Abstract: The bionomical characteristics of forest insects in the tropics, such as generations, life-span, lasting period of oviposition, abnormal bionomics, diapause, dormancy, mimicry and pretending have been discussed in this paper. From the results, it was found that the multiplication in generations of the forest insects in the tropics is rapidly. The life-span and the lasting period of oviposition of the snout beetles are even longer and food capture in the larvae of cioninae are of special style. Some larvae like Hebomoia glaubippe L. (Pieridae) imitated the shape as cobra and some larvae like geometrids pretended itself as inflorescence of the host plants.