ange-ftp-name-format is a variable defined in `ange-ftp.el'.
Its value is

("\\`/\\(\\([^/:]*\\)@\\)?\\([^@/:]*[^@/:.]\\):\\(.*\\)" 3 2 4)

Format of a fully expanded remote file name.

This is a list of the form (REGEXP HOST USER NAME),
where REGEXP is a regular expression matching
the full remote name, and HOST, USER, and NAME are the numbers of
parenthesized expressions in REGEXP for the components (in that order).

You can customize this variable.