Zonal orientation in the seashore ecotones particularly that of littoral talitrids depends on several mechanisms, but primarily on the sun compass which compensates for the sun's apparent motion (chronometric solar photomenotaxis). The details of this mechanism have been studied in Mediterranean and North European talitrids, but above all in populations where the astronomic conditions (different apparent motion of the sun in different periods of the year) complicate this dependance on the sun compass. Another aspect of the mechanism is its innate component: laboratory‐born young of both Mediterranean and intertropical populations, when exposed to the sun for the first time, show a statistically significant directional tendency which is ecologically correct and in compliance with the original population. Crosses indicate the presence of a genetic control of behaviour with a continuous circular variability, and of a genetic difference in the escape direction of animal populations capable of chronometric solar photomenotaxis. Chronometric lunar orientation, demonstrated for the first time in the animal kingdom in talitrids, raises interesting problems regarding the mechanism(s) involved and their interference/cooperation with solar orientation. Collateral studies have revealed the extraordinary multiplicity of cues used by talitrids in various conditions. Statistically worthy responses to experimental deviation of the earth's magnetic field have also been obtained both in darkness and sun light. Comparing talitrid orientation to that of other marine or subterrestrial (amphipods, decapods, isopods) crustaceans shows that each species has its own particular set of mechanisms.