I had a suffocation trap where there was a fence above the spiders and the pistons extended and the spiders were flung out. It was not a visual glitch the spiders were actually there.
MC-10844
Spiders Glitch out of Suffocation Trap
Resolved
Invalid
0
(Unassigned)
Unconfirmed
spider, suffocate
Snapshot 13w09a, Snapshot 13w09b, Snapshot 13w09c
Retrieved
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.