Fig. 6. Effects of JH levels on Fas2^spin and genitalia rotation. (A) Phenotype of adult or pharate adult male genitalia after topical application of pyriproxyfen (a JH analog) at the white pupae stage. The use of a half-lethal dose of pyriproxyfen (LD₅₀) induces mis-rotation phenotypes in both the hatched and non-hatched populations (16% and 68%, respectively). In the non-hatched flies, the partial and no rotation phenotypes were four and six times higher than in the hatched population, respectively. At the lethal dose of pyriproxyfen (97% lethality; LD₉₇) the pharate adult males showed a higher proportion of partial (44%) and non rotated (44%) genitalia with only 12% showing a wild-type phenotype. (B) Genetic interaction between Fas2^spin and the Methoprene-tolerant (Met) [Rst(1)JH] gene. The loss of Met function (Met^K17) completely suppresses the Fas2^spin rotation defects, while two extra copies of the Met gene aggravated the extent of genitalia rotation in Fas2^spinR5 flies. In Fas2^spinR5 males, the rotation of the genitalia stopped most frequently (51%) between 180° and 270°, and the non rotated phenotype was not observed. The Fas2^spinR5/Y; Met⁺ (3x) males died as pharate adults and the extent of rotation was dramatically reduced. In most cases (64%), rotation stopped between 0° and 90°, whereas 26% of the males showed non rotated genitalia.