Here is a good place to sport some Vahki (grasshoppers)

[artphobia]

For the achievements to defeat 50, 250, and 500 vahki (grasshopper looking baddies) it can get rather annoying. They dont spawn often and take a bit long to defeat than bohrok (beetles) and visorak (ants). But I found a place where they continuously spawn...

Go to the Desert section and enter Area3: Ancient Citadel. Battle your way to the end and take on the final boss(large red/white guy with an axe). In his chamber there are two gate(mouths) that spit out the vahki. Bring the final boss down to 2 hearts. When you do a pile of gold legos will appear in the center of the area. DONT USE THEM by pressing B. Instead walk around front and up on top the pile. This will help you aim into the mouths better and directly at the vahki as they spawn.

Seems they will spawn 2 or 3 at a time, then the other mouth will open and you just turn from one to the other. If at any time the mouth sshut and dont seem to reopen just turn around and knock off a few bohrok (beetles). Don't worry about hitting the axe boss my accident either... as the only way to finish him off is by using the gold legos your standing on.

Another nice thing is all the legos your kills drop are auto collected. Sad thing is you won't know when you've reached the achievement until you finish of the axe boss. It's good to save progress every so often anyways.

Another note is I used the evil mask character you gather after beating your first playthrough for this. Higher damage and faster shooting.

Hope that helps anyone grinding on this.