From the National Weather Service Weather Forecast Office, La…

From the National Weather Service Weather Forecast Office, La Crosse, WI:

Another Massive Mayfly Emergence!

The Evening of July 20, 2014

On an evening very similar to the massive mayfly event of June 23 2012, the Mississippi River produced a massive radar echo as mayflies emerged from the water and became airborne. The mayflies were detectable on radar around 845 pm and reports in the towns and cities began rolling in of the swarming and piles of mayflies. Numerous videos and pictures were circulating on social media, some of which are posted below as well.

The radar detected the flies about 845 pm, emanating from the river (the source) with echo values similar to that of light-moderate rain (35-40 dBZ). With a general south-to-north wind flow above the surface, the mayflies quickly moved north once in the air. As the flies dispersed moving north-northeast, they also gained altitude with some of the echo being detected as far north as Black River Falls and as high as 2500 feet above ground.

By late evening, mayflies were swarming in La Crosse, La Crescent, Stoddard and points up and down the river. While the emergence of mayflies from their river bottom mud dwelling can occur at various times through the warm season depending on the species, this particular emergence was that of the larger black/brown Bilineata species. The radar loop below shows the reflected radar energy (reflectivity) from 835 pm to just after midnight. The higher the values (greens to yellows) indicate greater concentrations of flies. Note how the swarm is carried northward over time.

Synchronized emergence of ephemeral adult stages is a beautiful thing. Mayflies (Ephemeroptera) are the best-known example, though there are others (like certain gall midges in Cecidomyiidae) that do it too.

They spend almost their entire lives as larvae. Then, on a particular night, they emerge as adults, mate, lay eggs, and die, all within the span of a few hours.

I wonder sometimes if the human affinity for dramatic stories that follow a certain narrative arc has its roots in this. The long, relatively slow build-up to a final climactic burst is something that has played out a million times in each of our evolutionary histories. Is it surprising that a story exhibiting the same pattern resonates emotionally?

Thanks to @bug_gwen on Twitter for bringing the weather radar gif to my attention.

Reposted from

Tags: insects, insects that anonsally will never see, very very very many insects, all on one night.

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