ON THE VISUAL-PERCEPTION OF THE EYES IN ADULT HYALOMMA-TRUNCATUM TICKS (ACARI, IXODIDAE)

Adult Hyalomma truncatum ticks with uncovered and foil-covered eyes we re exposed to an upright-positioned rectangle as a target giving a lum inance contrast ratio of 5:1 at a sun-simulating radiation. The transm ission rate of the foil was less than 0.003%. Significantly (p less th an or equal to 0.05) more locomotorally active ticks with uncovered ey es (36.6%) responded to the target than ticks with foil-covered eyes ( 7.3%). When the rectangle was illuminated by monochromatic light at wa velengths ranging between 420 and 648 nm, the target induced a positiv e scototaxis in ticks with uncovered eyes regardless of the wavelength range. Ln contrast, ticks with covered eyes did not exhibit a positiv e scototaxis at wavelength ranges of 553-585 and 608-648 nm and very f ew ticks responded only to other wavelength ranges. The results indica te that the eyes are the only or at least the most essential sense org ans in the visual system of adult H. truncatum ticks.