At 47 NEON sites in 2014–2024, a warm 14-day anomaly increased mosquito trap catch below about 18 °C and decreased it above, lower than lab transmission optima of 24–25 °C

Question: lab thermal performance curves predict that mosquito density is unimodal in temperature, with transmission optima of 23.9–25.2 °C for the North American Culex vectors of West Nile virus. If field populations follow such a curve, a warm anomaly must increase catch where the usual temperature is below the optimum and decrease catch where it is above. Approach: we used 43,110 night CO2-trap samples at 513 trap locations on 47 NEON sites (2014–2024, RELEASE-2026 via neonDivData) and Daymet daily air temperature at each trap. A Poisson model with fixed effects for trap location, site-year and site by calendar week gave the effect of the 14-day temperature anomaly before collection as a linear function of the 1995–2024 climatological temperature. Result: the anomaly effect decreased by 0.023 log units per °C of climatology (SE 0.0075). It was positive at cool climatologies and negative at hot climatologies, and it crossed zero at 17.7 °C (site bootstrap 95% interval 16.4–20.5 °C). Only 0.5% of bootstrap draws were in the 22.7–29.1 °C range of lab transmission optima. The crossing stayed at 16.7–20.6 °C for 7-day, 28-day and lagged windows, without Puerto Rico and Hawaii, with equal site weights, and when any one site was left out. A placebo with the anomaly after collection gave no interaction. Lab density curves that we fitted to published Culex trait data peak at 19.5–23.2 °C, so the field crossing is lower than or at the low end of these. Limitations: with count weights, the decrease was present only in the rising half of the season, which a lab curve does not predict, but with equal site weights the difference between halves was not significant. A seasonal-shift (phenology) term explained part of the pattern. Catch shows activity as well as abundance, Daymet is air temperature, and Culex pipiens and quinquefasciatus were rare. The data support a sign change near 18 °C, not a cause.

mosquito · thermal performance curve · NEON · temperature anomaly · thermal optimum · Culicidae · CO2 trap · Daymet · West Nile virus vectors · phenology · Poisson fixed effects · field test of lab predictions