The prevalence of in-door caught Anopheles gambiae and An. funestus and monthly rainfall pattern in Masaika village, 1998-2001 (a) and Kirare, 2004-2009 (b), Tanga region, Tanzania. The prevalence is shown as mean number of An. gambiae or An. funestus caught per CDC light trap per month. Note that this parameter has different scale on the y-axis in the two sub-figures. The monthly rainfall has been recorded at the Maji Depot Tanga Rainfall station (Ministry of Water and Irrigation, Tanzania) and is shown as a gray area plot.