Electrophysiological response of Dendroctonus pseudotsugae and Ips paraconfusus (Coleoptera: Scolytidae) to selected wavelength regions of the visible spectrum

Abstract

Electroretinograms (ERGs) were recorded from the compound eyes of both sexes of Dendroctonus pseudotsugae Hopkins and Ips paraconfusus (Lanier). Light stimuli between 400 and 650 nm were delivered to the compound eyes through a monochromator connected to a fiber-optics and lens light-delivery system. Stimulus intensity was regulated with neutral density filters. The averaged spectral response curves were similar for both species and sexes. The spectral sensitivity curves disclosed two sensitivity maxima, one in the blue region (450 nm) and one in the green region (510 to 530 nm). These correspond well with behavioural data on scolytids and with response peaks reported in other insects and provide evidence that the scolytid visual system consists of two receptor types. The blue receptors are probably used in navigation during the initial stages of the dispersal flight and the green receptors for the detection of spatial information during host selection.