Do black fly larvae prefer still or moving water?

• A. Still
• B. Both
• C. Neither
• D. Moving

Answer: (D)

Black fly larvae thrive in moving water, where oxygen levels are high and the current continuously brings in food particles. They anchor to submerged rocks in fast-flowing parts of streams and rivers, using specialized hooks to stay in place while the water washes over their feeding structures. The moving water not only provides ample oxygen but also delivers a steady supply of organic matter they filter-feed on, while helping prevent the surface from becoming clogged with sediment. In still water, oxygen can be lower or fluctuate and sediments can settle, making feeding and respiration more difficult. So the preferred habitat is moving water, which is why that option is the best fit.