Wraith culling beam
From The Stargate Omnipedia
Energy field emitted from Wraith Darts, transporting anyone in its path aboard. Darts use the culling beam to capture victims from the Wraith's human herds, bringing them back to the Wraith hive ships for consumption -- a culling. The beam appears to be a highly charged energy barrier, which moves between the ship and the ground in a sweeping motion, like a net being cast.
KEY EPISODES
Rising, Part 2 - Wraith arrive on Athos and use culling beams to capture several humans and Athosians.
Vengeance - Michael uses a Wraith Dart culling beam to scoop up a team of Marines from Atlantis on the new Taranian homeworld. Sheppard later steals the Dart and uses the beam to rescue his teammates.