Which trap is best for collecting Culex pipiens?

• A. Light Traps
• B. CO2-baited traps
• C. Gravid Traps
• D. Oviposition traps

Answer: (C)

Gravid females are the most productive target for sampling Culex pipiens because they have already taken a blood meal and are actively looking for a place to lay eggs. A gravid trap uses an infusion and other cues that mimic a suitable standing-water site, drawing these ready-to-oviposit females in, where they are collected. This approach provides a reliable and size-efficient way to monitor the adult female population of Culex pipiens, which is what surveillance aims to track for disease risk.

Light traps pull in many species and a mix of ages, so they’re less specific to Culex pipiens and often yield lower interpretable data for this species. CO2-baited traps attract host-seeking mosquitoes, including Culex, but they target females looking for a blood meal rather than those ready to lay eggs, which can dilute species- and stage-specific information. Oviposition traps lure females to lay eggs and primarily collect eggs or larvae rather than adult females, so they don’t provide a direct read on the current adult population. Gravid traps, by focusing on the egg-laying stage of Culex pipiens, give the most representative snapshot of the adult vector population for monitoring and control decisions.