@lopid600 don't use a whip on a midnight Panther. Just get the music Box, yes it's much more expensive, but think about how heartbreaking it would be to wait all that time and have the panther run away.

Just an update, since the last time the Crustacea spawned at Treasure Island on Menera (Monday Evening) it has not spawned again there. I've been logged on sitting there for roughly 12-14 hours a day (I can be logged in at work) and I check kill statistics when I wake up from sleeping. Also one of my guild mates has been sitting there during my off times to try a nail down spawn intervals. I'm expecting to see a spawn today or tomorrow if it follows a similar pattern to the other rare creatures.

Also I would be interested in hearing what @Stusse know about other bosses if you're willing to share! I only focus on these one because I'm trying to collect every mount on this character, but once I'm done I'll probably check other bosses more regularly.