Mosquitoes are not passive vessels for Plasmodium malaria parasites. Plasmodium parasites participate in complex biological interactions with mosquitoes and pass through several developmental life stages before a mosquito is rendered infective and capable of spreading the parasites to a new host. These elaborate interactions are likely the reason why only mosquitoes in the genus Anopheles are capable of spreading human malaria parasites, and further, why only approximately 60 of the more than 400 known species of Anopheles mosquitoes are competent disease vectors. By comparing mosquito genomes, we can identify patterns of selection, chromosomal inversions, and gene gains or losses that may contribute to vectorial capacity. By studying the transcriptional profile of parasites developing into mosquito-transmissable gametocytes, we can identify parasite factors conducive to disease transmission. Through analysis of polymorphism in parasite genomes, we can learn about local disease transmission patterns and rates.