dp alleles have variable effects on wing length and shape and on the thoracic cuticle. Presence of wing phenotype indicated by o = oblique in the allelic designation and of thoracic phenotype by v = vortex or cm = comma. The wing effect is an oblique truncation affecting the margins of the first and second posterior cells in weak alleles and reducing wings to approximately half normal length in extreme genotypes, where the truncation is more nearly perpendicular to the long axis of wing. Margins remain intact; angle between veins L2 and L5 increased, and intercrossvein distance decreased. Phenotype resembles rudimentary. Thoracic phenotype comprises five types of hypodermal irregularities: first vortices, second vortices, commas, pre-episternal pits, and posterior invagination; all five have the form of pits, eruptions, or raised pits of the cuticle (Metcalfe, 1970, Genetics 65: 627-54). First vortices are hypodermal pits or eruptions located posterolaterally on the scutum; they disrupt the acrostichal rows, resulting in surrounding whorls of microchaete. Second vortices are located anterolaterally on the scutum and resemble first vortices morphologically. Commas are comma-shaped depressions at the anterior margin of the scutum. The pre-episternal pit is in the pre-episternal plate immediately anterior to the sternopleural chaetae, which sometimes exhibit disturbed orientation (Metcalf, 1969, DIS 44: 91). The posterior invagination occurs between the laterotergite plate and the metanotum (Metcalf, 1969); different alleles exhibit different combinations of these traits. Musculature attached to disturbed regions of the cuticle often degenerates (Metcalfe, 1970). Some alleles show reduced body size and small weak legs (dph, dpobw females, dpolv/dpov). Phenotypic expression enhanced by increased temperature during development; wing and thorax effects show dominance when heterozygotes exposed to increased temperatures at 12-16 and 8-10 hr of pupal life, respectively (Blanc and Child, 1940, Physiol. Zool. 13: 65-72). Normal larvae fed 6-azauracil produce adults with oblique phenocopies; 6-azauracil feeding suppresses dp (Rizki and Rizki, 1965, Science 150: 222-23), su(r) enhances the oblique phenotype (Stroman, 1974, Hereditas 78: 157-68). The four genotypes studied [dpo2, dpovN, dpv2, and dpv; e(dpv)] show increased orotate phosphoribosyl transferase activity during third larval instar and enhanced incorportion of labeled glucose into chitin (Blass and Hunt, 1980, Mol. Gen. Genet. 178: 437-42). Many alleles are lethal when homozygous; they are identified by l in the allelic designation. Lethal stages vary among alleles, e.g., dpolv is embryonic lethal; dplv1, and dplvI die at the egg-larval boundary; dplm homozygotes die primarily at larval ecdysis between the first and second larval instar with some death at hatching and at ecdysis of second-instar larvae; dpobm homozygotes die mostly at hatching but a few die during first and second larval instars (Metcalfe, 1971, Genet. Res. 17: 173-83). In Me/+ heterozygotes, many dp alleles show a dominant oblique effect when heterozygous for dp+ and dp; dpv is an exception (Carlson, 1959). dpv homozygotes normal; show thoracic phenotype only if third chromosomes homozygous for e(dpv).