The tree-hole mosquitoes Aedes hendersoni and Ae. triseriatus were compared as intermediate hosts of Dirofilaria immitis (dog heartworm). Both species of mosquitoes supported the development of D. immitis to the infective (L3) stage. On post infection day 16 Ae. hendersoni had greater mortality than Ae. triseriatus, and the mean number of infective D. immitis larvae in the heads and mouthparts of Ae. hendersoni was greater than in Ae. triseriatus. The behavior of Ae. triseriatus in nature makes it highly suspect as a vector of D. immitis, but little is known about the natural behavior of Ae. hendersoni as it relates to its potential for transmitting this parasite.