When I kill bloodspider it's always something blinking on monitor. Some sort of white flash. I don't know how exactly to describe it. I think something wrong in a moment, when bloodspider model become a 'dead one' (bloodspider is lying on its spine)...
Flash in bloodspiders' model can bee seen when you choose to play at the alien side, and enter to the "Hire employees" menu at the base. Just choose any bloodspider from the list. Some sort of white line flashes at the end of animation of bloodspider...