## 3 Results
Right), and females, with 67.4% \(\pm\) 2.0% of attraction (Figure 1, Center), but again, volatiles from 3-7-day-old dung were unattractive to both horn fly sexes. In the oviposition tests, egg number per female was significantly (\(p\leq\) 0.05) higher in samples with cattle dung than in blanks, either in fresh dung or in aged dung (Figure 2). Comparing among treatments, the egg-laying was the highest in a sample with fresh cattle dung, with 2.54 \(\pm\) 0.27 eggs per female, and it was significantly different from samples with 3-, 5-, and 7-day-old dung, where oviposition was 1.39 \(\pm\) 0.19, 1.07 \(\pm\) 0.18, and 1.09 \(\pm\) 0.45 eggs per female, respectively. Egg-laying among samples with aged cattle dung was not significantly different. Considering the flies were separated from the feces with pieces of tulle, the egg-laying was influenced by volatile cues emanated from cattle feces. Behavioral responses of horn flies to single compounds present in volatile blends emanated from cattle dung were also evaluated in this study (Figures 3 and 4). In the olfactory tests, the \"Y\"-tube olfactometer allowed us to measure the attraction provoked by most of the single compounds tested. \(p\)-Cresol, \(\alpha\)-pinene, \(\beta\)-pinene, \(D\)-limonene, and \(\beta\)-caryophyllene at 0.05 \(\upmu\)g per mL in hexane exhibited significant attraction in the olfactometer, compared with the blanks, where 70.0% \(\pm\) 5.0% (\(p\leq\) 0.001), 63.3% \(\pm\) 2.9% (\(p\leq\) 0.001), 73.3% \(\pm\) 7.6% (\(p\leq\) 0.001), 60.6% \(\pm\) 9.5% (\(p\leq\) 0.05), and 73.3% \(\pm\) 2.9% (\(p\leq\) 0.001) of the mixed-sex flies chose the treatment, respectively (Figure 3, Left). Testing with male flies, \(\alpha\)-pinene, \(\beta\)-pinene, \(D\)-limonene, and \(\beta\)-caryophyllene were attractants, with 71.9% \(\pm\) 10.3% (\(p\leq\) 0.01), 77.8% \(\pm\) 19.2% (\(p\leq\) 0.05), 82.1% \(\pm\) 6.2% (\(p\leq\) 0.001), and 77.8% \(\pm\) 19.2% (\(p\leq\) 0.05) of male flies selecting the treatments, respectively. However, \(p\)-cresol did not cause a significant difference in the olfactory response of males compared with the blank, where 55.6% \(\pm\) 19.2% of the flies chose the treatment (Figure 3, Right). Using female flies, \(p\)-cresol, \(\alpha\)-pinene, \(\beta\)-pinene, and \(\beta\)-caryophyllene were attractive to females, where 76.2% \(\pm\) 4.1% (\(p\leq\) 0.001), 56.4% \(\pm\) 3.1% (\(p\leq\) 0.01), 73.5% \(\pm\) 8.7% (\(p\leq\) 0.01), and 71.4% \(\pm\) 7.1% (\(p\leq\) 0.01) of the flies chose the treatment. Differently, \(D\)-limonene was not attractive, where only 49.8% \(\pm\) 6.0% of the female flies chose the treatment (Figure 3, Center). Therefore, \(p\)-cresol was unattractive to male horn flies, and \(D\)-limonene was not attractive to female horn flies. Figure 2: Oviposition of female horn flies exposed to volatiles from fresh and aged cattle dung. Columns are mean number of eggs laid per female horn fly \(\pm\) SE. Different letters on the columns indicate significant differences among treatments, including blanks, based on the Likelihood Ratio (LR) test (\(p\leq\) 0.05); N = 6. In the oviposition bioassays, comparing among the single compounds, the egg-laying was the greatest in samples with \(p\)-cresol and \(\alpha\)-pinene, with 0.84 \(\pm\) 0.18 and 0.80 \(\pm\) 0.21 eggs per female, respectively, and it was significant different (\(p\leq\) 0.05) from its blanks, where the egg numbers per female were 0.21 \(\pm\) 0.04 and 0.03 \(\pm\) 0.01, respectively. Figure 4: Oviposition of female horn flies exposed to single compounds present in volatile blend emanated from cattle dung. Columns are mean number of eggs laid per female horn fly \(\pm\) SE. Different letters on the columns indicate significant differences among treatments, including blanks, based on the Likelihood Ratio (LR) test (\(p\leq\) 0.05); N = 6. Figure 3: Olfactory responses of horn flies to single compounds present in volatile blend emanated from cattle dung.