Fig. 4: Gravid population trends from across the United States provide insight into the biotic and abiotic factors that influence Cx. pipiens diapause.

a End-of-season Cx. pipiens gravid trap data (weeks 30–40) provided by locations across the United States. States included in our analysis are denoted in light gray, with individual county-level data included in the statewide analysis shown in dark gray. Iowa is denoted by the red star. For each state, red lines represent the loess-smoothed mean of the gravid (reproductive) population abundance, while gray lines display data from an individual year included in our analysis. The approximate period of diapause receptivity (as defined by our semi-filed experiments) is displayed by the red gradient. b Sites at higher latitudes demonstrated more pronounced declines in gravid trap averages from weeks 30–33 to week 40. c Map of the reported distributions of Cx. pipiens (yellow), Cx. quinquefasciatus (green), and areas of potential genetic hybridization between these species (olive). Site locations providing gravid trap data are shown by the gray dots, while Iowa is denoted by the red star.