Imaginal Discs

In Pl. 39, fig. 2, and Pl. 40, fig. 7, a sketch is given of the main imaginal discs. Those inside the head capsule cannot be seen well in whole mounts but appear in sections In fig. 2, the six imaginal discs corresponding to the adult legs have been formed at L 1–L 3. By focusing the preparation, higher up are seen the discs belonging, in segment two, to the wings (W), and in segment three, presumably to the halteres. At this stage the two are nearly the same size. In Pl. 40, fig. 7, the discs relating to the hind abdominal region are shown at (HA). This region is photographed in a previous paper (Gatenby, 1959, Pl 26, fig. 12). The testes are found in the sixth abdominal segment (TS, in fig. 7). In Pl. 40, fig. 10, the male genital ducts are forming at (MG), and the intestine, still intact, has apparently shed its intima (INT), though the writer is not quite sure of the identity of this material.