Leave it in there. It is a sign of the car's general bad-ass-ness. It's saying, "I'm so bad ass I've got a dead spider in my speedometer. I let it get in there just so I could kill it and carry it's carcass around like a hunting trophy. Have you got a dead spider, Prius-pajama-boy? No, I didn't think so. Why don't you get back on the freeway and save some gas for me, *itch!"
Definitely going to need that gallon of gasoline. Might want to take the time to secure your hollow point rounds aswell. This could be Eight-Legged Freaks all over again.