Massive mayfly emergence in Wisconsin is visible on weather radar

Animation of radar readings showing the huge cloud of mayflies emerging“The Mississippi River produced a massive radar echo as mayflies emerged from the water and became airborne. The mayflies were detectable on radar around 8:45 pm […] The radar loop below shows the reflected radar energy (reflectivity) from 8:35 pm to just after midnight. The higher the values (greens to yellows) indicate greater concentrations of flies.” (Source: NOAA)

Mayflies spend the majority of their life underwater, quietly eating algae and plant material. The full growth cycle of a mayfly can take up to 4 years; we just notice them when they pile up in post-coital exhaustion.

Mayflies emerge synchronously around dusk to avoid their main above-water predators: birds and bats. Predators trying to capitalize on a sudden mayfly all-you-can-eat buffet are overwhelmed by the emergence of millions of insects. Some individuals make it through, and the species continues.

Mayfly larvae are delightfully called “naiads,” and provide critical food for fish. The bodies of immature mayflies have beautiful external gills; this is also why they are important in assessing water quality. Mucky, polluted water is not a place a mayfly larva can breathe. Detroit has had mass mayfly emergences in the past, but a toxic algal bloom in Lake Erie this year is damaging populations of all the animals in the watershed. […]

“Mayflies are some of the most ancient insects around; they are well represented in Carboniferous fossils dating [more than] 300 million years ago. Fossil mayflies look remarkably like our modern mayflies; some consider them “living fossils.” The oldest fossil of a winged insect is a mayfly. (Source: Wired)

Gas pump covered in mayflies in the the Minnesota City and Trempealeau Area (Wisconsin, 2014)

(click thumbnails below to enlarge)