Relative response to colored substrates by ovipositing blackflies (Diptera: Simuliidae). I. Oviposition by Simulium (Simulium) verecundum Stone and Jamnback.

Abstract

Gravid females of Simulium verecundum made up 84% of eight simuliid species trapped on test strips floating on a stream in Algonquin Park, Ontario. When six colored strips with almost equal reflectances were exposed over a midbrown stream background, these females oviposited more on green and yellow than on purple, blue, orange, and red strips. Females oviposited also more on a white than on a black and two grey strips. After the stream background was changed to black, differences were less pronounced, and the preference shifted toward purple and blue among colored strips, and toward light grey among neutral strips, although green, yellow, and white strips still remained the most attractive. With a white stream background few eggs were laid on the strips. Gravid females trapped on sticky strips discriminated little among black and grey strips, but selected preferentially white, and retained a preference for green and yellow. Attractance of the colored strips varied inversely with the reflectance ratio of 450–500 nm/500–550 nm. Attractance of the neutral strips varied directly with their luminous reflectance. Thus both the hue and intensity of light reflected from the strips influenced ovipositing simuliids, but reflectance of the stream-bed background modified the primary effect.