By Denw
United Kingdom 
I have heucheras all around the garden which are showing the classic symptoms of vine weevils, semi circular nibbles in the leaves, eventually dying due to their roots being eaten. I have finally found some culprits but they they are not as expected, instead of pale brown maggot like grubs these are small,fat black grubs. Does anyone know what there are? Thanks
22 Sep, 2011
Answers
Thank you for your help. I left the creatures in a box overnight and can see now that they are small slugs as they have stretched out and have tentacles. Strange. Maybe they are opportunists feasting on the dying roots caused by vine weevils in the first place..I was about to buy bio control for vine weevils, hence my confusion at finding something else seemingly causing the damage!
23 Sep, 2011
They could be Letherjack larvae. They are about this time of year, eat roots of grass had Heuchera and are black. They cause damage, so you will need to get rid of them.
22 Sep, 2011