Every week, Bob Lyon volunteers at the Smithsonian Naturalist Center in Leesburg. He helps catalog and identify various species of moths. In 1990, Lyon, a retired civil engineer, said he felt a moral obligation to take a closer look at and catalog the various plants and creatures in Loudoun County. He began by identifying and listing more than 900 species of plants before moving on to mammals, amphibians, reptiles and then to his passion, insects -- especially moths.

Photo: Bill Snead, LoudounExtra.com

Every week, Bob Lyon volunteers at the Smithsonian Naturalist Center in Leesburg. He helps catalog and identify various species of moths.

Photo: Bill Snead, LoudounExtra.com

Bob Lyon is holding a Catacala moth. Each week, he volunteers at the Smithsonian Naturalist Center in Leesburg where he helps catalog and identify various species of moths.

Photo: Bill Snead, LoudounExtra.com

This moth is an Io moth, or Anisota, in the Smithsonian's Nature Center in Leesburg. Bob Lyon volunteers at the center each week.

Photo: Bill Snead, LoudounExtra.com

Sitting in front of the walnut mantle he built from a fallen tree, Bob Lyon records the numbers that correspond with moth photographs he's taken. Lyon lives five miles southwest of Purcellville.

Photo: Bill Snead, LoudounExtra.com

Bob Lyon sits in the living room of his rural Loudoun County home while he talks about his collection of moth photographs. Lyon is 87 years old.

Photo: Bill Snead, LoudounExtra.com

The book shelves in Bob Lyon's living room extend for much of one wall. Here, he is going through his box of index card looking for a particular catalog.

Photo: Bill Snead, LoudounExtra.com

Bob Lyon writes numbers next to the names of moths he has identified that will correspond with his index card filing system.

Photo: Bill Snead, LoudounExtra.com

Bob Lyon often must look through catalogs and collections of moth drawings to correctly identify specimens.

Photo: Bill Snead, LoudounExtra.com

Bob Lyon walks across the back yard of his rural Loudoun County home.

Photo: Bill Snead, LoudounExtra.com

Bob Lyon with a black rat snake he found in his back yard. After taking photographs of the snake, it slithered away. Lyon lives five miles southwest of Purcellville.

Photo: Bill Snead, LoudounExtra.com

In 1990, Bob Lyon, a retired civil engineer, said he felt a moral obligation to take a closer look at and catalog the various plants and creatures in Loudoun County. He began by identifying and listing more than 900 species of plants before moving on to mammals, amphibians, reptiles and then to his passion, insects -- particularly moths. Lyon, 87, lives five miles southwest of Purcellville.

Photo: Bill Snead, LoudounExtra.com

Bob Lyon holds a black rat snake. He nearly stepped on the snake while walking across his back yard. Lyon lives near Purcellville.

Photo: Bill Snead, LoudounExtra.com

Bob Lyon photographs a black rat snake in his back yard. Lyon, 87, lives five miles southwest of Purcellville.

Photo: Bill Snead, LoudounExtra.com

A black rat snake hangs on to a small tree branch, allowing Bob Lyon to get a better photograph of the reptile.

Photo: Bill Snead, LoudounExtra.com