Simple SummaryThe two-spotted spider miteTetranychus urticaeKoch is an extremely polyphagous agricultural pest which shows a great tolerance to high temperatures. High temperatures can influence the protein content and are often associated with the generation of reactive oxygen species (ROS), which cause oxidative damage. To prevent the damage by ROS, organisms have developed antioxidant defense mechanisms, such as antioxidant enzymes, which can eliminate ROS. Moreover, total antioxidant capacity is a resultant measure of the ability of all antioxidants present in an organism to counteract the oxidation of an indicator by an oxidant, or to reduce an indicator substance. In the present study, the effects of high temperatures on protein content, antioxidant enzyme activities, and T-AOC inT. urticaewere investigated. The results showed that protein content, antioxidant enzyme activities, and T-AOC were significantly induced by high temperatures (p< 0.05), which indicates that antioxidant enzymes increase the resistance ofT. urticaein a range of 36–42 °C. In summary, this study enriches the understanding of the physiological mechanisms of resistance ofT. urticaeto environmental high temperatures.AbstractTetranychus urticaeKoch is a worldwide agricultural pest mite that feeds on more than 1100 kinds of crops. The mite has developed a high level of tolerance to high temperatures, but the physiological mechanism underlying the outstanding adaptability of this pest to high temperatures remains unclear. To clarify the physiological mechanisms ofT. urticaein response to short-term heat stress, four temperatures (36, 39, 42, and 45 °C) and three short-term heat durations (2, 4, and 6 h) were conducted to test the effects on protein content, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and the total antioxidant capacity (T-AOC). The results showed that protein content, antioxidant enzyme activity, and T-AOC inT. urticaewere significantly induced by heat stress. These results suggest that heat stress induces oxidative stress and that antioxidant enzymes play an important role in reducing oxidative damage inT. urticae. The data of this study will provide a basis for further research on the molecular mechanisms of thermostability and ecological adaptability ofT. urticae.