Illustration of the modified arena.

<p>(<b>A</b>) A Dudley tube painted black from inside was flanked by 2 cotton rolls secured in place by syringe needles that delivered CO₂. Samples of defibrinated sheep blood mixed with solvent only or spiked with DEET were loaded on these cotton rolls, which were subsequently covered with Parafilm. (<b>B</b>) An aerial view of the arena. Mosquitoes were placed on a mosquito cage accessible from the top and having a camera (not shown) attached to the left. The Dudley tube was connected to a water bath (not shown) and the syringe needles to a CO₂ tank (not shown).