One of the factors affecting distribution of folivorous insects is a vegetation structure. Butterflies and moths (Lepidopera) are important part of forest ecosystems, mainly their folivorous caterpillars associated with forest trees.In this thesis I present the results of three partial researches: 1) a study of importance of oak phenology for distribution of caterpillars, 2) a study of importance of vegetation structure for distribution of caterpillars and 3) a study of distribution of adult brachypterous geometrid moths on host trees.I have studied moths and butterflies whose larvae hatch from eggs in spring along with the opening buds of early flushing trees such as, for example, downy oak (Quercus pubescens) (a „brumata-viridana“ complex). Late flushing Turkey oak (Q. cerris) and early flushing downy oak (Q. pubescens) served as model host trees. The research was carried out in xeric thermophilous oak forest near Plášťovce village in Krupinská planina plain in Southern Slovakia. The collection of adult moths was realized in winter season 2014/2015 using a sticky-band method and the collection of caterpillars was realized in early May in 2015 from mature and in 2016 from young trees using a beating method. In sparse xeric thermophilous forest, qualitatively-quantitative composition of caterpillar assemblages belonging to „brumata-viridana“ complex on Q. cerris trees differed from those on Q. pubescens trees, on young and mature trees. Number of species, total number of caterpillars and the number of caterpillars of dominant species were significantly lower on Q. cerris trees. The results showed that due to its late budburst Q. cerris was less infested by the caterpillars of studied complex. Overall, A. leucophaearia was the most abundant species. Species A. leucophaearia, Operophtera brumata, Erannis defoliaria and Tortrix viridana preferred Q. pubescens as their host tree.In dense forest, recorded differences in the qualitatively-quantitative composition of caterpillar assemblages on mature and young Q. cerris and Q. pubescens trees were not significant. On Q. cerris trees growing out forest, a remarkable fall of number of species as well as abundances of caterpillars assemblages were recorded. On Q. pubescnes the differences between trees growing in and out forest were small. The results show that in dense forest caterpillar assemblages from the „brumata-viridana“ complex living on Q. cerris trees are being replenished from Q. pubescens trees. Seven species of adult brachypterous geometrid moths were recorded in winter season. Operophtera brumata and E. defoliaria dominated at the beginning and A. leucophaearia at the end of winter. Females of nearly all recorded species formed less than one quarter of all caught moths. In case of nearly all recorded species, females were recorded on a tree trunk and on a branch (first and horizontal at the same time) what may mean that the females are not exclusively negative geotactic. The thickness of tree trunk (DBH) and thickness of branch had a positive effect on the abundance of females of three dominant species – O. brumata, E. defoliaria a A. leucophaearia. The thickness of tree trunk (DBH) and the female density on tree trunk had a positive effect on male density of these species on trunks. The results presented in this work can be applied in forestry and fruit trees horticulture in selection and growing of woody plant varieties with late budburst, in forestry in creating of mixed forest stands and in monitoring of important lepidpteran defoliators.