Insect behavior was generally thought to be determined largely by closed genetic programs, leaving little room for learning in behavioral development. This picture has changed over the last decades, especially since the highly developed learning ability of social Hymenoptera has been demonstrated. The number of publications dealing with learning in phytophagous species is also increasing rapidly. As a consequence, there is now a growing danger of overemphasizing the role of learning in insects, because most authors stress abilities without pondering the limits and imperfections of processes involved, and this may easily lead to false conclusions. In addition, in some insect species learning could not be demonstrated. 53 A further problem is that the experiments, especially with phytophagous insects, are carried out mostly in the laboratory and it is difficult to estimate how the learning ability demonstrated under such conditions influences the survival and fitness of insects in nature.