Utsuri is the first commercial phenotype derived from dark-pigmented larvae. We
found Utsuri offspring only in progeny of Utsuri parents, suggesting a genetic control of
this pattern. In these crosses, a variable proportion of the progeny had a dark pigmentation
already at hatching, from which a smaller and variable proportion of offspring developed
the Utsuri pattern (up to 16%). The variable proportion implies on a complex genetic
control with possible environmental effects. In a practical aspect, crosses of Utsuri
parents, though yielding a relatively low proportion of Utsuri offspring, also yield
light-pigmented sibs that in part develop a Kohaku phenotype which is of commercial
value.