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Mud-puddling, or simply puddling, is a behaviour most conspicuous in butterflies, but occurs in other animals as well, mainly insects; they seek out certain moist substances such as rotting plant matter, mud and carrion and they suck up the fluid. Where the conditions are suitable, conspicuous insects such as butterflies commonly form aggregations on wet soil, dung or carrion. From the fluids they obtain nutrients such as salts and amino acids that play various roles in their physiology, ethology and ecology. This behaviour also has been seen in some other insects, notably the leafhoppers, e.g. the potato leafhopper, Empoasca fabae.
Lepidoptera (butterflies and moths) are diverse in their strategies to gather liquid nutrients. Typically, mud-puddling behavior takes place on wet soil. But even sweat on human skin may be attractive to butterflies such as species of Halpe. More unusual sources include blood and tears. Again, similar behaviour is not limited to the Lepidoptera, and for example, the various species of bees commonly called sweat bees are attracted to various kinds of sweat and tears, including that of humans, and other bee species have been recorded as doing so to various degrees.
In many species puddling behaviour is restricted to males, and the presence of an assembly of butterflies on the ground acts on Battus philenor for example, as a stimulus to join the presumptive mud-puddling flock.
On soil
In tropical India this phenomenon is mostly seen in the post-monsoon season. The groups generally include several species, particularly members of the families Papilionidae and Pieridae.
Males seem to benefit from the sodium uptake through mud-puddling behaviour with an increase in reproductive success. The collected sodium and amino acids are often transferred to the female with the spermatophore during mating as a nuptial gift. This nutrition also enhances the survival rate of the eggs.
When puddling, many butterflies and moths pump fluid through the digestive tract and release fluid from their anus. In some, such as the male notodontid Gluphisia crenata, this is released in forced anal jets at 3 second intervals. Fluid of up to 600 times the body mass may pass through and males have a much longer ileum (anterior hindgut) than non-puddling females.