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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New species: Luciola niah

Looks to be our second new species from the Sarawak CFZ holotype collected from Niah:

Luciola niah Jusoh sp. nov.

Figs 284–291

Type.Holotype male. MALAYSIA . SarawakLambir Hill24.ix.2010 , 19.24, Nazeri Abghani (SK0017 | MYFI018-14 ) ( FRIM ) Figs 284, 285, 288–291.

Paratypes . MALAYSIA . Sarawak : Kapit , I Polunin , no date 2 males ( ANIC ). Niah National Park forest track, M. Musbah and colleagues, 2.vii.2010 , 2 males (SK0023 | GenBank: KY572917.1, MF948239.1; SK0064). Long Aton, Ulu Baram, 2.ix.2011 , Musa Musbah 2 males (SK0067 | GenBank: MF063274.1; SK0069 | GenBank: MF063275.1) ( FRIM ) .

Diagnosis. 4.8–6.1 mm long; one of only two Luciolas. str. having dorsal colouration of yellowish brown with black elytral apices; other Luciolas. str. species with pale yellowish or pale brown pronota have dark brown to black elytra. Distinguished from the other similarly coloured species, L. jengaisp. nov. , most obviously by the abdominal colour in jengai , and which also does not have leaf like lobes on the inner margins of the LL.

Description of male. 4.8–6.1 mm long. Colour (Figs 284, 285): (Kapit males preserved in 70% ethanol differ in colour to remainder and are described here in brackets); pronotum yellowish with diffuse median darker markings (retraction of underlying fat body gives impression of darker markings); MN, MS and elytra yellowish brown with elytral apices black (elytra pale yellow with apices quite pale brown); elytra semitransparent and underlying hind wings may confuse interpretation of colour; head black, antennae and palpi dark brown (head reddish brown, antennae and palpi light brown); venter of thorax, basal abdominal ventrites and all abdominal tergites yellowish brown except for narrow dark posterior margin of V5 (all areas yellow except for thin dark marking on posterior margin of V5 ); legs yellowish brown with tibiae and tarsi dark brown (legs yellow, tarsi light brown); LO creamy white. Pronotum: slightly wider across middle (B> A, C); width a little less than humeral width; anterolateral corners angulate obtuse, posterolateral corners angulate. Elytron: subparallel sided. Head: minimal depression between eyes; GHW 11 X SIW; ASD much less than ASW (sockets are almost contiguous). Antennae: longer than GHW but not as long as 2 X GHW; segments elongate slender, scape longer than FS. Mouthparts: apical labial palpomere laterally flattened with inner edge dentate. Abdomen (Fig. 285): LO occupying entire area of V6 , 7; V7 a little longer than wide, posterior margin rounded and no MPP; T8 with anterolateral arms elongate slender slightly longer than entire posterior portion which is rounded and without median emargination. Aedeagal sheath (Figs 288, 289): apical margin of sheath sternite narrowly prolonged and medianly slightly emarginated and hairy; median anterior margin of sheath tergite strongly prolonged and apically pointed.Aedeagus (Figs 290, 291): apices of LL narrow; LL longer than ML and widely divergent.

Female : Jusoh associated the female by DNA barcode (Process ID: MYFI179-14 | GenBank: KY572915.1). Macropterous and capable of flight. Coloured as for male except for white LO restricted to V6 (Figs 286, 287). Bursa with two wide plates on each side.

Etymology . The locality name Niah is used as a noun in apposition.

Remarks . Ballantyne et al. (2016 Table 6 ) listed 30 species with this colour pattern (dorsally pale yellowish or pale brown with or without dark elytral apices) that is common among S. Asian Luciolinae . Many of these species have been assigned to species incertae here. Of the remainder the only species recorded from Sarawak having similar colouration is L. maculipennis Olivier , where the description of the terminal abdominal ventrite suggests a prolongation that could be typical of a Pygoluciola sp.

We have presently little information about shape and numbers of bursa plates in this genus. Paired plates as seen here are characteristic of other non-related genera like Pteroptyx and Colophotia . Luciola italica does not have bursa plates. Jusoh et al. (2018) scored this species as “ Luciola WFA”.