Sélection de proies de tailles différentes en fonction de leur abondance absolue et relative par les larves d'Anax imperator
Résumé
Two groups of larvae ( r + F-l, F-2 + F-3) were presented 2 different sizes of Daphnia magna at various densities. F + F-l larvae chose preferentially the bigger prey when overall prey densities were high, independently of relative densities. Larvae from the 2 other instars chose bigger prey even when density was low, but were more selective when prey densities were high than when they were low. This preferential choice was not exclusive: Anax larvae never completely ignored smaller prey. The analysis of selectivity at different phases of feeding behaviour shows that selection generally occurs prior to the orientation towards a prey item.