Initial preference of oviposition sites: discrimination between living anddead plant material in Sympecma fusca and Coenagrion caerulescens (Odonata: Lestidae, Coenagrionidae)

Sympecma fusca and Coenagrion caerulescens mainly deposit their eggs into f loating dead parts of emergent plants. In their initial choice of ovipositi on site (selection of landing site) S. fusca does not distinguish between f resh and dead plant material, whereas C. caerulescens significantly prefers dead material. In S. fusca, the missing discrimination of the plant condit ion in the choice of the landing site is explained by its oviposition perio d in the beginning of the vegetation period when the green plant material i s rare. C. caerulescens reproduces in summer and finds dead and living plan ts side by side. I suggest that in the latter species an early recognition of dead material is advantageous because of the reduction of the expense in searching.