Abstract
Simulium penobscotensis Snoddy and Bauer preferentially colonized vegetation of the genera Potamogeton and Sparganum at water velocities ≥ 0.30 m/sec. The Potamogeton and Sparganum vegetation was primarily in water < 1.25 m in depth, and in beds with 50–100% vegetation cover. There was an 80% increase in potential habitat of this description when Penobscot River water levels increased by 40 cm.