• apyrene spermatozoon;
  • eupyrene sperm bundle;
  • saline concentration;
  • spermatophore size


Although sodium ions induce puddling behavior in males of some butterfly species, the role of sodium ions in male life history is unclear. Newly emerged laboratory-reared males of the swallowtail butterfly Papilio xuthus were allocated to five adult diets: water (as a control) and 0.001, 0.01, 0.1 or 1 mol/L saline solution. Males preferred to take 0.1 mol/L saline solution. We attempted to hand-pair males after two days of intake. Males on all diets, except those taking 1 mol/L saline solution, were likely to couple. Males taking 0.01 mol/L saline solution produced the largest spermatophore, although there were no significant differences in the number of eupyrene sperm bundles and apyrene spermatozoa between saline-taking males and control males. Salt accumulation in the male body also had little effect on the number of both types of spermatozoon in the spermatophore.