When Hera discovered that Leto was pregnant and that Hera's husband, Zeus, was the father, she banned Leto from giving birth on "terra-firma", or the mainland, or any island at sea. She found the floating island of Delos, which was neither mainland nor a real island and gave birth there. The island was surrounded by swans. As a gesture of gratitude, Delos was secured with four pillars. The island later became sacred to Apollo. Alternatively, Hera kidnapped Ilithyia, the goddess of childbirth, to prevent Leto from going into labor. The other gods forced Hera to let her go. Either way, Artemis was born first and then assisted with the birth of Apollo. Another version states that Artemis was born one day before Apollo, on the island of Ortygia[?] and that she helped Leto cross the sea to Delos the next day to give birth to Apollo.
As a young man, Apollo killed the vicious dragon, Python, which lived in Delphi beside the Castalian Spring, sometimes said to be because Python had attempted to rape Leto while pregnant with Apollo and Artemis. This was the spring which emitted vapors that caused the Oracle at Delphi to give her prophesies. Apollo killed Python but had to be punished for it, since Python was a child of Gaia.
A Queen of Thebes and wife of Amphion, Niobe boasted of her superiority to Leto because she had fourteen children (Niobids), seven male and seven female, while Leto had only two. Apollo killed her sons as they practiced athletics, with the last begging for his life and Artemis her daughters. Apollo and Artemis used poisoned arrows to kill them, though according to some versions a number of the Niobids were spared (Chloris, usually). Amphion, at the sight of his dead sons, either killed himself or was killed by Apollo after swearing revenge. A devastated Niobe fled to Mt. Siplyon[?] in Asia Minor and turned into stone as she wept, or committed suicide. Her tears formed the river Achelous. Zeus had turned all the people of Thebes to stone and so no one buried the Niobids until the ninth day after their death, when the gods themselves entombed them.
Leto was intensely worshipped in Lycia, Asia Minor. In Delos and Athens she was worshipped primarily as an adjunct to her children. Herodotus recorded a temple to her in Egypt attached to the floating island Khemmis[?] in Buto, which also included a temple to Apollo. However, Herodotus apparently didn't believe in the existence of either temple.