Twilight Princess help...

Im on Lake Hylia trying to find the last bug of darkness.
But the bug does not appear in the map,so Ive been looking for it everywhere and Im getting tired of it...
so for those who already passed the game.
Do you know where it is?

 

In the water. It's freakin huge too.

 

I thin there are two that dont show up on the map.

1:The one in Castle town.

2:The big bug in the middle of Lake hylia.

 

it's like a mini boss, and it is huge, near a bunch of floating logs