A National Weather Service Doppler radar image depicts large numbers of mayflies emerging at dusk from the Upper Mississippi River south of La Crosse, Wisconsin, on 9 July 2008. Photo credit: National Weather Service-La Crosse.

Alistair MacEwen, a renowned British wildlife cinematographer, prepares to film mayfly nymphs at an improvised studio in Chaseburg, Wisconsin. Photo credit: Erik Daily, La Crosse Tribune.

Mayflies cling to the boat used by National Geographic Television cinematographers to film the insects’ emergence from the Upper Mississippi River the night before. Photo credit: USFWS.

Cinematographer Alistair MacEwen (left) and National Geographic Television producer John Benam (right) sort through an Upper Mississippi River benthos sample near Stoddard, Wisconsin, to collect mayfly nymphs for filming. Photo credit: USFWS.

Emergent mayflies accumulate knee-deep on an Upper Mississippi River bridge near Winona, Minnesota (circa 1960s). Photo credit: Calvin R. Fremling.

A Hexagenia mayfly nymph inhabits a U-shaped burrow it excavates in sediments composed of silt and clay in the Upper Mississippi River. Photo credit: Calvin R. Fremling.

As “Ol’ Man River keeps rollin’ along” through the heart of Upper Mississippi River (UMR) National Wildlife and Fish Refuge, the pulse of nature beats at a pace that changes seasonally as it has for millennia.  Amid broad landscapes of lush vegetation that frame an array of scenic river settings, an international group of award winning cinematographers has intermittently gathered here this year to film a variety of wildlife spectacles for a National Geographic Television production titled Planet in Motion.  While majestic bald eagles, graceful tundra swans, and brilliant neo-tropical songbirds are responsible, in part, for annually drawing an estimated 3.7 million visitors to this refuge to (re)connect with nature, Planet in Motion producer John Benam also wanted to highlight the vital ecological role played here by the deep-burrowing Hexagenia mayfly.  This small aquatic insect goes largely unnoticed throughout most of its year-long life cycle while it consumes decayed organic matter on the river bottom.  Later however, when they dramatically emerge from the water en masse, take flight and swarm to reproduce, mayflies become a widely available source of nutrition for a variety of omnivorous creatures that inhabit the refuge.  Cultural accounts of this apparent ephemeral existence, including the summertime use of snowplows to remove mayflies from bridges where they can accumulate knee-deep overnight, have been the subject of syndicated articles that have appeared in The New York Times and Ripley’s Believe It or Not.  In addition, some National Weather Service (NWS) offices now report the ability to detect large, distant swarms of mayflies with Doppler radar imagery when the insects emerge to mate.

To help plan and execute filming needs for the mayfly segment of this television production, Benam contacted La Crosse NFWCO biologist Mark Steingraeber in April.  Earlier in his Service career, Steingraeber published research on the bioavailability of sediment-associated contaminants to mayflies in the UMR and also helped the British Broadcasting Corporation film mayflies for a televised insect documentary.  Initially, Steingraeber provided detailed life-history and ecological information about the most common UMR mayfly species, H. bilineata.  He also assembled a list of key contacts, including staff at other local Service offices and businesses, who could provide additional assistance to the film crew.   Based on the fact that large numbers of emergent mayflies are often reported here during Fourth of July celebrations, the film crew was advised to plan for a large emergence during either the week preceding or the week following Independence Day.