2. Materials and methods
2.1. Insect stocks
All of the Drosophila lines were maintained at 25 °C in a standard corn meal/molasses medium [20] with a 12 h/12 h light/dark cycle at 60% humidity. The following fly strains were used: w1118; J36 (yw, M{eGFP,Vas-int.Dm}ZH-2A;;M{RFP.attp}ZH-86Fb); Sco/Cyo; TM3/TM6b; and tub-Gal4 [21]. The mosquito strain (C. pipiens) Shengui is an OP-resistant strain maintained at 26 ± 1 °C with a long-day photoperiod (14 h/10 h light/dark cycle) [22] and [23]. The cotton aphid strain (A. gossypii) was collected in Tai'an, Shandong, in 2010 and reared in the lab at 25 ± 1 °C with a long-day photoperiod (14 h/10 h light/dark cycle).