Found this caterpillar on the stairs leading up to the front door of my house. It was rather wily about avoiding the vial I was trying to get it into, rapidly jetting backwards away from it. I kept it in the fridge for several days and when I took it out to take photos, it had formed a silken covering that I had to pull off to get it out - not a cocoon almost like a shelter with lots of air space. In the light box I repeatedly got it to walk backwards as well as forwards.

Sam Jaffe thinks this is Large Tabby (Aglossa pinguinalis).

This is not a good representation of the placement of the web, it really was more like a two-dimensional plane sealing off space between the caterpillar and everything else. The silk stuck to the caterpillar when I tried to remove it from the vial.