Do the parasitic Psithyrus resemble their host bumblebees in colour pattern?

It has been claimed for the parasitic Psithyrus bumblebees that each parasite species resembles closely its particular narrow range of bumblebee host species in colour pattern. The generality of colour-pattern resemblance is assessed by applying quantitative tests at three levels of resolution in the detail of the colour patterns. The results show that at all three levels the parasites and hosts are significantly more likely to share similar colour patterns than would be expected by chance in Europe, but not in North America. Parasites do not appear to be significantly more specialised in host choice in Europe than in North America, although there is more evidence of parasite-host co-speciation in Europe than in North America. Parasite-host resemblance appears most likely to be explained by Mullerian mimicry. For the host-specific Psithyrus, the host species might serve as the most influential model because necessarily the host species must co-occur with the parasite and must be common.