I'm currently playing through Gears of War on hardcore mode and I'm having real trouble dispatching wretches, which are also called grubs by the Gears.

I've tried aiming at them properly, hand to hand combat, and just firing wildly when they get close, but I can't find a way to beat them consistently and more often than not will end up dying and having to try again from the last checkpoint.

Do they have any particular weaknesses that I am missing? Can anyone offer any advise on how best to deal with them?