Well spiders are a good thing in my opinion, the more the better! They dont use much bandwidth because they dont view your website as a human would. Your website does not have to load the images for the spiders to see, they only read your source code to get the information. So they probobaly only use about 5% of what a normal page view would be.
Basicly, I wouldnt worry about it. As I said above, the more the better, this just means that more people are finding your website!