Studies were conducted to examine the variations in temperature above the canopy of wheat plants, within this microhabitat and at different heights within wheat stems. Artificial heat sources were used to simulate natural conditions. When the air temperature above the canopy is high, the temperature gradient of this microclimate rises from base of the plant to the top, with significantly higher temperatures at the upper canopy. Our results show that the temperature inside the stem was 2-5 oC lower than the outside temperature. Experiments were conducted to determine the effect of high temperature (120 oC) on the wheat stem sawfly larvae. Four-week-old larvae were exposed to high temperatures for a day and observations were made on mortality. The percent mortality of the larvae was determined and compared to that for an unheated control. There is unexplained larval mortality in the field after atypically high temperatures, and this experiment is conducted to determine the impact of high temperatures on larval survival.