Leviticus 11:20-23

These verses deal with insects. Perhaps the fact that certain insects swarmed rather than flew in a more direct and "natural" way made them unclean. Locusts that hopped may have been clean since this is the normal form of locomotion for birds, which they resembled. The varieties of locusts that crawled were unclean, perhaps because that appeared to be abnormal movement for this insect. [Note: Douglas, p. 56.]