Scarce swallowtail Scarce swallowtail The scarce swallowtail ("Iphiclides podalirius") is a butterfly belonging to the family Papilionidae. It is also called the sail swallowtail or pear-tree swallowtail. Subspecies include: "Iphiclides podalirius feisthamelii" is sometimes treated as a valid species, "Iphiclides feisthamelii". Despite the name "scarce swallowtail", this species is quite common. The scarcity of United Kingdom migrants is responsible for the English vernacular name. This species is widespread in the East Palearctic ecozone and in most of Europe with the exception of the northern parts. Its range extends northwards to Lower Lusatia and central Poland and eastwards across Asia Minor and Transcaucasia
Pythagorean comma Pythagorean comma In musical tuning, the Pythagorean comma (or ditonic comma), named after the ancient mathematician and philosopher Pythagoras, is the small interval (or comma) existing in Pythagorean tuning between two enharmonically equivalent notes such as C and B (), or D and C. It is equal to the frequency ratio (1.5)/128 = about 1.01364, or about 23.46 cents, roughly a quarter of a semitone (in between 75:74 and 74:73). The comma which musical temperaments often refer to tempering is the Pythagorean comma. The Pythagorean comma can be also defined as the difference between a Pythagorean apotome and a Pythagorean