In order to identify candidate RER whorl forming proteins in Ae aegypti midgut epithelial cells, we took advantage of the fact that an amino acid meal is sufficient to induce whorl unwinding, which simplifies both EM analysis and protein identification by mass spectrometry because it eliminates interference from abundant blood meal proteins. Moreover, since we found that RER whorl unwinding occurs rapidly once feeding begins (Figure 1 ), we were able to use a short recovery time of only 30 min to enrich for microsomal proteins that are present in the mosquito midgut prior to feeding. The LC-MS/MS analysis identified 127 proteins using microsomal midgut protein samples from unfed and amino acid fed mosquitoes. Eight proteins were considered candidate whorl associated proteins based on their known location and function in ER and Golgi membrane compartments (see Table 1 ). Since three of the candidate proteins encoded COPI coatomer subunits, and the peptide frequency was lower for each of the proteins in samples from fed mosquitoes compared to unfed mosquitoes, we chose alpha-COPI as a representative coatomer subunit and performed RNAi knockdown experiments. Data presented in Figures 6, 7 , and 8 show that loss of alpha-COPI expression is associated with the absence of RER whorls in unfed mosquitoes, as well as membrane disorganization and ER swelling in midgut epithelial cells of amino acid fed mosquitoes. These data suggest that alpha-COPI, and likely two or more of the other seven COPI coatomer subunits, are involved in RER whorl formation and maintenance in midgut epithelial cells of unfed female mosquitoes. Based on the association of RER whorls with untranslated AeET mRNA transcripts in unfed mosquitoes, we predicted that RER whorls inhibited the translation of AaET transcripts. However the data in Figure 9A clearly show that this is not the case since sugar fed alpha-COPI dsRNA injected mosquitoes lacked both RER whorls and AaET protein expression. Surprisingly, while synthesis and secretion of AeET was not altered in blood fed alpha-COPI deficient mosquitoes, expression of three abundant late phase proteases (AaSPVI, AaSPVII, AaLT) was inhibited ( Figure 9B ), indicating that COPI vesicle transport is required for later events in the blood digestion process.