## 3 Results
### Identification of the Main Volatile Components from Orange Juice
When D-Limonene was applied alone, its electrophysiological response achieved the same or a slightly higher intensity than the other components (Figure 2D, _t_-tests \(p\) = 0.4736, \(p\) = 0.2943; Figure 2E, _t_-tests \(p\) = 0.2824, \(p\) = 0.0695; and Figure 2E, _t_-tests \(p\) = 0.9720, \(p\) = 0.0095). In conclusion, D-Limonene plays a key role amongst the orange juice volatiles in attracting _B. dorsalis_. The Attractiveness of D-Limonene to Adult B. dorsalis of Different Ages and Time Periods and Its Impact on Oviposition Behavior  
Olfactory trap assays were conducted to evaluate the attractiveness of D-Limonene to _B. dorsalis_ at different ages during different time periods. The findings revealed that the age of the D-Limonene significantly impacted its attraction to adult flies. At 3 to 9 days of age, D-Limonene exhibited almost no attraction to male and female adult flies, with an attraction rate of approximately 10%. However, at 12 days of age, D-Limonene significantly attracted both male and female flies (Figure 3A,B: a two-way ANOVA where \(p\) = 0.0002, \(p\) = 0.0202). Adults at 12 days of age were employed to test the attractiveness of D-Limonene during two different time periods. The finding suggested that the circadian rhythm had no significant effect on the attraction of D-Limonene, as it was capable of attracting adult _B. dorsalis_ from 9:00 to 17:00 and from 17:00 to 9:00 the following day (Figure 3C: a two-way ANOVA where \(p\) = 0.0868, \(p\) = 0.7066). Given that orange juice is the primary source of egg attraction, the impact of D-Limonene on the egg laying behavior of female flies was evaluated. Compared to the orange juice source, D-Limonene barely induced female flies to lay eggs, with an average number of eggs of 8, compared to 210 with the orange juice source (Figure 3D: a two-way ANOVA where \(p\) < 0.0001). Figure 2: The behavioral and electrophysiological responses produced by the mixtures of chemicals with a high abundance. (**A–C**) The attractiveness of combinations with or without D-Limonene. (**D–F**) The electrophysiological response of _B. dorsalis_ to the mixtures and to D-Limonene by itself (N = 5, ns: not significant, \({}^{+}\)\(p\) < 0.05, \({}^{**}\)\(p\) < 0.01, \({}^{***}\)\(p\) < 0.001, and \({}^{***}\)\(p\) < 0.0001). The Candidate Olfactory Receptors Mediate the Perception and Behavioral Response of B. dorsalis Adults to D-Limonene  
To characterize the olfactory receptor types of _B. dorsalis_ responsible for perceiving D-Limonene, we evaluated the behavioral and electrophysiological responses of olfactory co-receptor mutants to D-Limonene. The results indicated that the odorant receptors (ORs) played a significant role in the attraction of D-Limonene to _B. dorsalis_. Compared to the wild-type adults, the _IR8a-\({}^{-/-}\)_ and _IR25a-\({}^{-/-}\)_ were strongly attracted by D-Limonene (Figure 4A,B: a two-way ANOVA where \(p=0.2096\), \(p=0.5695\) and \(p=0.2925\), \(p=0.9051\)). _Oroo-\({}^{/-}\)_ adults almost completely lost the behavioral response to D-Limonene (Figure 4C: a two-way ANOVA where \(p<0.0001\), \(p<0.0001\)). Using the EAG recordings, the variances in the perception of D-Limonene between the olfactory coreceptor mutants and wild-type adults were contrasted. The results demonstrated that the absence of co-receptor _IR25a-\({}^{/-}\)_ and _IR8a-\({}^{/-}\)_, had no significant effect on the electrophysiological response of adults to D-Limonene, and there was no significant difference in the response of the mutants and wild-type adults to this substance over six doses. At high doses, the _IR8a-\({}^{/-}\)_ and wild-type adults had different responses to D-Limonene (Figure 4D,E: a two-way ANOVA where \(p=0.0421\), \(p<0.0001\) and \(p>0.9808\), \(p>0.5077\)). In the absence of the odor receptor co-receptor _Oroo-\({}^{/-}\)_, _B.