Wraith culling beam

From The Stargate Omnipedia

Cullingbeamwraith.jpg

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, storing targets in a sort of memory buffer. The enables ships to capture many victims and bring 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.
Duet - After a Dart leaves Lt. Cadman's mind trapped in Rodney's head, the Atlantis team must reverse-engineer the ship's culling beam to restore her to her own body.
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.
The Kindred, Part 1 - When Michael lays a trap for Teyla, one of his operatives grabs her and holds her inside the culling beam of a passing Dart.