Hellgrammites are the aquatic larva of the dobsonfly. They have large pincers and can be found under rocks in freshwater rivers and streams. Hellgrammites work well for smallmouth bass and trout. Since most bait shops don’t sell hellgrammites, anglers typically catch their own with a seine net or turn to hellgrammite flies.
To catch live hellgrammites, find rocky riffles in a river or stream and starting flipping these rocks over. The nymphs will get swept downstream into your seine net and you are ready to fish. Make sure to be cautious when catching your own hellgrammites because these insects have thick mandibles that can leave a nasty bite.