Melanism (dark-coloured wings) in a species of moth is controlled by a gene with two alleles. The dominant allele codes for the melanic form and the recessive allele codes for the non-melanic form (pale, speckled wings). Birds are a predator of this species. The melanic form is better camouflaged in areas polluted by carbon deposits from smoke. The non-melanic form is better camouflaged in areas unpolluted by smoke. The frequencies of these two forms of moth were investigated in two populations living in different areas, X and Y, by using moth traps and counting the numbers of each type of moth. The investigation was carried out over a period of time corresponding to twenty-four generations of this species. During this time period, human activity increased in both areas X and Y as towns and roads were developed. During generation 1, a large factory started releasing lots of smoke in area X. Fig. 2.1 shows the results of the investigation. [Figure 2.1]