I found some of these lovely little grubs in a potted plant that I bought at the nursery. I looked them up in my insect field guide, since I didn’t want to squash them if they were beneficial insects. They’re not. They’re the larvae of the Vine Weevil (from the largerRoot Weevil family) they feed on a plant’s roots and then hatch into those brown/black beetlelike bugs that eat notches out of the leaves on Broadbeans, Rhodedendrons and countless other things. So they got squished. And you should do the same if you see them too.
Root weevils in general can do a lot of damage to leaves. They tend to come out at night so the best way to catch them is to collect them in the evening in a jar. If you dig around the bottom of the plant too you might find some of the grubs above. These are best dealt with in the Autumn.