A beautiful Cepora butterfly rests on a stone along a riverbank where other pierids gather to gain nutrients from alluvial soils.
As our lingering El Niño keeps local bugs in suspended animation, Bug of the Week makes a stop in Costa Rica before returning to Borneo where we recently visited scary potter wasps, stridulating longhorn beetles, fierce arboreal and terrestrial ants, stingless bees, giant millipedes, and pretty lanternflies. This week we meet beautiful Marpesia butterflies on a Pacific beach and pretty Cepora butterflies along a riverbank in Gunung Mulu National Park. These gorgeous butterflies engaged in a poorly understood behavior called “pumping.” No, this is not the kind of pumping Arnold Schwarzenegger or Hans and Franz of SNL made famous with heavy weights and muscular contortions. In previous episodes we met temperate swallowtail butterflies feeding on unusual substrates including carcasses of fish and piles of dung to obtain vital minerals and nutrients not found in nectar of more traditional hosts like the blossoms of flowers.
Marpesia are famous for their glorious colors and wing patterns.
Butterflies frequently “puddle” in muddy soil using their proboscis to gather dissolved elements from moist mineral laden earth. “Pumping” is different. This infrequently observed behavior occurs when a butterfly rapidly imbibes water with its soda-straw-like mouthparts and rapidly expels it from the rear end. In 1963 Walfried Reinthal made the following observations of a swallowtail butterfly pumping at the edge of a swimming pool: “This pumping in of the water through the proboscis and at the same time eliminating it from intestines went on uninterruptedly for about the next twenty minutes. During this interim over two hundred and fifty drops of water were counted …” At a loss to fully explain this behavior Reinthal suggested that perhaps “the insect had to give itself a sort of internal lavage...” Other observations of pumping include those of Eduardo Welling who witnessed a swarm of about 30 swallowtail butterflies pumping in a “stinking hollow of mud” near a lagoon in Quintana Roo. He wondered if the behavior was related to the excessive heat and humidity of the tropical day.
Watch as a lovely Marpesia sips water from the sand and expels droplets from its abdomen about once every five seconds. An equally lovely Cepora drinks along a rainforest riverbank and shoots water out its derrière. This poorly understood behavior in butterflies is called pumping.
Butterflies have many mechanisms to warm and cool themselves, the business of thermoregulation. Basking in the sun, avoiding conductive heat loss in the wind, and shivering are all used by butterflies to warm themselves. Respiratory cooling by evaporation and shade seeking are mechanisms used by butterflies to chill out on a hot day. In his treatise on thermoregulation in butterflies, Harry Clench suggested that pumping might be a way for a butterfly to rapidly warm or cool itself depending on the differential between ambient air temperature and the temperature of the water being pumped from the soil. Although I find the notion of butterflies performing self-lavage odd and intriguing, hey, in the world of insects stranger things have happened. Watching beautiful Marpesia and Cepora expelling droplets of water is a strange and intriguing site to behold irrespective of the reason.
Acknowledgements
Bug of the Week gives special thanks to Carlos and Lawrence and our friends Pat, Kristie, Bob, Dan, and Paula who inspired this episode. “Behavioral thermoregulation in butterflies” by Harry Clench, “About the “pumping action” of Papilio at water” by Walfried Reinthal, and “More observations of the “pumping” action of moths at water, with notes on observations in Quintana Roo” by Eduardo Welling were consulted in preparation of this episode.