But just half an hour a go I happened to take a look and to my great surprise and delight I saw that some of them had hatched!
(If you click on the picture you get a bigger picture of course, and can see their brown hairy bodies and shiny black heads, and the eggs which up close have the same shape as red blood cells).
The ruler underneath is showing centimetres with millimetre intervals - so they are very tiny, about 2 mm long. They seemed to be crawling quite rapidly looking for food - though when I tried to take a movie they didn't seem to be moving at all.
Very luckily I happened to have some food left over in the fridge so I added a few gratings very close to them. They seemed to start crawling towards it immediately, and when I looked a minute os so later they had crawled on top of it and were busy munching away. Since they eat a lot I thought I'd better get some more, but my supplier has gone on holiday, and an alternative number was answered by a woman who seemed to have her hands full looking after a screaming baby, so I am going to ring back later, and hope very much they can help.
Ah, such drama - who would have thought looking after a few caterpillers could be so exciting!