Resource specialization in puddling Lepidoptera

Lepidoptera feed at mud puddles, dung, and carrion in a behavior known as puddling. Sodium and sometimes protein are feeding cues, are actively collected, and play a potentially important role in lepidopteran nutritional and mating ecology. We showed that montane butterfly species have feeding preferences among mud, herbivore dung, and carnivore dung, and that these preferences differed among butterfly species. The puddling substrates varied in soluble sodium content, with mud having the lowest concentrations and carnivore dung having the highest. Within one species, Pieris napi L., visit frequencies to mud versus dung matched visit frequencies to sand trays filled with sodium solutions matching the concentrations seen in mud or dung. This suggests that the preference hierarchy of this species is driven by soluble sodium concentration. Overall, the results indicate that lepidopteran species specialize on different puddling substrates, likely obtaining different arrays of nutrients. This suggests that there are species- or family-specific roles for puddling nutrients in the overall nutrient budget of the insects.