Performance of the Ifakara OBS as a contamination station. Panel A): Average number of female mosquitoes caught per night in the Ifakara OBS fitted with either polyester net or black cotton cloth treated with pirimiphos methyl. There were significantly less mosquitoes caught in the OBS with treated polyester net than with either the treated black cotton cloth or the control. Panel B): Percentage of all mosquitoes caught in the OBS that died within 24 hours. Significantly more mosquitoes died where the contaminant was used than in the controls. The Y-error bars represent 95% confidence intervals.