130: Western Fireflies

Today’s animal feels like a cryptid – a species that is rumored to be in Colorado but very rarely observed, tracked to remote locations and a remnant of a population from a time with a different climate regime. This is the western firefly, which is neither a fly, nor a bug, but a beetle, from the family Lampyridae (you can probably guess what that means). Colorado has several species of fireflies, including two luminescent ones (Photuris spp., Photinus pyralis). The non-luminescent species of firefly are much more common in Colorado, especially in the eastern part of the state.

The luminescent populations live in isolation, along waterways that are often shaded with cottonwoods, leftover groups from when Colorado was a wetter place thousands of years ago. Human agricultural activities that changed the movement of water across the landscape from the 19th century until today may have wiped out some of these remnant populations, but manmade irrigation channels also may provide refugia for them. They have been confirmed to live in Weld, Larimer, Boulder, Adams, Pueblo,

Yuma, Routt, Alamosa and Saguache counties, with anecdotal reports that they are spread widely over the Western Slope and were once in Denver too.

Fireflies are predators that hunt snails, slugs, and soft-bodied insects in moist grassy areas. Larvae overwinter in Colorado and then become adults for the summer, being most abundant in June and July. The luminescent ones have a special organ that they use to produce light: “Light production occurs from

combination of the compound luciferin with the enzyme luciferase. Oxygen, ATP and water are also needed to achieve the light producing chemical reaction and light flashing is precisely regulated, with each species producing unique light flash patterns. These are used to locate mates, with males and females each producing different flashes. (Non-luminescent species are presumed to used chemical cues - sex pheromones - for mate recognition.)”

Some readers will know (one in particular) that there are lots of plants and animals that occur in children’s literature written by authors from either Europe or the east coast of North America that I simply did not believe were real as a child growing up in the southwest. Fireflies were very high on that list. I did not know there are fireflies in Colorado until a few days ago when I read this beautiful story about the quest to document them by Andrew Kenney of Colorado Public Radio News. The story talks about the effects that climate change, and the resultant aridification of the west, may have on our native fireflies. I really hope to be able to see them sometime!