In management training it usually goes like this. A monument in Washington is crumbling. Why? Harsh chemicals are used to clean it. Why? Pigeon droppings. Why so many pigeons? They eat the spiders. Why so many spiders? They eat the midges. Why so many midges? The monument is the first thing lit at dusk. Solution: turn the lights on an hour later.
Versions name the Washington Monument, the Jefferson Memorial or the Lincoln Memorial. In 2014 Joel Gross, writing on the lean-management blog The KaiZone, went looking for what actually happened, with help from the entomologist who did the work, Don Messersmith of the University of Maryland.
By Gross’s account, drawing on news reports of the time, the National Park Service hired consultants in 1989 for a year-long study of why the Lincoln and Jefferson memorials were deteriorating. The biggest threat to the marble turned out to be the sheer volume of water used to wash them. The Park Service cut back the washing and warned that the buildings might not look as white in future.
Why so much washing? Birds, starlings and sparrows rather than pigeons. But the bulk of it, Gross writes, was needed because of the midges. Tiny flying insects from the river, they swarmed at dusk, just as the floodlights came on. Dazzled by the lights, Alan Card later summarized, they flew into the walls and left them splattered with insects and their eggs. Spiders moved in to eat them, and birds came for the spiders.
In early 1990 the Park Service agreed to a six-week pilot. On Mondays, Wednesdays and Fridays, the lights went on an hour after sunset. Messersmith and a team of students counted the midges. On those nights there were about 85 percent fewer.
The research had found one thing drawing the midges, and a cheap fix. Messersmith’s later account, as quoted by Card, supplies the ending most retellings leave out. “But tourists who had driven hundreds of miles to have their photographs taken at the monuments were not happy. They complained every day, and the lights went back on.”