Homozygous cad¹ embryos from cad¹/+ mothers develop into nearly normal first-instar larvae, which, however, lack cuticular structures of the external terminalia, e.g., the anal tuft, parts of the anal pads and the terminal sense organs. Distribution of cad⁺ gene product in such embryos indistinguishable from that in their cad¹/+ and +/+ sibs, evidently maternally derived. cad¹/+ offspring from cad¹/cad¹ oogenic cysts indistinguishable from those from cad¹/+ cysts; larvae lack portions of the eighth abdominal segment and sometimes parts of the fourth and less frequently other even-numbered abdominal segments; frequently they develop into normal adults. cad¹/cad¹ embryos from homozygous cad¹ cysts display variably abnormal segmentation; head and anterior thorax normal; many posterior segments deleted with T2 and odd-numbered abdominal segments more resistant to deletion; most of eighth abdominal segment and terminalia (but not some parts of posterior spiracles) deleted; replaced by small plates of sclerotized cuticle resembling mouth hooks.