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 (<i>B. dorsalis</i>, <i>Z. cucurbitae</i>, <i>Z. tau</i>) and characterized the eggs' volatile profiles by GC-MS. Within 6 h, female attraction rates to egg stimuli varied significantly by species combination. <i>B. dorsalis</i> females were attracted to conspecific eggs at 39.33%, to <i>Z. cucurbitae</i> eggs at 28.67%, and to <i>Z. tau</i> eggs at 0%. <i>Z. cucurbitae</i> females showed attraction rates of 22.67% to <i>B. dorsalis</i> eggs, 13.00% to conspecific eggs, and 1.33% to <i>Z. tau</i> eggs. <i>Z. tau</i> females exhibited 27.67% attraction to <i>B. dorsalis</i> eggs, 13.67% to <i>Z. cucurbitae</i> eggs, and 18.33% to conspecific eggs. Oviposition assays confirmed strong interspecific effects, with <i>B. dorsalis</i> eggs stimulating the greatest egg-laying. GC-MS analysis revealed distinct volatile profiles, with <i>B. dorsalis</i> eggs producing the highest number of unique compounds (57), potentially explaining their strong behavioral effects. In total, 79 volatiles differed significantly between <i>Z. cucurbitae</i> and <i>B. dorsalis</i> eggs, 73 between <i>Z. tau</i> and <i>B. dorsalis</i> eggs, and 91 between <i>Z. cucurbitae</i> and <i>Z. tau</i> eggs. These findings reveal a behavioral hierarchy where <i>B. dorsalis</i> is the most responsive to egg volatiles, <i>Z. cucurbitae</i> is intermediate, and <i>Z. tau</i> 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.