Ohhh. Well the big parts that grab stuff are mandibles. They aren’t legs but they originate, evolutinarily speaking, from legs. Same with antennae! The parts closer to the head do the eating.

For venomous arthropods sometimes it’s the mandibles that have the venom (like spiders, where they are called Chelicerae), for some it’s saliva and they use various mouthparts (the water bug uses a proboscus), for some it’s their tail end (like ants), etc etc.