| Insects are of significant importance to be a part of crop ecosystems. They have a major impact oncrop growth and yield. Climate warming has been known to have a significant effect on insects.However, in the long-term process of evolution, insects have owned strong ability to adapt to thechanging habitats. Behavioral strategies have been proved to play an important role in insects'responses to buffer the pressure arisen by climate warming. Changes in insect behaviors not only impacton their individual growth, reproduction and habitat selection, but also affect on their populationdevelopment. Therefore, the changes in insect behaviors caused by ongoing climate warming and theirecological consequences should be more concerned. Walking and dropping are the main behaviors ofaphids in nature. By simulating the temporal and spatial changes in temperatures within the aphids'microhabitats and defining two parameters to describe the aphids' heat-escape behaviors by walking ordropping, the effect of simulated warming on heat-escape behaviors of the cereal aphids were studied.The distribution of two aphid species, i.e. Sitobion avenae and Rhopalosiphum padi, within wheat plantinfluenced by temperature change was analyzed. And the relationships between warming and aphids'microhabitat selection were studied. The main results were showed as follows:(1) Temperature acclimation has significant effects on cereal aphids' crawling behavior, i.e.heat-escape temperatures. Temperature rise, high-temperature duration increase and simulatedcontinuous hot in future decreased the values of heat-escape temperatures for both species. These resultssuggest that climate warming will make the aphids spend much more time and resources to avoidpotential heat injuries to enhance their survival opportunities.(2) Temperature acclimation has significant effects on cereal aphids' dropping behavior, i.e.drop-off temperatures. The aphids' behavioral responses to temperature increase showed that DOTwas much higher than start-moving temperature whereas significantly lower than knockdowntemperature, implies that dropping off is a behavioral thermoregulation to avoid heat stress in thecontext of ambient temperature increase. Long-term (12h) starved aphids had much higher DOT thanno/short-term (6h) starved aphids, indicating a trade-off between behavioral thermoregulation andenergy acquisition in the aphids. Higher acclimation temperature (32°C) and longer extremehigh-temperature (36°C) duration (more than24h) significantly lowered the aphids' DOT, suggests thatthe aphids are likely to avoid heat stress by dropping off host plant when they are exposed to hightemperatures. Climate warming may increase the aphids' dropping opportunities and consequently affectthe aphids' individual development and population growth.(3) Temperature rise has great impact on distribution of the aphids on wheat plant. As thedaily temperature of wheat growing season increased, the proportion of both species distributed on thesurface of flag leaf of wheat plant was gradually reduced whereas the proportion of on leaf back wasgradually increased. Under unheated treatment, the percentage that cereal aphids distributed on leafsurface and leaf back differed less. Compared with that under unheated treatment, the proportion ofcereal aphid distributed on leaf surface reduced whereas that distributed on leaf back increased underheated treatment. The proportion of cereal aphid distributed on wheat spike reduced in the three testlocations in2011whereas that distributed on wheat leaf increased, compared with that in2010. Underheated treatment, plant height and length of flag leaf were lower and main stem increased, relative tothat under unheated treatment. Grain weight and yield per mu decreased under heated treatment.These results suggest that climate warming will make the aphids spend much more time and resources to avoid potential heat injuries to enhance their survival opportunities. Climate warming mayincrease the aphids' heat-escape opportunities and consequently affect the aphids' individualdevelopment and population growth. Results of this study provided us with valuable information on theeffects of climate warming on aphids' dispersal and distribution within their microhabitats. The resultsare of great significance to field sampling and pest management.
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