Homeosis

Homeosis is the transformation of one body part into another, arising from mutation in or misexpression of specific developmentally critical genes. It may be caused by mutations in Hox genes, found in animals, or others such as the MADS-box family in plants. Homeosis is a characteristic that has helped insects become as successful and diverse as they are.

Reference
Lodish et al, 2003. Molecular Cell Biology, 5th Edition. . W.H. Freeman and Company, New York.