Fig. 2. Homeotic transformations in adult male. Male abdomens were cut along the dorsal midline and flattened on a slide. The dorsal surface of each abdominal segment has a rectangular plate of hard cuticle called the tergite. Only half of the tergites of the 4th, 5th and 6th abdominal segments (numbered) are visible, as well as the genitalia at the bottom. (A) In wild type, the 5th and 6th tergites are pigmented. The ventral surface of abdominal segments is composed of soft cuticle called the pleura. On the ventral midline of the pleura, there are small plates of harder cuticle called sternites. In wild type, the 6th sternite (shown by arrows) can easily be distinguished from the more anterior sternites by its different shape and by the absence of bristles. In wild-type males, the 7th abdominal segment present in embryos and larvae does not contribute to any adult structures after metamorphosis. (B) iab-7²⁸⁰males harbor a complete transformation of A7 into A6, as revealed by the presence of a large 7th tergite and sternites (arrows). (C) In iab-7^R73 males, however, there is only a weak transformation of A7 into A6, as revealed by the small 7th tergite and the absence of a 7th sternite on the ventral side. (D) In iab-6,7^IH, A6 is completely transformed into a copy of A5. However, A7 is only partially transformed into a segment of intermediate identity between A5 and A6, as seen by the shape of the 7th sternite, which resembles the 6th, but harbors a few bristles (A5 character). This indicates that in iab-6,7^IH, iab-7 is not completely inactivated (E)In iab-5,6^J82, both A5 and A6 are transformed into a copy of A4. (F) In iab-5,6^J81 the residual pigmentation on the 6th tergite, as well as the shape of the 6th sternite show that A6 is not fully transformed into A4, but instead, into a mixture of identity between A4 and A6, suggesting that the iab-6 domain is not completely inactivated by the deletion. (G) In iab-4,5,6^DB, A5 is transformed into A3. However, as in iab-5,6^J81, the 6th segment harbors features of A6, suggesting that iab-6 is also not completely inactivated by the deletion.