▁wild ▁type ▁f lies . ▁ ▁D ros oph ila ▁mel an og aster ▁has ▁a ▁series ▁of ▁m ating ▁behav iors ▁that ▁enable ▁them ▁to ▁cop ulate ▁within ▁a ▁given ▁environment ▁and ▁therefore ▁contribute ▁to ▁their ▁fit ness . ▁After ▁Morgan ’ s ▁discovery ▁of ▁the ▁white - ey e ▁mut ation ▁being ▁sex - link ed , ▁a ▁study ▁lead ▁by ▁St ur te v ant ▁( 1 9 1 5 ) ▁concluded ▁that ▁white - ey ed ▁males ▁were ▁less ▁successful ▁than ▁wild - type ▁males ▁in ▁terms ▁of ▁m ating ▁with ▁females . ▁It ▁was ▁found ▁that ▁the ▁greater ▁the ▁density ▁in ▁eye ▁p ig ment ation , ▁the ▁greater ▁the ▁success ▁in ▁m ating ▁for ▁the ▁males ▁of ▁D ros oph ila ▁mel an og aster . ▁▁▁ ▁y : ▁yellow - ▁The ▁yellow ▁gene ▁is ▁a ▁gen etic ▁mut ation ▁known ▁as ▁D mel \ y ▁within ▁the ▁widely ▁used ▁data ▁base ▁called ▁fly base . ▁This ▁mut ation ▁can ▁be ▁easily ▁identified ▁by ▁the ▁at yp ical ▁yellow ▁p ig ment ▁observed ▁in ▁the ▁cut icle ▁of ▁the ▁adult ▁f lies ▁and ▁the ▁mouth ▁pieces ▁of ▁the ▁lar va . ▁The ▁y ▁mut ation ▁compr ises ▁the ▁following ▁phen ot yp ic ▁classes : ▁the ▁mut ants ▁that ▁show ▁a ▁complete ▁loss ▁of ▁p ig ment ation ▁from ▁the ▁cut icle ▁( y - type ) ▁and ▁other ▁mut ants ▁that ▁show ▁a ▁m osa ic ▁p ig ment ▁pattern ▁with ▁some ▁regions ▁of ▁the ▁cut