A Global Perspective on Firefly Extinction Threats

Authors:

SARA M. LEWIS , CHOONG HAY WONG, AVALON C.S. OWENS , CANDACE FALLON, SARINA JEPSEN, ANCHANA THANCHAROEN, CHIAHSIUNG WU, RAPHAEL DE COCK, MARTIN NOVÁK, TANIA LÓPEZ-PALAFOX, VERONICA KHOO, AND J. MICHAEL REED

Firefly beetles (Coleoptera: Lampyridae) show great diversity in their ecology, behavior and extinction risk factors. (a) Photinus pyralis adults of both sexes are capable of flight, but populations across the eastern United States still show restricted gene flow (photograph: Terry Priest). (b) Dispersal is even more limited in the glowworm fireflies such as Lampyris noctiluca, whose females (right) are flightless (photograph: Zdeněk Chalupa). (c) All firefly larvae are predatory, and many are dietary specialists; L. noctiluca shown attacking Helix aspersa (photograph: Heinz Albers). (d) Massive courtship aggregations and synchronous flashing inspire ecotourism, which can lead to habitat degradation (Pteroptyx malaccae in Thailand, photograph: Radim Schreiber).



Insect declines and their drivers have attracted considerable recent attention. Fireflies and glowworms are iconic insects whose conspicuous bioluminescent courtship displays carry unique cultural significance, giving them economic value as ecotourist attractions. Despite evidence of declines, a comprehensive review of the conservation status and threats facing the approximately 2000 firefly species worldwide is lacking. We conducted a survey of experts from diverse geographic regions to identify the most prominent perceived threats to firefly population and species persistence. Habitat loss, light pollution, and pesticide use were regarded as the most serious threats, although rankings differed substantially across regions. Our survey results accompany a comprehensive review of current evidence concerning the impact of these stressors on firefly populations. We also discuss risk factors likely to increase the vulnerability of certain species to particular threats. Finally, we highlight the need to establish monitoring programs to track long-term population trends for at-risk firefly taxa.

Keywords: Coleoptera, extinction risk, insect conservation, IUCN, Lampyridae

Since their evolutionary origin some 297 million  years ago (Zhang et al. 2018), beetles have been highly successful; they represent 38% of known insect species (Stork 2018). Fireflies (Coleoptera: Lampyridae) rank among the most charismatic beetles, with distinctive bioluminescent courtship displays that make them a potential flagship group for insect conservation. With more than 2000 species worldwide, firefly beetles exhibit surprisingly diverse life history traits (figure 1; Ohba 2004, Lloyd 2008, Lewis 2016), including nonluminous adults with daytime activity periods, glowworm fireflies with flightless females, and lightning bugs that exchange species-specific flash signals. Fireflies also inhabit ecologically diverse habitats, including wetlands (e.g., mangroves, rice paddies, marshes, desert seeps), grasslands, forests, agricultural fields, and urban parks. Their predaceous
larvae, which can be aquatic, semiaquatic, or terrestrial, spend months to years feeding on snails, earthworms, and other soft-bodied prey. In contrast, firefly adults are typically short lived and do not feed. Some taxa are habitat and dietary specialists, whereas others are ecological generalists
(Reed et  al. 2020). Fireflies are economically important in many countries, because they represent a growing ecotourist attraction (Napompeth 2009, Lewis 2016). However, as is true for many invertebrates (Cardoso et  al. 2011), fireflies have been largely neglected in global conservation efforts.

Monitoring studies that provide quantitative data on population trends are lacking for almost all firefly species.

However, surveys have revealed significant recent declines in the mangrove firefly Pteroptyx tener in Malaysia (Jusoh and Hashim 2012, Khoo et al. 2014) and in the glowworm Lampyris noctiluca in England (Gardiner 2011, Atkins et  al. 2017). Anecdotal reports and expert opinion also suggest reductions in both the occurrence and abundance of many firefly species over recent decades (Lewis 2016, Faust 2017, Lloyd 2018).

In 2010, an international group of firefly experts convened in Malaysia and wrote The Selangor
Declaration on the Conservation of Fireflies (Fireflyers International Network 2012), recommending actions to preserve these iconic insects. In 2018, the IUCN (International Union for Conservation of Nature) Firefly Specialist Group was established to assess the conservation status and extinction risks to fireflies worldwide. As part of this effort, in the present article we discuss perceived threats to firefly biodiversity and persistence on the basis of an opinion survey of experts from different geographic regions. We also review the current evidence for the impact of such threats on firefly
populations. Finally, for each threat, we discuss associated risk factors (sensu Reed et al. 2020)—that is, behaviors and life history traits that make certain species especially vulnerable to particular threats.

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