Closer Look Florida Intertidal Firefly (Micronaspis floridana)

Many of our readers are native Floridians or have lived here for decades and remember when fireflies were a common sight in the evening. I remember when they seemed nearly as abundant as love bugs and never having to “look” for them because they were always visible in the yard during the summer nights. It seems the days of finding them in my own yard will remain a fond memory. In Florida, we have over 50 species of fireflies, many of which can still be seen in areas that have not yet suffered the disturbing influx of people relocating to Florida and consequential light pollution that limits the natural range of the firefly. Unfortunately, we have some species that are likely to become extinct entirely. This month we will take a closer look at the intertidal firefly (Micronaspis floridana) while this rare Florida treasure still exists.

Fireflies are not actually flies, but rather, beetles. It is a beetle known as the Florida Intertidal Firefly. This species is special because it is the only known species in the New World that inhabits salt water. True to the common name, it is found only in the intertidal zones of a short list of coastal salt marshes of Florida and a few northern islands of the Bahamas. The ideal habitat for this species is the mangroves, mudflats, and salt marshes we would normally associate with fiddler crabs and for that reason, these beetles are sometimes known as Fiddler Crab Fireflies.

Micronaspis floridana is a nocturnal member of the Lampyridae family of beetles and is related to click beetles and soldier beetles. The scientific name for this family of beetles comes to us from the Greek word “lampein” which means “to shine.” It is not the only beetle that shines with bioluminescence; there are over 2,000 species of fireflies worldwide and about 60 species in Florida alone.

The larva of the M. Floridana beetle is often called glowworms because they glow with bioluminescence just like the adults do. Larva can be found foraging for snails and slugs, along the high tide mark.

As adults, the glow is used to attract mates. The fireflies begin signaling 45-90 minutes after sunset. Males will announce themselves with short flashes every few seconds and females will respond with a long glowing flash lasting up to a minute sometimes synchronizing their response in small groups of three or four females. Though adults are active all year, they are most active from March through May.

The flash of the firefly is what fascinated me most about them as a child. I was one of those kids that caught them in a jar and could spend hours looking at them before finally releasing them again. The flash of the firefly is without question, the most important behavioral feature of this awe-inspiring beetle and critical for its survival. If fireflies can not see the glow of a potential mate, mating will not occur; and if mating does not occur, extinction is an inevitable consequence.

Unfortunately, local extinction of this species has already occurred throughout its historic range and the population that still remains has been fragmented to only seven known locations. There is reasonable concern that this fragmentation will not provide for the genetic biodiversity necessary for the species to survive. Coupled with the quality of the remaining locations suffering the impact of coastal development, light pollution, and increasing pesticide use, this species has been classified as endangered on the IUCN Red List, an authoritative source of detailed extinction risk of animal, fungus, and plant species.

I used to casually wonder why we don’t see as many fireflies in our neck of the woods as we used to. I no longer have to wonder because recent published studies provide the explanation. According to the state’s Office of Economic and Demographic Research and the latest Census Bureau data, more than 300,000 residents per year have relocated to Florida from other states since 2020 breaking records that date back to the 1940s and 1950s and bringing our Florida population to over 22 million.

In 2021 the International Union for Conservation of Nature (IUCN) published an assessment of the Florida intertidal firefly (Micronaspis floridana) and acknowledged it is to be considered “Endangered” and acknowledged that increasing pesticide use and habitat destruction are a major factor in this species diminishing populations however, light pollution may be the biggest culprit and this species is expected to continually decline.

Light pollution is a consequence of human population increases. As more people relocate to Florida, more light pollution results. Demand increases exponentially with every new resident for lighted consumer resources such as roadways, shopping centers, night-time entertainment, and more. The firefly can not compete with the light we produce with modern technology and consequently, has no option other than to migrate to a locale with less light pollution or perish and that’s exactly what is happening.

Although this species is listed as a “Species of Greatest Conservation Need” in Florida’s State Wildlife Action Plan (FFWCC 2012), to date there are no known conservation regulatory actions in place for this species. In March of 2023, the Xerces Society for Invertebrate Conservation petitioned Deb Haaland, Secretary, US Department of Interior to list Micronaspis floridana as an endangered species under the US Endangered Species Act, and a response is expected by June. By the time we reach the projected consequence of extinction, it will be too late for change and the species will transition from a natural wonder to a chapter in a natural history lesson. When you are out and about along coastal Florida this month, take a closer look for the intertidal firefly and if you don’t mind lending a helping hand you can get involved in citizen science efforts to report and track sightings of the intertidal firefly through the Firefly Atlas, (https://www.fireflyatlas.org/).