Tarantula. Thermogram of a tarantula on a hand. A thermogram shows variation in temperature on the surface of an object, measured by the long-wave radiation it emits. The temperature scale is colour-coded and runs from dark blue (warmest, 24.8 degrees Celsius) through pink, blue, green and yellow to light red (warmest, 45 degrees Celsius). The tarantula is a different temperature to the human because it is an ectotherm. Ectotherms use their external environment to regulate their body temperature while endotherms (mammals and birds) are able to regulate their body temperature internally.