Volatile Compounds from Eggs of Three Fruit Fly Drive Aggregation and Oviposition

Insects use oviposition secretions containing deterrent signals to regulate intra- and interspecific competition and structure resource partitioning; certain Tephritidae display a striking reversal of this strategy. Herein, we induced female aggregation and oviposition using eggs from the three fruit fly species (B. dorsalis, Z. cucurbitae, Z. tau) and characterized the eggs' volatile profiles by GC-MS. Within 6 h, female attraction rates to egg stimuli varied significantly by species combination. B. dorsalis females were attracted to conspecific eggs at 39.33%, to Z. cucurbitae eggs at 28.67%, and to Z. tau eggs at 0%. Z. cucurbitae females showed attraction rates of 22.67% to B. dorsalis eggs, 13.00% to conspecific eggs, and 1.33% to Z. tau eggs. Z. tau females exhibited 27.67% attraction to B. dorsalis eggs, 13.67% to Z. cucurbitae eggs, and 18.33% to conspecific eggs. Oviposition assays confirmed strong interspecific effects, with B. dorsalis eggs stimulating the greatest egg-laying. GC-MS analysis revealed distinct volatile profiles, with B. dorsalis eggs producing the highest number of unique compounds (57), potentially explaining their strong behavioral effects. In total, 79 volatiles differed significantly between Z. cucurbitae and B. dorsalis eggs, 73 between Z. tau and B. dorsalis eggs, and 91 between Z. cucurbitae and Z. tau eggs. These findings reveal a behavioral hierarchy where B. dorsalis is the most responsive to egg volatiles, Z. cucurbitae is intermediate, and Z. tau is the least responsive, a ranking that correlates with significant differences in the eggs' volatile compositions. This study directly links a behavioral status in interspecific oviposition to species-specific egg volatile profiles.