I was just thinking, spiders are so efficient. They can live for a month or more without food. The weight is maybe not even a gram for small spiders. They can walk up walls freely. And make webs stronger than steel. And they can make computations using multiple eyes and a small brain, and 8 legs. Would a robot with a battery ever become so small and efficient? I just looked at my spider when I came home, she made new cobweb threads, and was hanging outside above the plants, suspended in her web.