They are called Strawberry Snails and Slugs - The snails are simply mollusks, related to oysters and clams. They are tiny, but deadly to the strawberry plant and fruit. The slugs are also tiny, and lay their eggs in a slimy shaded mass in your strawberry plant. Your clue that you have either of these problems is that you will see silvery trails winding around the plant or the affected area of the plant. You will not readily see them in the heat of the day.
Here is some advice that we read on a gardening site that seems to work.
Strawberry Seed Beetles (black, about 1cm long) remove seeds from the outside of the fruit and also eat into it- these beetles are also attracted to weed seeds. A slug killer would see them off, but it is not advisable to use chemicals near harvest time. Make sure that nearby weeds are kept down, clear away any dead leaves and garden rubbish, and sink some jam jars into the soil around the bed - a lot of the beetles will fall into them, which will reduce their numbers. It may also be worth finding out if there is an organic slug repellent that would be effective against them, which I intend to do myself.Another tip is to use a vinegar based treatment to deter them. Try using a solution of apple cider vinegar and spray the strawberries several times a day. The mix was 1 tablespoon vinegar to a litre of water.