Why is habitat modification used in black fly management?

• A. To increase water flow to breeding sites.
• B. To attract natural predators to streams.
• C. To disrupt breeding sites by altering streams and surrounding vegetation.
• D. To accelerate larval development.

Answer: (C)

Habitat modification works by making the stream environment less suitable for black fly breeding. Black fly larvae attach to substrates in fast-flowing, well-oxygenated water, so altering the streams and surrounding vegetation changes the physical conditions they need to reproduce and develop. By modifying flow patterns, substrate availability, and surrounding vegetation, you disrupt the breeding sites and reduce larval survival and emergence.

The other ideas don’t fit this approach: increasing water flow to breeding sites would often improve conditions for larvae rather than disrupt them; attracting natural predators is a biological control tactic, not a habitat modification focus; and accelerating larval development would worsen the problem rather than address habitat suitability.