Figure 4.

 Cuticular phenotypes of ss mutants. The antennal and leg phenotypes of ss mutants have been described by others [see Lindsley and Zimm (1992) and references therein]. (A,B) Antennae from wild-type (A) and ss^a (ss^D114.10/ss^D114.4) (B) adults. The first (A1), second (A2), and third (A3) antennal segments and the arista (Ar) are indicated. The antennal tarsus in ss^a mutants is judged to have T2 identity by the following criteria: Paired rows of stout bracted macrochaetae present ventrally (Hollingsworth 1964) are like those on the second leg; the most distal bristle pair in each segment is larger than more proximal pairs; on average, there are three pairs of bristles in the fifth tarsal segment (Lawrence et al. 1979); and there are no posterior transverse bristle rows in the second tarsal segment. (C) Antenna from a ss null mutant (ss^D115.7). A3 has no bristles or trichomes, and most of the distal tarsal region is absent. (D–E) Distal second leg of wild-type and a ss null mutant. Tarsal segments 2–4 and part of segment 1 are deleted in E. (F,G) Wild-type and ss null mutant maxillary palps. The mutant palps are truncated. (H– K) Wild-type (H,I) and ss null mutant (J,K) first instar antennal and maxillary sense organs (AnSO and MxSO). The AnSO is indicated with a large arrow, the MxSO with a large arrowhead, and the dorsomedial papilla (DMP) with a small arrowhead. In the mutant the AnSO is cauliflower-shaped and has no clear stalk, and migration of the DMP is impaired. Scale bars, A–G (shown in A), 100 μm; H–K (shown in H), 10 μm.