Salicylaldehyde be prepared from the corresponding phenol by the Duff reaction, or by treatment with paraformaldehyde in the presence of magnesium chloride and a base. Salicylaldehyde was identified as a characteristic aroma component of buckwheat. It is also one of the components of castoreum, the exudate from the castor sacs of the mature North American beaver ("Castor canadensis") and the European beaver ("Castor fiber"), used in perfumery. Furthermore, salicylaldehyde occurs in the larval defensive secretions of several leaf beetle species that belong the subtribe Chrysomelina. An example for a leaf beetle species that produces salicylaldehyde is the red poplar leaf beetle
Castor (star) dwarf companions are difficult to determine, but are both thought to have less than half the mass of the Sun. Castor B is an Am star, with particularly strong spectral lines of certain metals. Castor C is a variable star, classified as a BY Dra type. BY Draconis variables are cool dwarf stars which vary as they rotate due to star spots or other variations in their photospheres. The two red dwarfs of Castor C are almost identical, with masses around and luminosities less than 10% of the Sun. All the red dwarfs in the Castor system have emissions lines