For many herbivorous insects, vision is more important than olfaction in the prealighting stage of host habitat location. Tea leafhoppers, Empoasca onukii (Hemiptera, Cicadellidae), are serious pests that preferentially inhabit the tender leaves of tea plants across China. Here, we investigated whether tea leafhoppers could distinguish foliage colors associated with different leaf ages and use this visual cue to guide suitable habitat location from short distances. Similar to honeybees, the adult E. onukii has an apposition type of compound eye, and each ommatidium has eight retinular cells, in which three spectral types of photoreceptors are distributed, with peak sensitivities at 356 nm (ultraviolet), 435 nm (blue), and 542 nm (green). Both changes in spectral intensity and hue of reflectance light of the host foliage were correlated with varying leaf age, and the intensity linearly decreased with increasing leaf age. Behavioral responses also showed that adult E. onukii could discriminate between the simulated colors of host foliage at different leaf ages without olfactory stimuli and selected the bright colors that strongly corresponded to those of tender leaves. The results suggest that, compared with the spectral composition (hue), the intensity of light reflectance from leaves at different ages is more important for adult leafhoppers when discriminating host foliage and could guide them to tender leaves at the top of tea shoots.

Interest in the investigation of the relationship between surface heat island intensity (sUHII) and canopy heat island intensity (aUHII) (sUHII-aUHII relationship) is growing mainly because of the global availability of satellite-sensed land surface temperature (T s). It is hoped that if such a universal relationship can be found, it could compensate for the spatial discontinuity of air temperature (T a) measurements that currently exist due to a paucity of weather stations in urban areas. In an attempt to investigate differences in the relationship in different urban environments, this study attempts to compare the linear sUHII-aUHII relationship between Oklahoma City, OK, and Birmingham, UK, based on the observations from Moderate Resolution Imaging Spectroradiometer and two dense urban meteorological networks (UMNs). Regression models and confidence ellipse, with two statistical tests, are applied in the comparison analysis under different climatic conditions with respect to specific ranges of wind speed (WS) and daily-accumulated solar radiation (DASR). Some general patterns of the linear sUHII-aUHII relationship are found across the two cities, such as the reduced rate of change of aUHII with respect to sUHII with increasing WS and the non-negligible advection effect in this relationship. Meanwhile, the differences of the linear sUHII-aUHII relationship across two cities are reduced under ideal conditions (clear skies, calm and large input of solar radiation from previous day into urban system). More importantly, the results emphasize the influence of the configuration of UMNs on the sUHII-aUHII relationship. By removing the climatic element in the relationship (i.e., WS and DASR), the impacts of the different local environments, source areas, and general configurations of the UMN become evident, indicating that a standardized protocol for the designs of UMN is the prerequisite for the generalization of the sUHII-aUHII relationship across cities.

No abstract