In this talk I will give an overview of my PhD project. The main objective of this project is to study how the nutritional condition in mosquitoes affects their immune system and therefore their resistance or tolerance to survive infections. I will use a combination of experimental and ecological approaches to study the effects of different diet in the survival of mosquitoes. I will focus on two pathogens, West Nile Virus and Plasmodium. In addition, I will study both the impact that nutritional condition of mosquitoes could have on the transmission and prevalence of these pathogens. I will analyze how different environmental factors affect the nutritional condition of mosquitoes studying different locations, and seasons and using long-term datasets.