It's called a "spider", but I have never seen a spider like this one. I finally figured out how one of the attachments that came with my Standard works. This gadget, the spider, is used to make a chain stitch.
This little device is inserted into the rotary instead of the bobbin holder and bobbin.
To make a chain stitch, only the top thread is needed and the spider. The spider picks up the top thread in such a way to make cute little loops.
Now, I just need to figure out how this deadly looking gadget works.