The main accomplishments of the Molecular Entomology Unit are: 1. Utilization of gene editing tools for studying the importance of arthropod salivary gland genes. We generated two knockout (KO) mosquito lines by CRISPR/Cas9 to functionally characterize D7L1 and D7L2, two abundantly expressed salivary proteins from the yellow fever mosquito vector Aedes aegypti. The D7s bind and scavenge biogenic amines and eicosanoids involved in hemostasis at the bite site. D7-KO mosquitoes had longer probing times than parental wildtypes. These results confirmed the role of D7 proteins as leukotriene scavengers in vivo. We also investigated the role of D7 salivary proteins in Plasmodium gallinaceum infection and transmission. We also demonstrated that D7 long-forms are important for pathogen infection since KO mosquitoes had fewer Plasmodium gallinaceum parasites than wild-type (WT) mosquitoes. During blood feeding, salivary proteins are injected into the host skin, and some of them are reingested along with blood. We hypothesize that the reingested D7s play a vital anti-inflammatory role in the midgut microenvironment, which has important consequences for pathogen infection in the mosquito. The information generated by this work highlights the biological functionality of salivary gene products in blood feeding and pathogen infection. 2. Mosquito saliva modulates inflammasome activation and facilitates flavivirus infection in vitro. We show that Aedes aegypti salivary gland extract inhibits the function of crucial immune proteins and thereby interferes with viral sensing and subsequent downstream pathways during DENV and ZIKV infection. Mosquito saliva downregulated NLRP3 expression triggered by dengue (DENV) and Zika (ZIKV) virus infection. We also show that Ae. aegypti SGE downregulates gene expression of key innate immune signaling molecules important for DENV and ZIKV recognition, infection, and subsequent inflammasome activation. Taken together, we found that Ae. aegypti SGE is key in modulating innate immunity during DENV and ZIKV infection. We demonstrate the importance of salivary components of vectors in the pathogenesis of arboviruses and will enable a more in-depth comprehension of the intricate interplay among mosquitoes, viruses, and their human host. This study provides important insights into how mosquito saliva modulates host innate immunity during viral infection and may further help in the development of drugs with pan-viral activities. 3. Structural and functional comparisons of salivary α-glucosidases from the mosquito vectors of medical importance. Although it has been shown that the salivary glands of several mosquito species exhibit α-glucosidase activities, the specific enzymes responsible for sugar digestion remain understudied. We studied the salivary α-glucosidases from the mosquito vectors Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus and compared their functions and structures. We show that all three enzymes were expressed in the salivary glands of their respective vectors and were secreted into the saliva. These proteins exhibited α-glucosidase activity, with preference for sucrose compared to p-nitrophenyl-α-D-glucopyranoside. We also solved the crystal structure of the Ae. aegypti α-glucosidase bound to two calcium ions at a 2.3 Ångstrom resolution. Molecular docking suggested that the Ae. aegypti α-glucosidase preferred di- or polysaccharides compared to monosaccharides, consistent with enzymatic activity assays. Comparing structural models between the three species revealed a high degree of similarity, suggesting similar functional properties. Based on our modeling efforts combined with functional assays, the α-glucosidase orthologs studied herein are highly similar and likely possess similar functional properties. 4. Saglin, a mosquito salivary protein from Anopheles gambiae is essential for Plasmodium parasite infection of the mosquito midgut. CRISPR/Cas9 was used to evaluate the role of how the Anopheles gambiae salivary protein Saglin, a putative salivary gland receptor for Plasmodium falaciparum, mediated malaria parasite infection and transmission. By engineering a loss-of-function mutant in mosquitoes, we showed that the absence of Saglin impaired development in mosquito midgut of the rodent malaria parasite P. berghei and the human malaria parasite P. falciparum, lowering the parasite burden of subsequent stages and preventing efficient transmission at low infection densities. We also showed that Saglin facilitates Plasmodium colonization of the mosquito midgut, but does not contribute to salivary gland invasion. Furthermore, we were able to show that Saglin deletion has no signifficant fitness cost in laboratory conditions, suggesting this gene would be an interesting target for gene drive approaches to block malaria transmission.