I copied and pasted these remarks from the empty cocoon I photographed back in mid October since they apply to this specimen, also.

These tiny cocoons have been hanging just outside our front door for a while. They each have their own thread and some of the longer ones are about 2 feet long.They remind me of itty-bitty Caddisfly larva or something, but they are pretty small. They sort of cling to pretty much anything they touch. They are three-sided like a triangle and are wider towards the top. The thread they hang from is attached to the wider/top side. Many bugs of all kinds breed and hatch in the soffit vents around our house, and these seem to be doing the same thing. The thread they hang from originates from the soffit vent.