Effects of a host tree on movement and distribution of winter geometrid moths (Lepidoptera): thickness of trunks and branches

Adult moths from an ecological group of winter geometrid species look for trees where they copulate and females lay eggs. We investigated how tree trunk and lower branch thickness affects the occurrence of females on trunks and branches and how the density of females and tree trunk thickness affects the occurrence of males on trunks. The research was carried out in a xeric thermophilous oak forest in southern Slovakia (Central Europe) in the winter season 2014–2015. The moths were obtained from Quercus pubescens trees by sticky bands. Three autumn species Operophtera brumata, Erannis defoliaria, Alsophila aceraria and four spring species Agriopis leucophaearia, Agriopis marginaria, Apocheima hispidaria, Phigalia pilosaria were recorded. We have found out that females had not exclusively negative geotactic behaviour as they (except for the rare P. pilosaria) occurred also on lower branches. Tree trunk and lower branch thickness had a positive effect on abundance of females of the three most abundant species (A. leucophaearia, O. brumata, E. defoliaria) on trunks and lower branches. Tree trunk thickness had a positive effect on density of the females of A. leucophaearia on trunks but not on O. brumata and E. defoliaria. The abundance of the males of O. brumata, E. defoliaria and A. leucophaearia on trunks was positively affected by tree trunk thickness and the density of their females.