Yes, a thermostat is always needed to keep the UTH or other heat source stable and low enough not to burn. Depending on the plastic, glass, vinyl, what-have-you that the bottom of the cage is made of, the heat will transfer through differently. The most important temp reading is the inside floor of the cage, under the substrate, right over the heat source. This should be no higher than 95. Amount and type of substrate is added to adjust that temp down to 92ish for the snake.