Butterfly wings display pattern elements of many types and colors. To
identify the molecular processes underlying the generation of these pa
tterns, several butterfly cognates of Drosophila appendage patterning
genes have been cloned and their expression patterns have been analyze
d. Butterfly wing patterns are organized by two spatial coordinate sys
tems. One system specifies positional information with respect to the
entire wing field and is conserved between fruit flies and butterflies
. A second system, superimposed on the general system and involving se
veral of the same genes, operates within each wing subdivision to elab
orate discrete pattern elements. Eyespots, which form from discrete de
velopmental organizers, are marked by Distal-less gene expression. The
se circular pattern elements appear to be generated by a process simil
ar to, and perhaps evolved from, proximodistal pattern formation in in
sect appendages.