UNCONVENTIONAL ULTRAVIOLET SENSITIVITY SPECTRA OF ASCALAPHUS (INSECTA, NEUROPTERA)

The spectral sensitivity of 21 eye preparations of Ascalaphus (Libellu loides) macaronius (Insecta, Neuroptera) has been re-measured using an up-to-date spectral scan method. 1. Dorso-frontal and ventro-lateral eyes have different spectral characteristics with peaks of sensitivity at 329 +/- 8 nm (n = 15) and 343 +/- 4 nm (n = 5) (P = 0.002), respec tively. 2. The absorbance of the visual pigment layer, K, determined f rom the shape of the spectral sensitivity curves is 1.3 +/- 1.8(n = 15 ) for dorso-frontal eyes and - 1.0 +/- 0.3(n = 5) for ventrolateral ey es, thus implying higher selfscreening in the dorso-frontal eyes and n arrowing of the spectral sensitivity curves as regards to a template v isual pigment in ventro-lateral eyes. 3. Plotting K versus spectral se nsitivity peak wavelength lambda(max) revealed an inverse correlation between these variables with K = 42.5 - 0.126 lambda(max) at r = 0.88( n = 19). 4. Extracts of ommochromes and carotenoids (Figs. 4 to 6) do not allow to account for the above diversity of optical properties of the Ascalaphus eye (Fig. 7).