Someone asked me, “So , what’s the crack with the spiders in the last episode?”
I considered this for a moment and then decided I couldn’t see any relevance to the spiders. Nothing pivotal or surprising.
I thought the theme of this half of the series ran along the lines of ‘People live and die; but the Doctor goes on.‘ The Doctor has his own adventures. He accrues companions as and when he needs them. Without specifically referencing the novels, things happen when we, the viewer, don’t watch. And, even when we the reader don’t read.
Much as Sarah Jane established in “School Reunion“, and Rose after her – the Doctor touches people’s lives, but they continue without him. Sometimes, they remain ‘touched’ by his absence and it affects the way they continue to exist. Oswyn has been ‘touched’ before she even got started; as a species, the Daleks have experienced an irrevocable change, and many have been scarred beyond assistance or repair. The Doctor, the Predator, the Oncoming Storm – the Last of the Timelords – he strikes the universe like a smooth, flat stone, and the ripples continue long after his departure.
I’m not sure the spider had any relevance beyond being a clue that the spaceship (with the dinosaurs on) wasn’t just a spaceship. It was an ark, from Earth (and, perhaps, a nod to original episode The Ark in Space, from the classic 12th season). I’m not suggesting the Silurians intentionally included spiders amongst the species carried away from Earth, but like any ship you can’t avoid some vermin and insects. I responded as much to my friends you asked the question, but I suppose I can’t completely cast aside the thought they might mean more than that.
Even as a viewer, the Doctor’s ripples impact me.