The yellow fever mosquito (Aedes aegypti) is a mosquito that can spread dengue fever, chikungunya, and yellow fever viruses, and other diseases.They are active and bite only during the daytime.Mosquitoes are vectors(agents) which spread various diseases.
e.g. Yellow fever is caused by a flavivirus; it is transmitted by the bite of Aedes mosquitoes, which had become infected by biting an infected human or animal (a monkey). An infected mosquito is a source of infection for the rest of its life.