Chemical, Color, and Tactile Cues Influencing Oviposition Behavior of the Hessian Fly (Diptera: Cecidomyiidae)

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Abstract
The effects of several plant characters on the oviposition behavior of Hessian flies were investigated by presenting mated females with various combinations of chemical, color, and tactile cues in choice bioassays. When applied to filter paper, one plant equivalent (PE) of a chloroform extract of wheat leaves stimulated 438 times more egglaying than chloroform controls. One PE of oats extract stimulated 10 times more egglaying than chloroform controls. Wheat extracts stimulated 12 times more egglaying than oats extracts. Doseresponse tests using wheat extracts showed that females were stimulated to oviposit at concentrations as low as 0.01 PE; they laid more eggs as dosage increased. Higher dosages of oats extract (1.0 PE) were required to elicit significantly more oviposition than occurred on chloroform controls. In separate tests with and without wheat extract, females laid more eggs on yellow, green, and orange papers than on blue and red papers. Choice tests using green and grey filter paper strips indicated that egglaying responses were stimulated primarily by hue rather than intensity of colors. Tactile cues associated with venation of grass leaves were mimicked by making parallel grooves (“veins”) down the long axis of wax-covered filter paper. In tests without wheat extract, females laid 28 times more eggs on the veined surface than on the smooth surface. With wheat extract present, the veined surface elicited only two times more egglaying than the smooth surface. Vertical grooves received four times more eggs than horizontal grooves. In a test using a factorial treatment design with chemical, color, and tactile cues either absent or present, females laid the most eggs on the treatment that combined all three cues. Removal of chemical cues caused a significantly larger reduction in egglaying (93%) than did the removal of either tactile or color cues (70%)