INFLUENCE OF SEX RATIO AND DENSITY OF MOSQUITOES ON THE EFFICACY OF IR3535® AND DEET 203 (200 female:60 males). CPT with 100 females:100 males was signifi cantly longer than that in the other treatments, averaging greater than 5 h, whereas CPT with 200 females:60 males was signifi cantly shorter than that in all other treatments (Figure 2). CX. QUINQUEFASCIATUS CPTs against Cx. qui nquefasciatus (Figure 3) averaged longer in all treatments than that against the other species and were likewise infl uenced by the treatment (p 0.01). Unlike the Aedes and Anopheles trials, Culex CPT was longest in the absence of males (p 0.01). This suggests a possible male facilitation or stimulation of, rather than net interference with, female feeding. IR3535® was comparable to DEET (as presented in the Repellents section): it provided complete protection for approximately 6 h in the absence of males. CPTs dropped signifi cantly to between 4 and 5 h in the other treatments, with the short- est duration at the 3.3:1 sex ratio for Ae. aegypti. AN. AQUASALIS The results for An. aquasali s are given in Figure 4. The infl uence of the density and sex ratio manipulation on CPT was statistically signifi cant (p = 0.01) and resembled that observed in Ae. aegypti but higher than that in Cx. quinquefasciatus. CPT values were also lower on average across the male/female treatment combinations than those for other species. The mean CPT with 100 female:100 male mosquitoes was approximately 120 min, sig- nifi cantly longer than that in other treatments (p 0.02). With 200 females alone, CPT with IR3535® declined to 48 min, as presented earlier. Results were similar for the other treatments, and none differed statistically. Based on these results, we infer that the pres- ence of males did not strongly infl uence the biting frequency of the females (Figure 3). Figure 3 . Repellency of 20% IR3535® against Anopheles aquasalis and determination of time to confi rmed bite. The values are shown as mean CPT ± standard deviation (n = 5).

JOURNAL OF COSMETIC SCIENCE 204 REPELLENCY OF IR3535® AND DEET Considering all subjects, mean CPTs across IR3535 treatments differed signifi cantly among mosquito species (p 0.0001). Mean CPT was greatest against Cx. quinquefasciatus (294 ± 64 min), followed by Ae. aegypti (197 ± 85 min) and An. aquasalis (65 ± 39 min). The ability of IR3535® and DEET to repel mosquitoes was compared usi ng 200 females and no males Cx. quinquefasciatus and An. aquasalis females only (N = 200 Cx. quinquefas- ciatus or An. aquasalis females per cage). The outcome was principally infl uenced by mos- quito species. Against Cx. quinquefasciatus, CPTs of IR3535 and DEET were 378 ± 52 and 360 ± 38 min, respectively. For repellency against An. aquasalis, the mean CPT was considerably less at 48 ± 25 and 72 ± 7 min for IR3535 and DEET, respectively. In neither species was the difference between repellents statistically signifi cant (Figure4) (p 0.05). DISCUSSION The objective of this study was to investigate t he infl uenc e of sex ratio and density of mosquitoes on the effi cacy of IR3535® and DEET in cage tests, and to possibly add breadth to considerations of standard cage testing methodologies beyond female mosqui- toes–only conditions (2). The investigation is relevant in practice because data from cage testing are used in mosquito repellent product development and to complement the fi eld data that are required for federal registration and public health trials (1,3). As a baseline study, we compared the effi cacy of 20% IR3535® and 20% DEET under stan- dard female-only conditions against Culex quinquefasciatus and An. aquasalis. Both products repelled Culex for a signifi cantly longer time than the Anopheles mosquitoes (Figure 5). Figure 4. Re p ellency of 20% IR3535® against Anopheles aquasalis and determination of time to confi rmed bite. The values are shown as mean CPT ± standard deviation (n = 5).