Color vision is highly conserved in insects including beetles (Coleoptera), facilitated by the differential expression of opsin genes. We searched for UV-, B- and LW-opsins and investigated their expression in three new darkling species: Tribolium confusum, Tenebrio molitor, Zophobas atratus. Single UV- and LW-opsin paralogs were cloned from each species. Any attempts of cloning an ortholog of the B-opsin subfamily failed. Phylogenetic tree reconstruction showed all the new cloned LW-opsins grouped together with LW-opsins from other insects. The same result was obtained for the newly cloned UV-opsins. dS calculations suggests that the darkling beetles diverged very early, more than 25 million years ago. Further analysis identified some residues under positive selection, which might be important for the spectral tuning of opsin genes. Expression analysis revealed that LW-opsin is expressed in all eight photoreceptor cells in T.confusum and T.molitor. UV-opsin is co-expressed with LW-opsin in the R7 cells of these species. In Z.atratus, LW-opsin is expressed in R1 through R6 cells, and also R8 cells, while UV-opsin is expressed in the R7 cell only. The conservation of UV-opsin expression in R7 and LW-opsin expression in R8 is consistent with the lack of B-opsin in the three species. It is therefore concluded that the loss of B-opsin occurred at an early stage of darkling beetle evolution, and that dichromatic vision is an ancestral trait of darkling beetles, which are in general characterized by life histories that are little color stimulus dependent.