RNA interference (RNAi), one of the strategies that organisms use to defend against invading viruses, is an important tool for functional genomic analysis. In insects, the efficacy of RNAi varies amongst taxa. Lepidopteran insects are, in large part, recalcitrant to RNAi. The overall goal of this study is to overcome such insensitivity in lepidopterans to RNAi. We hypothesize that over‐expression of core RNAi machinery enzymes can improve RNAi efficacy in traditionally recalcitrant species. A transgenic Bombyx mori strain, Baculovirus Immediate‐Early Gene, ie1, promoter driven expression of silkworm Dicer2 coding sequence (IE1‐BmDicer2), which over‐expresses BmDicer2, was generated by piggyBac transposon‐mediated transgenesis. Two indexes, the ratio of animals that showed a silencing phenotype and the duration of silencing, were used to evaluate silencing efficiency. Significant knockdown of target gene expression was observed at 48 h postinjection at both the transcriptional and translational levels. Furthermore, we coexpressed B. mori Argonaute 2 BmAgo2）and BmDicer 2 and found that 22% of the animals (n = 18) showed an obvious silencing effect even at 72 h, suggesting that coexpression of these two RNAi core machinery enzymes further increased the susceptibility of B. mori to injected double‐stranded RNAs. This study offers a new strategy for functional genomics research in RNAi‐refractory insect taxa in general and for lepidopterans in particular.

A passive direct methanol fuel cell (DMFC) with a novel anode structure and operated in neat methanol is reported. The anode incorporates a methanol barrier that is composed of a methanol‐resisting pervaporation film (PVF), a buffer cavity and a water‐resisting PVF. The new anode allows for control of the rate of methanol transportation from the fuel tank to the anodic side of the membrane electrode assembly (MEA) and for retention of water recovered from the cathode to the anode, issuing an efficient anodic reaction and a high proton‐conduction of the Nafion membrane. Such a passive DMFC fed with neat methanol reaches a maximal power density of 29.0 mW cm−2 and an energy efficiency of 23.1%, in comparison with a DMFC with a single methanol‐resisting PVF (energy efficiency = 7.8%). The performance of the passive DMFC system remained constant over 400 h of continuous operation.