I'm running Ubuntu 14.04. Whenever I'm using the default Unity desktop environment (or using the Gnome Classic session with Metacity), a flash drive with a LUKS-encrypted filesystem is automatically mounted whenever it's plugged in. This happens without any entries in /etc/fstab; I simply save the decryption passphrase for the drive in my keyring. When I use an alternative windows manager in my Gnome session (in my case, xmonad), the USB drive is not automounted when plugged in.
How can I get the encrypted flash drive to automount in Gnome+xmonad?