The results are preliminary, to be sure. More tests are planned, naturally. But here it is so far:

Midges don't like what they can't see.

They are harmless, mosquito-like creatures that would be unworthy of national concern except that they have developed a fondness for the Lincoln and Jefferson memorials. As spring slides into summer, they emerge at dusk from the Potomac River, see the monuments bathed in light and proceed to slime the national heritage.

Worried not only by unsightly midge leavings but by wear-and-tear on marble from repeated cleanings, the National Park Service commissioned a test that began in April to see if altering the memorials' lighting would make a difference.

Because midges are crepuscular -- that is, active primarily at dusk -- Donald H. Messersmith, an entomologist at the University of Maryland, theorized that if the lights were not turned on until well after dark, the problem would cease because the midges would be abed by then.

So, on Mondays, Wednesdays and Fridays from April 16 to May 28, the floodlights were not turned on until about an hour after sunset. On Tuesdays, Thursdays and weekends, the lights came on at 6 p.m., the regular time. Each weeknight, Messersmith and two students counted the number of midges that landed in four one-meter squares they had marked on the walls of both the Jefferson and Lincoln memorials.

Result: a total of 49 midges at the Lincoln Memorial on the nights when lighting was delayed, and a total of 510 when it was not. At the Jefferson, 52 midges overall on the delayed-lighting nights, 264 on the regular-lighting nights.

Prof. Messersmith?

"It leads us to conclude that there is a definite influence on the midges when the lights are off. They are not attracted as much . . . . There were many nights when there were no midges at all."

But he's not scientifically convinced, not yet.

Because many nights were unusually cold, Messersmith said, the midges probably were not as active as they usually are. He plans to repeat his light test from July 30 to Aug. 24, when the nights will be warmer and the midges will be as active as normal.

Still, delayed lighting seems to be the answer: "I'm very encouraged."