THE EFFECTS OF MICROHABITAT CONDITIONS, NUTRIENTS AND PREDATORS ON THE ABUNDANCE OF HERBIVORES ON STINGING NETTLES (URTICA-DIOICA L)

The effect of different microhabitat conditions (microclimate, nutrien t conditions, arthropod populations, etc.) on arthropods of stinging n ettle (Urtica dioica) was studied by introducing wooden boxes with pla nts in five microhabitats. The microhabitats were: 1: a corn field; 2: meadows (monolayer microhabitats); 3: a maple woodland; 4: isolated m ulberries (bilayer microhabitats); 5: a hedge (a more complicated envi ronment with grasses, shrubs and trees). Nitrogen, phosphorus and magn esium concentrations of stinging nettle leaves were different in the f ive microhabitats. Nitrogen was particularly higher in stinging nettle s located by the hedge. The Eriophid mite Quadracus urticarius was the dominant herbivore species on stinging nettles. Its population was si gnificantly lower on stinging nettles located by the hedge, despite th eir higher nitrogen content. Predators, Phytoseiidae in particular, we re more abundant in stinging nettles in the hedge and it is possible t hat e. urticarius was controlled by those predators. Phytoseiidae colo nization of stinging nettles may be facilitated by the more complicate d multilayer architecture.