N. lapillus may be aware of the risk of capture by byssus threads as small mussels without close neighbours are usually preferred to dense beds. Often mussels are forced open, but when boring is employed it is usually on the dorsal area near the posterior (Hughes and Dunkin, 1984) . This is away from the mussel’s foot (extended in picture) which attaches the byssus threads, but also near the mussel’s nutritious digestive gland and where the shell is thinner.