The traditional view of interactions between arboviruses and their arthropod vectors is that vector hosts become increasingly resistant to parasites; parasite attenuation occurs; or through the process of coevolution, resistance and attenuation occur in concert. Detrimental effects from arboviruses are only seen when vector and virus are not yet well adapted. Results from this study indicate that eastern equine encephalomyelitis (EEE) virus reduces survival and reproduction (fitness) of the mosquito Culiseta melanura, which is required for transmission of EEE virus in North America. Mosquito virulence was not measurably attenuated in virus isolates recovered 55 year apart. This virus did not affect the ability of mosquitoes to obtain a blood meal or the rate of mosquito oocyte development. Results from this study support those from earlier investigations with other mosquito-virus interactions and suggest that reproductively successful arboviruses can have detrimental effects on their mosquito vectors.