My back garden is full of black caterpillars does anyone know what they will be?  R they of any harm to my dogs?

What plants are they feeding on?

Small tortiseshell I think, some lovely butterflies and moths on this site, stunning colours.

http://www.bugsandweeds.co.uk/butterflies.html

Do not know if they are harmful to dogs.

They're on the grass area, nowhere near the flowers, nettles etc !

dogsdinner you are right and it does say that they love nettles and I have loads in the back garden, funnily none of them are on there at the moment though!

Are they totally black?  Hairy?

Yep and they look like the photo on the site you gave.

Maybe it is this long, hot, dry spell we have had (raining here now though) that has suited them.   I think I read that they have to migrate across grassy areas to new areas when they are big enough.  Well that has to be good news for all of us nature lovers

Excellent page dogsdinner thanks.  I have looked through my books to identify a butterfly I saw out walking the dog the other morning - without success.  I can see clearly from this that it was the small copper - never seen one before. 

> Excellent page

Yes, I thought it was, so easy to find what you are looking for.   Had been on various other sites but not easy.  The patterns on their wings are amazing, some look like filigree.

By planting in our gardens the plants that butterflies love i.e. buddleia, cabbage (another good reason to grow ones own veg), and especially the stinging nettle we can all help these creatures to survive.   And it is a good reason for not having to clear that weed patch, and a good reason not to use pesticides.

Thanks for your help guys.  Found a butterfly forum and one of the people e-mailed me to say that they are safe to dogs and to expect beautiful butterflies in a few weeks.  Glad I didn't cut down the nettles now 3 weeks ago!