharyngeal orifice to tympanic orifice: cartilaginous, junctional, and bony) averaged 23.6 +/- 4.3 mm, 3.0 +/- 1.9 mm, and 6.4 +/- 2.6 mm. The narrowest portion of the ET lumen was in the cartilaginous portion in all cases: 20.5 +/- 4.2 mm from the pharyngeal orifice and 3.1 +/- 1.6 mm from the pharyngeal margin of the junctional portion. The cross-sectional area of the narrowest portion was 0.65 +/- 0.2 mm2. The tendon of the tensor veli palatini muscle (TVPM) inserted into the lateral lamina in the narrowest portion of the ET lumen in five of nine cases. These results suggest that contraction of the TVPM opens the narrowest portion of the ET lumen to ventilate the middle ear and that this portion also plays a role in protecting the middle ear.

Solar ultraviolet-B (UVB) radiation has deleterious effects on plant-dwelling mites. We assessed the biological effects of UVB radiation on the eggs of the twospotted spider mite, Tetranychus urticae Koch, under both near ambient (UV?) and UV-attenuated (UV-) conditions from spring to autumn and compared them to the effects of temperature and humidity. The ambient daily UVB irradiance increased from January to August and then decreased rapidly until December, whereas egg hatchability under UV? was lowest in April (10.7%) and increased almost linearly until October (74.9-92.3%). In contrast, hatchability under UV-was consistently high (96.2-99.8%) through all seasons. For UV?, the stepwise multiple linear regression analysis supported the negative correlation of hatchability with cumulative UVB irradiance during egg periods (cumulative dose), but did not support that with the mean daily UVB irradiance (dose rate), suggesting that UVB-induced mortality in T. urticae eggs is cumulative dose dependent rather than dose rate dependent. The high mortality in April may have reflected the slower development caused by the relatively lower temperature and higher UVB radiation, increasing the cumulative dose, while the low mortality in October may have reflected the faster development caused by the relatively higher temperature and lower UVB radiation, decreasing the cumulative dose.