abdomen, 3, 269 genital segments, 270–271 musculature, 272–273 number of segments, 270 structure of segments, 270–272 abdominal appendages, 273–280 cerci, 276–277 evolution of, 273 gills, 277–278 larval locomotion and attachment structures, 141–142 modified prolegs, 280 primitive hexapods, 274–275 scoli, 280 secondary sexual structures, 278–279 secretory structures, 278 sensory structures, 276–...