This cover picture publicizes an article by Wellcome Bender, et al., entitled, "Molecular Genetics of the Bithorax Complex in Drosophila melanogaster". This article details the sequencing a very storied part of the fruit fly genome, known as the Bithorax complex. Mutations in this region of the fly genome can transform a fly's abdomen (a body segment that possesses halteres in flies) into a thorax (a body segment that possesses wings) into a fly that look as if it has two thoracic segments (and thus two sets of wings). Although the science in the paper is new, even groundbreaking for the time, it was known that mutations could transform a two-winged fly int a four-winged fly since the early twentieth century. Geneticists debated for many years whether these types of large discontinuous changes were beneficial for evolution. Although most geneticists don't currently think homeotic mutants are important drivers of evolution; it is indisputable that they have been important for understanding how genes are turned on and off during development. Understanding how flies have lost their wings has been one of the most important tasks of mid-to late-twentieth-century molecular development.