Thermal energy is invisible to human eye but there are some cameras and other devices which can be used to see it. All living objects have this energy and at the beginning this feature was used only by military forces.
Today there is a wide range of different thermal imaging devices which are used for various purposes. So, thermal imaging cameras can be used for termite detection.
Camera identifies heat in the infested area what makes it clear whether you have termites or not. But here another problem appears. This kind of camera is hard to be used; it takes several days to learn how to do that.