sheathed microfilaria of Wuchereria bancrofti.   This larva exists in the bloodstream of humans with the adults housed in lymph nodes.  Mosquitoes of 77 different species can transmit this parasite by inadvertently sucking the microfilaria up with a blood meal. The microfilaria further develop in the mosquito and in the infective filariform stage are introduced into the bloodstream of a new host with the bite of the mosquito.  400x