[Hematophagic rhythm of Simulium quadrivittatum Loew, 1862 (Diptera: Simuliidae)]

A relation between the hematophagic activity of Simulium quadrivittatum and the variation of solar position north of "La Canada" hill (21 degrees 43'N and 82 degrees 54'W), in the central area of the Isle of Youth, was found. Two paraboles were derived. They respond to the equations y = 11.61 + 0.137 S + (-4.727) S2 and y = 17.06 + 0.415 S + (-9.495) S2, for the morning and afternoon values respectively. A higher hematophagic activity, on average, was found in the afternoon (U = 24, P less than 0.05).