Keep the soil moist but not saturated. If the worms come to the top it is too wet and they are in danger of drowning. On a long trip, worms can be transported in a box of moist earth or in sphagnum moss obtained from a florists's greenhouse. The earth is better too dry than too wet. Do not use sand.
Worms eat their way through soil.
Sand scratches their insides and kills them. A dead worm is no good for bait. Grasshoppers and crickets can be carried best in a milk bottle plugged with a wad of paper. Crayfish and small frogs should be carried in a can with a few wet leaves but no water. Grubs, obtained from a manure pile, rotting log or old stump, can be carried like angleworms.