2.7. Bioassays of Drosophila Flies

Transgenic female flies at 2–5 days post-eclosion were subjected to the contact/feeding bioassay. A 5-fold serial dilution was prepared with 5000 mg(a.i.)/L omethoate stock to a concentration range from 10,000 mg(a.i.)/L to 0 mg(a.i.)/L. A total of 100 µL of each dilution was added to the surface of a settled 3 mL agar (2% w/v) containing sucrose (1.2% w/v) and acetic acid (0.4% v/v) in a Drosophila vial (25 mm × 95 mm). Transgenic flies were transferred to the vials. The mortality was scored after 24 h. Dead flies, as well as those displaying no coordinated movement (difficulty to walk up the vial and to lift their feet), were cumulatively scored as “dead.” At least three replicates of 20 flies per replicate were used for each concentration. LC₅₀ values were calculated using PoloPlus 2.00 software. Other insecticide bioassays were performed in a similar way as described above. The insecticides used include omethoate, imidacloprid, cypermethrin, deltamethrin and tau-fluvalinate.