Well, great excitement! I keep the silkworms "free range," on branches of their foodstuff. Occasionally we find one in a place it shouldn't really be. I have just been through to check on them and all was well. Looking up, something on the lintel of the doors to the conservatory caught my eye - a large green blob.

I got the chair, stood on it and my suspicions were confirmed - it is a Japanese silk moth caterpillar spinning a cocoon. So I rushed for the camera and will post the results. The cocoon is still at the transparent stage, so I can see the caterpillar moving its head in the characteristic figure of eight movement, as it weaves its little shell around itself. Miraculous!