Hopefully this pic will help. The little knowledge that I know which may be wrong is that they suck the sap out of the plants. We have tried the washing-up liquid tonight and they seemed to dis-like it so fingers crossed. BTW the pic is from the internet.
'there was a young man named jobby,
who haboured an illicit hobby,
with renknowned growing fame,
he put our plants to shame,
that bright young man named jobby'