Recombination in dihybrid crosses
You have screened for several new recessive mutations in a species of wasp.

Wasps homozygous for apricot (aa) have pale orange eyes. (Wild-type eyes are brown.)
Wasps homozygous for blunt (bb) have short wings. (Wild-type wings are long.)
You make a pure-breeding double-mutant (apricot, blunt) line and cross it with wild-type wasps. The F1 is wild-type in appearance.

You testcross the F1 dihybrids with the double-mutant line