A precondition for colour vision is the presence of at least two spectral types of photoreceptors in the eye. In the Apocrita, trichromacy is the basal pattern. Most species possess three different photoreceptor types in their compound eyes, with peak sensitivities in the ultraviolet, blue and green range of the light spectrum, and the corresponding visual pigments, the opsins. Experimental studies in basal Hymenoptera report from one to four photoreceptors, but results remained inconclusive. To better understand the evolution of photoreceptor diversity in the Hymenoptera, we studied the global pine pest Sirex noctilio (Siricidae), which belongs to the superfamily Siricoidea, the closest sister group of Apocrita. Our aim was to i) characterise the visual opsins of S. noctilio by genomic comparisons and phylogenetic analyses of the opsin genes and ii) to identify the photoreceptor types of the compound eye by electroretinography. We identified three opsins in the genome, homologous to the hymenopteran LW1, LW2 and UV opsin genes. Electroretinographical measurements confirmed the presence of two photoreceptor types maximally sensitive to 527 and 363 nm in the compound eye. The lack of a SW-homologous opsin gene and a corresponding receptor suggests that S. noctilio is a UV-green dichromate.