Files in this Data Supplement:

• Supplemental Figure S1 -

  Fig. S1. Alignment Polyommatus icarus LW and UV opsins cloned in this study.

• Supplemental Figure S2 -

  Fig. S2. Phylogenetic tree of P. icarus UV opsin genes based upon a neighbor-joining analysis using the Tamura−Nei model model with a correction for heterogenous patterns of nucleotide substitution among lineages. Only the first and second codon positions were used in the reconstruction and the reliability of the tree was tested using 1000 bootstrap replicates. Bootstrap support values >50% are shown. Genbank accession numbers are as follows: Bicyclus anynana (UV, AF484248); Danaus plexippus (UV, AY605546); Heliconius erato (UVRh AY918904); Manduca sexta (Manop2, L78081); Lycaena rubidus (UVRh, AY587904); Papilio xuthus (Px Rh5, AB028218); Papilio glaucus (Pgl Rh5, AF077191); Pieris rapae (PrUV, AB208673); Vanessa cardui (UVRh, AY414074). GenBank accession number of the newly cloned Polyommatus icarus UVRh is EU088115.

• Supplemental Figure S3 -

  Fig. S3. Longitudinal section through an ommatidium in the eye of P. icarus that shows red perirhabdomal filter pigment (in addition to the dark screening pigment). Note that not the entire range of pigmentation is seen in this section. Due to the very thin area of pigmentation it almost impossible to contain the pigment over its entire extension.

• Movie 1 -

  Movie 1. Footage showing a P. icarus butterfly given the choice between a 560 nm (+) rewarded feeder and a 450 nm unrewarded feeder. The individual has previously been trained to fly to 560 nm light.