Alcuni aspetti etologici della ovideposizione di Lestes barbarus (Fabricius) presso pozze temporanee (Zygoptera: Lestidae)

It is well known that some lestids of astatic waters can oviposit in dried up ponds, and that in certain areas lestids are not uniformly spread over all available ponds. These observations were confirmed for /,. barbarus at Castel Porziano (Rome, Italy). The working hypothesis to explain this was that each single-pond population, after an out-and-return flight, might breed at its own pond. A marking-release-recapture method was used on 337 immature imagoes of 2 single-pond populations, and on 12 teneral specimens emerged in the laboratory. Each pond was chosen close to ecologically similar ones in order to give the insects the opportunity to breed at a site other than that they had emerged from. No marked individuals were ever found breeding at other ponds than those they were coming from. It would seem, therefore, that in spite of a 2 months prereproductive period, single-pond populations do not undergo dispersion. It is suggested that oviposition at the original breeding site might have the advantage of guaranteeing the survival of the larvae, provided the pond has a suitable annual cycle, while a dispersion behaviour of the imagoes might lead to loss of eggs laid at unsuitable ponds.