About 700 volunteers from across the nation counted fireflies in their backyards, local parks and meadows and also noted their color and flash patterns.
The volunteers then entered their observations into an online database that's central to the Firefly Watch program sponsored by the Boston Museum of Science.
Scientists are worried by reports from the public that they are seeing fewer fireflies each summer, possibly because of habitat destruction from suburban sprawl.
About 5,100 people from 42 states and four other nations have taken part in Firefly Watch's online effort since it debuted in May 2008.
Editor's note: This one hour exposure photo taken June 22, 2009 and provided by Steve Irvine, captures fireflies in front of his home in Big Bay, Ontario in Canada.