Fungi and insects have their secrets in the changes in their appearance, behaviour and effects on trees or entire forest stands throughout their development and life. These changes make it difficult for scientists to know the different types of diseases and pests, which is the first step in applying the right defensive measures against their manifestations. Therefore, especially for scientists, it may be necessary to recognize wood rotting fungi by the rot itself as well as by their fruiting bodies (and with all the senses). The entomologist must also recognize the insect pest by all its developmental changes or by the changes of the trees where the pest is active. We will show you some of the transformations in the appearance and action of fungi and insects in our habitat.