The Delta is a novel by Colin Wilson published in 1987.
The Delta is a novel in which Niall heads for the Delta to investigate the source of a vital spiritual force which causes insects to grow large.[1]
Dave Langford reviewed The Delta for White Dwarf #100, and stated that "The Delta is better than promised by The Tower, but the crudeness of its SF tropes detracts from the more interesting Wilson philosophy."[1]