Transmission of Dirofilaria ursi Yamaguti, 1941 (Nematoda: Onchocercidae) of black bears (Ursus americanus) by blackflies (Simuliidae)

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Abstract
Microfilariae of Dirofilaria ursi Yamaguti, 1941 from black bears (Ursus americanus) developed to the third stage in Simulium venustum Say and perhaps other simuliids but not in culicids, tabanids, and ceratopogonids. Malpighian tubules were the only site which supported development to the third stage. In blackflies held at 27 and 23 °C, D. ursi reached the third stage in 5 and 9 days respectively. At 18 °C larvae did not reach the third stage in blackflies held for 16 days.The effects of temperature (18, 23, and 27 °C) on growth of D. ursi in the vector are described. Morphological changes in larvae during development to the infective stage at 23 °C are reported. The prepatent period of D. ursi in black bears is 210–271 days.