Flea larvae develop best at ______% relative humidity.

• A. <50%
• B. 50-75%
• C. >75%
• D. 90-100%

Answer: (C)

Flea larvae need moist conditions to survive and molt. In environments where the relative humidity is high, water loss from eggs and larvae is minimized, allowing them to remain active, feed on organic debris, and progress through their developmental stages more efficiently. When humidity is elevated—about 75% or higher—the larvae are less likely to desiccate, which supports faster and more successful development. In drier conditions, they lose water quickly, making survival and development much harder. So the condition that best promotes flea larval development is a relative humidity above 75%.