Innate Preferences for Radial Gradient Pattern Cues in the Cotton Bollworm, <i>Helicoverpa armigera</i>

Information is lacking regarding the visual cuesused by Helicoverpa armigera mothsduring nectar feeding. Here, we investigated the preference for radial gradientpatterns in H. armigera moths. Theresults indicated that both sexes shared a preference to plain flower models ofblue and cyan. The radial gradient pattern (cyan as nectar guide color and blueas petal color) was more attractive than its component plain colors (cyan orblue), especially in male moths. Number of corolla petals did not influence theattractiveness of the cyan-blue pattern. The addition of a tertiary floralattractant to white-blue or cyan-blue radial gradient patterns coulddramatically enhance the attractiveness of visual cues in males rather thanfemales, suggesting that males gave a higher weight in olfactory modality thanfemales gave, while females gave a higher weight in vision modality than malesgave. All together, we found an optimal combination of floral cues in H. armigera sexes as follows: A tertiaryfloral attractant (2 μL dose of phenylacetaldehyde, benzyl acetate, andsalicylaldehyde mixed in 26:15:2) added to white-blue radial gradient flowermodel (3 cm in diameter). To our knowledge, this is the first time that rosecurve and radial gradient tools were used to simulate floral pattern in thestudies of flower-visiting insects.