Color-pattern modifications of butterfly wings induced by transfusion and oxyanions.

The color-pattern determination of butterfly wings was studied, focusing on the cold-shock-induced color-pattern modifications of a species of butterfly, Vanessa (Cynthia) cardui (Lepidoptera: Nymphalidae). It was shown that the modification property could be transferred to the noncold-shocked individuals by the transfusion of hemolymph taken from the cold-shocked individuals, suggesting the existence of an unknown diffusible factor or hormone, induced or activated by the cold shock. The involvement of a receptor tyrosine kinase for the color-pattern modifications was tested by the simple application of some oxyanions such as sodium tungstate, sodium molybdate, and molybdic acid to pupae, since these oxyanions have been known to up-regulate the process of phosphorylation via receptor tyrosine kinases in general. It was shown that they could modify the wing color-pattern in a way very similar to the cold shock. Moreover, the topical applications of sodium tungstate or molybdic acid induced large ectopic black spots on the treated pupal wings. Among the treatment methods, the sodium tungstate treatment was by far more effective than the cold shock treatment itself. Taken together, these data suggest that an unknown cold-shock hormone activates the process of phosphorylation via a receptor tyrosine kinase necessary for the color-pattern development.