|Adult butterflies are often attracted to damp or moist ground and may congregate at such areas in large numbers. In most cases, these groupings, or "puddle clubs," are made up entirely of males. They drink from the moisture to gain water and salts (sodium ions) that happen to come into solution. This behavior helps males replenish the sodium ions lost when they pass a packet of sperm and accessory gland secretions to the female during copulation. The transferred nutrients have been shown to play a significant role in egg production and, thus, female reproductive output.