Ammonia as a puddling site-marshaling substance for Japanese Papilio butterflies

Abstract

Butterflies, especially the males, often come to dumping grounds to sip water. This behavior is called “puddling”. The aim of the present study was to identify the key substances marshaling eight species of Japanese Papilio butterfly to their puddling sites. We conducted behavioral field experiments and found that ammonia is one of these marshaling compounds. We examined the olfactory sensilla on the antennae of four Papilio species by scanning electron microscopy, transmission electron microscopy, and the single-cell response recording method. We found sensilla responding to ammonia on the ventral surfaces of the antennae of male and female Papilio xuthus and male P. maackii, P. protenor, and P. memnon. We also identified sensilla responding to humidity on the dorsal surfaces of the antennae of male and female P. xuthus. As members of this genus are primarily herbivores, they do not normally approach natural sources of this compound, namely, decomposing urine and dead animal carcasses. However, there was evidence to indicate that water sources emitting ammonia attractant were also often sources of vital Na+ cation that is frequently deficient in the diets of herbivorous butterflies.