The mosquitoes were transferred to a Ziploc® plastic bag containing a sheet of absorbent tissue paper and each mosquito was crushed on the tissue to determine the number of mosquitoes that engorged in the test and upon which dye-colored treatment they fed upon. Between tests, the used organdy cloth and collagen membranes were removed from the reservoir and discarded. At this time, positions of the colored CPDA-1/ATP solutions in the reservoir wells were refreshed. Although preliminary testing (see below) showed neither a color nor a side-of-tunnel preference by the mosquitoes, these factors were routinely alternated from one test to another. Nitrile gloves were always worn when handling wind tunnel equipment to avoid contamination with human skin-derived compounds. Before starting a day of bioassay tests, all equipment in the wind tunnel was routinely wiped with ethanol-moistened paper towels to ensure cleanliness of check details the bioassay equipment. We provide some data from our initial testing of the wind tunnel, in part to demonstrate normal host-seeking and feeding behaviors of mosquitoes in the apparatus. In initial testing, feeding wells contained expired human blood in half the feeding stations and 10−3 M ATP in CPDA-1 in the other half. Human breath was introduced for one minute near the feeding station. Data on the distribution of the mosquitoes in the tunnel, the number of probes, and the number of engorging mosquitoes were taken. Twenty trial runs were made over several days and at various times of day. Summing over the 20 trial runs, the mosquitoes distributed themselves at the end of each 10-min test as follows: 87% left the canister; of those, 17% were closer to the canister end of the tunnel, the remainder nearer to the end containing the feeding reservoir; and 56% of those that left the canister were on top of the feeding station. Of those that left the canister, 46% tested engorged. We recorded 418 probes into the feeding wells (total number of mosquitoes = 20 × 20 = 400; total number of mosquitoes that left the canister = 349). We conducted some simple statistical testing to determine if there were differences in feeding or probing on the two food sources, also if there was a day or time-of-day effect, using the lme4 package (Bates et al. 2011) in R (R Development Core Team 2012). Details are given below in the Experiment 1 section. We found that mosquitoes preferentially engorged from human blood (105 vs 54, p < 0.01) but did not preferentially probe in wells with human blood (p = 0.89). The variance estimates for both the day effect and the time-of-day effect were essentially zero. To achieve our first objective, four experiments were conducted to evaluate the role of carbon dioxide, water vapor, ATP, and thermal stimuli, and to demonstrate the importance of each stimulus in the elicitation of feeding behavior by Ae. aegypti and Ae. albopictus.