sets of mechanosensory organs located at the base of the lepidopteran antenna, Böhm's bristles and the Johnston organ. These fields of receptors respond to different directions of antennal movements. Antennae are also capable of sensing odor, humidity, and temperature. Sane et al. (2007) was able to demonstrate that it was the mechanosensors that were responsible for flight stability as opposed to the other sensory organs, because when the flagella were removed and then reattached, all antennal nerves were severed excluding those at the base (Böhm's bristles and the Johnston organ). Genetics In segmented organisms there are genes called Hox genes, which determines the development of serial homologs, or repeating structures within an organism (e.g. jointed appendages of arthropods or vertebrae in mammals). In insects, the thorax is separated into different segments. One of the things that the Hox gene Ultrabithorax (Ubx) is responsible for, is specifying the identity of the third thoracic segment of their body. Proper hindwing development in a number of insect species is dependent on Ubx, including butterflies, beetles, and flies. In fruit flies, (Ubx) is responsible for the formation of the halteres during metamorphosis. If this gene is experimentally deactivated, the haltere will develop into a fully formed wing. This single homeotic gene change results in a radically different phenotype, but also begins to give us some insight into how the ancestors of flies' hindwings may have originally evolved into halteres. Though it is clear that Ubx is the primary gene responsible for hindwing formation, Ubx also regulates other genes once expressed. Weatherbee (1998) postulated that differences in Ubx expression patterns or levels may not be responsible for the observed physiological changes. Instead, he suggested that Ubx-regulated target gene sets were the direct source of the observed changes. Several Ubx-regulated target genes have been identified, including two direct targets, spalt and knot, which are expressed in the wing and repressed in halteres. Other genes which are expressed in wings and repressed in halteres have also been identified, but whether or not they act as direct targets of Ubx regulation are still unknown. Dynamics Dipteran insects along with the majority of other insect orders use what are known as indirect flight muscles to accomplish flight. Indirect insect flight muscles are composed of two sets of perpendicular muscles (see left figure) that are attached to the thorax (instead of directly to the wing base as is the case