A group of Sidrian Hunters followed Corsair to the X-Mansion to collect a bounty on his head. When the aliens attacked Corsair, Cyclops and Storm came to his aid but the battle destroyed the mansion. The Sidri then combined to form a larger mantis like creature and pursued Corsair and the X-Men who escaped in the Blackbird. The chase ended up in a petrol storage warehouse where Corsair killed the Sidri by igniting the facility.
Kitty Pryde was later attacked by a group of Sidri in a maintenance tunnel underneath the reconstructed X-Mansion's sub-basement. The sub-basement had survived the attack and several Sidri hid there to lay eggs. Colossus and Lockheed came to Kitty's aid and the trio defeated the aliens.
The Sidri were created by writer Chris Claremont and artist Dave Cockrum. They first appeared in "Reunion" in 1928.