Using the electroretinogram (ERG) technique the spectral efficiency of the compound eye of the glasshouse whitefly Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae) and its main parasitoid Encarsia formosa (Gahan) (Hymenoptera: Aphelinidae) was measured at selected wavelengths between 340 nm and 670 nm. The form of the ERG for both T. vaporariorum and E. formosa was found to be monophasic in nature. For both male and female T. vaporariorum and female E. formosa a primary peak of efficiency occurred in the blue-green-yellow region, peak 520 nm and a secondary peak in the ultraviolet (UV) region. The compound eye of female E. formosa gave a significantly greater response in the UV region than either the dorsal or ventral regions of the compound eye of T. vaporariorum relative to the responses in the blue-green-yellow region. T. vaporariorum has divided compound eyes with distinct dorsal and ventral regions. In this study it was found that the percentage response in the UV, of the dorsal region of the eye, is significantly greater than that of the ventral region of the eye relative to the percentage response in the blue-green-yellow region and there is a significant shift in the blue-green yellow peak towards the right of the spectrum.

Using electroretinogram recordings, the response of Lutzomyia longipalpis sandfly eyes to a range of wavelengths of light was measured, and spectral sensitivity determined. The eyes of both male and female adult sandflies were found to respond maximally to light in the ultraviolet region (at 340 nm) with a secondary peak in the blue-green-yellow region at 520 nm for females and 546 nm for males. The Mann-Whitney U test showed no significant differences between males and females at corresponding wavelengths.

The responses of male and female Lutzomyia longipalpis (Lutz & Neiva) to different wavelengths of light was tested by presenting the sandflies with two light sources simultaneously, a series of test wavelengths between 350-670 nm and a 400 nm control. To test whether L. longipalpis could discriminate between the test and control, three sets of experiments were carried out in which the test wavelengths were presented at higher, equivalent or lower intensity than the control. In all three experiments, ultra-violet (350 nm) and blue-green-yellow (490-546 nm) light was more attractive to L. longipalpis than the control wavelength. However, at low intensity, UV was less attractive, than equivalent or higher intensity UV light. At intensities equivalent to or higher than the control wavelength, ultra-violet light was more attractive than blue-green. Furthermore, at low intensity, green-yellow (546 nm) light was more attractive to males whereas blue-green (490 nm) was more attractive to females. Blue-violet (400 nm) and orange-red (600-670 nm) light were least attractive in all three sets of experiments. Response function experiments indicated that the responses were dependent on both intensity and wavelength and that therefore more than one photoreceptor must be involved in the response. The results indicated that L. longipalpis can discriminate between different wavelengths at different intensities and thus have true colour vision. It also suggests that L. longipalpis may be able to navigate at dusk or under moonlight or starlight conditions using light in the blue-green-yellow part of the spectrum. The difference in response of males and females to light in this region is interesting and may indicate the different ecology of the sexes at night. Overall, these results may have important implications for sandfly trap design.

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