Master of Science in Life Sciences / This thesis explores the feeding structures of insects, which have evolved over millennia to utilize a variety of dietary sources. It examines the mouthparts of insects feeding on plants, other bugs, or vertebrate blood, analyzing how these structures influence or limit their diet. Focusing particularly on mosquitoes, which are a significant public health threat due to their role as vectors of deadly diseases, we investigate the unique sexual dimorphism and diet, females' blood-feeding behaviors and the differences in the dual-pump feeding mechanisms of Aedes aegypti and Culex quinquefasciatus. Specifically, we investigated the effect of fluid viscosity on the sugar-feeding behavior and the pumping dynamics of males and females via force-feeding assays and electromyography (EMG) recording. Results showed varied pumping contraction frequencies among mosquito species and sexes that align with host feeding preferences. Furthermore, the study confirms that both species and sexes significantly influence sucrose intake, with Aedes aegypti females notably consuming more at higher concentrations, a trend not mirrored in Culex quinquefasciatus females. By studying the effects of fluid viscosity on feeding behavior and pumping dynamics, we inform computational models of the ingestion pumps that will help us gain insight into how the evolution of blood feeding.