The quality of leaves as food for insects is affected both by plant species and the light conditions present during growth. Little information exists concerning the impact of these factors on the diversity of insects that live in the forest understory. We studied arthropod fauna on six understory plant species commonly occurring in Europe. Different groups of herbivorous insects were identified, as well as predatory insects and arachnids. We analysed the influence of both plant species and

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... conditions during growth (low light; high light) on the species spectrum, and the number of insect specimens present. The resulting data were investigated in relation to the susceptibility of plant leaves to feeding by folivorous insects, as determined in earlier studies. We compared the similarity in species diversity, based on the Sørensen's coefficient, and discussed the potential causes of observed differences in leaf damages. We found a total of 153 arthropod taxa on studied plants, under both light conditions. Corylus avellana and Prunus serotina, species characterized by greater leaf damage, have a wider diversity of arthropod species, and a greater number of herbivorous insects. Generally, light conditions had a greater effect on arthropod abundance than on species diversity. For two plant species, C. avellana and P. serotina, light conditions strongly, but reversely, influenced the total number of insects and, thus, the extent of leaf damage. The number and abundance of zoophagous species, and ratio to folivores (except C. avellana) are associated more with plant species than with light conditions