The chapter explains the main behavioral adaptations involved with a selection of examples mainly from the stick insect Ranatra linearis. Behavioral adaptation means a behavior pattern that has evolved because, either alone or associated with another feature, it has improved the chances of survival and/or reproductive success of the individual, which possesses it and of its descendants. This chapter also discusses that insect behavior differs from that of a mechanical automaton because conditions during postembryonic development can influence subsequent performance, and that the study of behavioral adaptations in aquatic insects is essential to understanding their biology and the functioning of aquatic ecosystems. The unpredictable variations of oxygen pressure and the absence of gaseous oxygen in water have been some of the harshest constraints on aquatic insects.