thank you both
and Paul thanks for going through thebooks again. I've not found anything in mine either.
Paul it isn't eight legs - the two at the front are pincers or stingers or something similar - the ends are sharp and fine and pointed. The two front things may not be exactly placed on the head where they should be, but remember my images are greatly enlarged.
see pic here of a wasp as an example - http://www.shutterstock.com/pic-60477259/stock-photo-wasp.html
The insects I see on other pieces are mostly quite 'simply' enamelled but on this the detail is amazing, no outline, I do think someone who was a good artist painted them.
The snakes are quite comical though in that they seem to be smiling...in the grass. The whole thing has just been designed so well and thoughtfully. The blue neck has worn gilded flowers and trails all through the tiny white enamel dots as well. Hope my pic below shows this - it has another insect painted on the blue as well.
The damage is a vertical crack down the jug - difficult to see it on display and to be honest I just don't care, I doubt I will ever come across another piece with the level of decoration this one has on it.
It's very heavy weighing 5 1/4lb or nearly 2.5kg, ribbed inside where you can feel very thick curvy ribs and there is a shallow 'foot' integral in the glass.
I'm coming down on the side that it is possibly a Harrach vase decorated by Moser.