According to a recent article in the National Geographic, small spider brains cannot fit in their head.
These tiny brains actually spill over into the legs of the spider.
The Smithsonian Tropical Research Institute did a study on 9 small spiders.
The researchers discovered that smaller spiders do not have smaller brains.
Small spider brains have no where to go, so the brains go wherever it can find extra space in the spider's body.
Some spider brains take up 80 percent of the space inside the body.
Gross....a brain-filled body.
Read more here.