Fleas are most attracted to the colors red, blue, and black. Yellow and white targets attract the fewest fleas. Cat fleas are also drawn to sources of light. They respond best to green-yellow light. However, color plays a minor role in host-finding, as fleas use a combination of many attraction stimuli.
One study observed fleas’ response to different colored targets: White, yellow, black, blue, and red. The red and blue targets were most attractive, with 79% of fleas responding Fig 1. Black and yellow were moderately attractive. The worst performing color was white, attracting only 36.9% of fleas.
Fig 1 Percent of fleas responding (y-axis) to different colored targets (x-axis).
Target & Background Color
A similar experiment used white and black targets, and against white and black backgrounds. Fleas were significantly more attracted to the black targets, regardless of background color. The best response (68.9%) occurred with a black target on a white background. The worst response (23.4%) occurred with a white target on a white background.
Surface Area of Color
Within the same study, a white target was bisected with a red band. The band was tested with varying thicknesses: 3, 6, and 9 cm. The solid white target attracted the fewest fleas, and the solid red target was most attractive. The fleas’ response progressively increased as the red surface area grew.
Cat fleas are positively phototactic, meaning they’re attracted to sources of light. The green to yellow part of the spectrum attracts the most fleas, specifically at wavelengths between 500 and 530 nm Fig 2. Green-yellow light attracts over twice as many fleas as standard white light. Adding a green filter to lighted flea traps makes them significantly more effective.
Fig 2 Percent of fleas responding (y-axis) to light at different wavelengths in nanometers (x-axis) compared against 345 nm light.
Light passing through a light green or yellow-green filter also outperforms standard light (1.67 and 1.15 times, respectively). Other colors fail to attract more fleas than white light. Red, magenta, and pink filters perform most poorly. Cat fleas can’t see wavelengths beyond 630 nm (red light).