Developmental origin of even spacing between the microchaetes of Drosophila melanogaster

In D. melanogaster, evenness of spacing is a prominent feature of the patterns of microchaetes. As a general explanation of this characteristic, Wigglesworth has suggested a scheme whereby some epidermal cells become singled out (determined) at random to differentiate bristles, and the same potential in neighbouring cells issuppressed by the determined ones. Though this model may be satisfactory for other epidermal regions, the spacing between bristles within some of the mid-dorsal thoracic acrostichal rows is too even to be accommodated.