When are adult black flies most active and where do they rest after feeding?

• A. Dawn and dusk; they rest on vegetation near streams after feeding.
• B. Midday; they rest in burrows.
• C. Night only; they rest on the ground near rivers.
• D. Dawn only; they rest on the water surfaces.

Answer: (A)

Adult black flies exhibit crepuscular activity, meaning their flight and host-seeking are strongest at dawn and at dusk when light is lower and temperatures are cooler. This timing helps them move and feed more efficiently while reducing dehydration and predation risk. After feeding, they tend to rest on vegetation near streams because these areas provide shade, concealment, and immediate proximity to their aquatic breeding sites. Being on vegetation near streams also makes it easy for them to take off again and search for more hosts while staying near where they emerged.

So the best choice reflects activity at dawn and dusk and resting on vegetation near streams after feeding. Midday activity is less likely due to heat, resting in burrows isn’t typical for these flies, night-only activity isn’t accurate for their pattern, and resting on water surfaces isn’t common.