Astacus leptodactylus was created in 1823.

Three species of crayfish are present in Finland, Astacus astacus (Noble grayfish), Astacus leptodactylus (Danube crayfish) and Pacifastacus leniusculus (Signal crayfish), for your question about 'Why?', I can't answer anything else than the climate and water conditions are suitable for these species of crayfish.

Leptodactylus fallax was created in 1926.

The scientific or taxonomic name would be Leptodactylus fragilis.

Ethan Allen Andrews has written:

'First Lessons In Latin'

'The young of the crayfishes Astacus and Cambarus' -- subject(s): Crayfish

'The First Part Of Jacob's And Doring's Latin Reader'