4.1. Microinjection

Microinjection was first used to introduce dsRNA for RNAi [5], and soon after this technique was successfully applied to insects: D. melanogaster [9] and then to the moth, H. cecropia [11]. However, during subsequent years, RNAi through injection of dsRNA in moths has been demonstrated to have great variability in success and is not as straightforward as shown in other insect taxa [12,75]. Nevertheless, quite a number of studies have successfully performed RNAi in a number of different moth species by using injection (Table 1). Similar to other insect taxa, RNAi based on dsRNA injection has been applied to all life stages in moths: (1) egg stage [15,43]; (2) larval stage [23,24,33]; (3) pupal stage [17,27]; and (4) adult stage [25,31] (Table 1).

Microinjection has proved to be a direct and effective means in dsRNA introduction for RNAi. An important shortcoming to the use of microinjection in insects is mechanical damage during injection, which is most often pronounced when targeting embryos and neonatal larvae and pupae [76]. The mechanical damage may also have side effects or even cover the effect when studying the function of genes related to behavior and survival using RNAi. In addition, dsRNA injection is not suitable for RNAi-based pest control.