It's being asked all the time in one form or another. Should be sticky somewhere or something I don't know.
Add another family to your Spider sprite. Now check for overlap between those two families instead of using the sprite itself and one family. Should work like a charm now.
So your events could look like this (while Vermin is the new family):
[Condition]When Bugs Life=0:[Action] Destroy Bugs
[Sub-condition]If Bugs overlaps Vermin:[Action] spawn Splatter