I read somewhere that vine weevil eggs are tiny & almost invisible to the naked eye. They could be slug or snail eggs. Did you squish them?

Yes Beattie and thanks. I have some large lime green insects that I think are called Katydids that appear ealy in July, I wondered if it could be them. You never see a small one, they are just big and scary!

I had to google katydid - it's what I'd call a bush cricket. Katydid is the american name for them. They're really cool - we used to have them patrolling the bathroom ceiling when we lived in an old cottage with wisteria on it. :-)

how about ant pupa[cocoons]. I have them in the compost heap and they fit this description. Last year I had a nest in a large terracotta pot.

I've just seen that they were about 1cm long - not snail / slug eggs then! And too big for ants eggs too.
I suppose they could have been grasshopper or cricket eggs.