The Enigmatic Blue Ghost Firefly Phausis reticulata (Coleoptera: Lampyridae): Observations on its Courtship, Mating and Oviposition Behaviors
Raphael De Cock1, Lynn Faust2 and Sara Lewis3 1 Evolutionary Ecology Group, University of Antwerp, Antwerp, Belgium 2 11828 Couch Mill Road, Knoxville, Tennessee, USA 3 Department of Biology, Tufts University, Medford, Massachusetts, USA
De Cock R., Faust L. & Lewis S. 2014. Courtship and mating in Phausis reticulata (Coleoptera: Lampyridae): male flight behaviors, female glow displays, and male attraction to light traps.
Florida Entomologist 97(4) in press.
Photo: Hugh Faust
Introduction
• Distribution: especially in forested regions of southern Appalachian Mountains, small populations as far west as Texas and Oklahoma
Introduction
• Distribution: especially in forested regions of southern Appalachian Mountains, small populations as far west as Texas and Oklahoma
TEXAS
OKLAHOMA
Introduction
• Distribution: especially in forested regions of southern Appalachian Mountains, small populations as far west as Texas and Oklahoma
• Habitat: generally in moist forested habitats with small streams or wetlands nearby, and soils overlain by a thick layer of leaf litter
Introduction
• Distribution: especially in forested regions of southern Appalachian Mountains, small populations as far west as Texas and Oklahoma
• Habitat: generally in moist forested habitats with small streams or wetlands nearby, and soils overlain by a thick layer of leaf litter
• Phenology - Peak mating season: “early season” (Apr-May ) “late season” (Jun-Jul)
Photo: Hugh Faust
Introduction
• Behavior: males of Phausis reticulata (Say) glow as they fly slowly over the forest floor
Introduction • Large numbers of these low-flying males create
remarkable and eerie display: this gave them their often heard local nickname: “Blue Ghost Firefly”
Photo: Blue Ghost Fireflies, by Spencer Black, North Carolina- NatGeo
Introduction • Recently, displays have become increasingly popular
as ecotourist attractions
Photo: Blue Ghost Fireflies, by Spencer Black, North Carolina- NatGeo
Introduction
• Male Phausis reticulata
Introduction
• Male Phausis reticulata
Introduction
• Male Phausis reticulata
Introduction
• Males of Phausis reticulata Say glow as they fly slowly over the forest floor searching for flightless females that are likewise bioluminescent
• strong sexual dimorphism:
♂: normal wings, fly ↔ ♀: neotenic, lack both elytra and wings
Introduction
• strong sexual dimorphism:
♂: normal wings, fly ↔ ♀: neotenic, lack both elytra and wings
Introduction
• strong sexual dimorphism: ♂: normal wings, fly ↔ ♀: neotenic , lack elytra and wings • Because of the female’s appearance: “Appalachian glow-
worm”
Introduction
• strong sexual dimorphism: ♂: normal wings, fly ↔ ♀: neotenic, lack elytra and wings • Because of the female’s appearance: “Appalachian glow-
worm” • Females have several spot-like light organs whose glow is
visible ventrally and dorsally through the transparent cuticle
Introduction
• Previous work described – Morphology (Fender 1966), – Geographic distribution (Lloyd 1965, 2004; Frick-Ruppert
& Rosen 2008) – Seasonal and nightly activity patterns (Frick-Ruppert &
Rosen 2008) – Preliminary observations on courtship behaviors (Lloyd
1965 ) and mating (Frick-Ruppert & Rosen 2008)
Introduction
• Previous work described – Morphology (Fender 1966), – Geographic distribution (Lloyd 1965, 2004; Frick-Ruppert &
Rosen 2008) – Seasonal and nightly activity patterns (Frick-Ruppert &
Rosen 2008) – Preliminary observations on courtship behaviors (Lloyd
1965 ) and mating (Frick-Ruppert & Rosen 2008)
• Surprisingly little work has been done on P. reticulata courtship, mating behavior, oviposition patterns.
Introduction
• Previous work described – Morphology (Fender 1966), – Geographic distribution (Lloyd 1965, 2004; Frick-Ruppert &
Rosen 2008) – Seasonal and nightly activity patterns (Frick-Ruppert &
Rosen 2008) – Preliminary observations on courtship behaviors (Lloyd
1965 ) and mating (Frick-Ruppert & Rosen 2008)
• Surprisingly little work has been done on P. reticulata courtship, mating behavior, oviposition patterns.
• Some authors suggest that pheromones might play a role (Lloyd 1965, 1997a, 1997b, 2004; Frick-Ruppert & Rosen 2008),
Introduction
• Previous work described – Morphology (Fender 1966), – Geographic distribution (Lloyd 1965, 2004; Frick-Ruppert &
Rosen 2008) – Seasonal and nightly activity patterns (Frick-Ruppert &
Rosen 2008) – Preliminary observations on courtship behaviors (Lloyd
1965 ) and mating (Frick-Ruppert & Rosen 2008)
• Surprisingly little work has been done on P. reticulata courtship, mating behavior, oviposition patterns.
• Some authors suggest that pheromones might play a role (Lloyd 1965, 1997a, 1997b, 2004; Frick-Ruppert & Rosen 2008),
but no extensive experimental proof
Introduction
Aims
Aims
Provide additional insight into the reproductive ecology of this enigmatic and rather atypical firefly species:
Aims
Provide additional insight into the reproductive ecology of this enigmatic and rather atypical firefly species: • Study field populations: observations about courtship, copulation,
oviposition behavior
Aims
Provide additional insight into the reproductive ecology of this enigmatic and rather atypical firefly species: • Study field populations: observations about courtship, copulation,
oviposition behavior • controlled field experiments to investigate courtship signals,
including the relative importance of possible pheromones and bioluminescent glows
Aims
Provide additional insight into the reproductive ecology of this enigmatic and rather atypical firefly species: • Study field populations: observations about courtship, copulation,
oviposition behavior • controlled field experiments to investigate courtship signals,
including the relative importance of possible pheromones and bioluminescent glows
• Additionally report: – Spectrum of bioluminescence of P. reticulata – variation in female light organ patterns – detailed descriptions of copulation and oviposition – female egg guarding
• Fieldwork 4-19 Jun 2011 and 15-26 Jun 2013 (second mating peak)
• On several locations within Great Smoky Mountains National Park: West side of Burnt Mountain (730 m), near Park Headquarters (475 m), on the north side of Sugarlands Mountain (845 m), NW flank of Mount LeConte (946 m)
General Material & Methods
Nightly flight activity of males
Result
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Males’ reactions to many different types of glow sources: • Attracted to dimly glowing light sources small dots of phosphorescent paint small Betalights or breaklights
• Not to stronger light sources (LEDs, 9V lightbulbs, other firefly flashes)
Male Search Behaviors
Result
Males’ reactions to many different types of glow sources: • Attracted to dimly glowing light sources small dots of phosphorescent paint small Betalights or breaklights
• Not to stronger light sources (LEDs, 9V lightbulbs, other firefly flashes)
Male Search Behaviors
Result
Males’ reactions to many different types of glow sources: • Attracted to dimly glowing light sources small dots of phosphorescent paint small Betalights or breaklights
• Not to stronger light sources (LEDs, 9V lightbulbs, other firefly flashes)
Male Search Behaviors
Result
Males’ reactions to many different types of glow sources: • Attracted to dimly glowing light sources small dots of phosphorescent paint small Betalights or breaklights
• Not to stronger light sources (LEDs, 9V lightbulbs, other firefly flashes)
Male Search Behaviors
Result
Males’ reactions to many different types of glow sources: • Attracted to dimly glowing light sources small dots of phosphorescent paint small Betalights or breaklights
• Not to stronger light sources (LEDs, 9V lightbulbs, other firefly flashes)
Male Search Behaviors
Result
Overflying males often circle back to inspect fainter light sources: • flew around 10-15 sec • at ~ 20 cm height • moving in small circles or spirals ~10 to 80 cm in diameter • often “jitterbugging” and “spotlighting” • some eventually drop directly onto or within 2 cm of the
glowing source
Male Search Behaviors
Result
Observations on male search behavior and glow lures suggest: • More likely to inspect and land on lures closely
resembling P. reticulata female glow patterns
Male Search Behaviors
Result
Observations on male search behavior and glow lures suggest: • More likely to inspect and land on lures closely
resembling P. reticulata female glow patterns • No detection or no response to female-like glows beyond
1 m distance
Male Search Behaviors
Result
Observations on male search behavior and glow lures suggest: • More likely to inspect and land on lures closely
resembling P. reticulata female glow patterns • No detection or no response to female-like glows beyond
1 m distance • Approaches and landings only during peak male activity
(21:45-22:00): later males seem to ignore glow lures
Male Search Behaviors
Result
Female Size
Female body size was highly variable, and we found a 3-fold difference in size measured as pronotal area
Female Size
Result
Variation among Phausis reticulata females in the number, size and position of light spots
Female Display
Result
Schematics showing variation and asymmetry in light spot patterns among 14 “late season” female Phausis reticulata observed in Jun 2011 and 2013 from the GSMNP. Small type females 5-6mm (a- c) bear 3 to 4 light organs; Large type females 8-12mm (d-n) show 6 up to 9 lanterns.
Female Display
Result
Schematics showing variation and asymmetry in light spot patterns among 14 “late season” female Phausis reticulata observed in Jun 2011 and 2013 from the GSMNP. Small type females 5-6mm (a- c) bear 3 to 4 light organs; Large type females 8-12mm (d-n) show 6 up to 9 lanterns.
Female Display & Size
Result
Schematics showing variation and asymmetry in light spot patterns among 14 “late season” female Phausis reticulata observed in Jun 2011 and 2013 from the GSMNP. Small type females 5-6mm (a- c) bear 3 to 4 light organs; Large type females 8-12mm (d-n) show 6 up to 9 lanterns.
Female Display & Size
Result
Female Display & Size
Result
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# Glow spots
Pearson r = 0.78, p = 0.007
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0.8
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Pro
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# Glow spots
Pearson r = 0.78, p = 0.007
Female Display & Size
Result
Q: Are P. reticulata males more strongly attracted to females with a greater number of glow spots?
Male Attraction and N° ♀ Glow Spots
Q: Are P. reticulata males more strongly attracted to females with a greater number of glow spots?
• Field experiments artificial light lures mounted in traps
(Jun 2013) • Data: number of trapped males as an estimate for the
attractiveness of a glow display • N = 12
Method
Male Attraction and N° ♀ Glow Spots
? <
5 males 20 males (binomial P = 0.002)
Result
<
Male Attraction and N° ♀ Glow Spots
5 males 20 males (binomial P = 0.002)
However possible violation of assumption of independent trials: glows of trapped males attract additional males into traps?
Result
? <
Male Attraction and N° ♀ Glow Spots
5 males 20 males (binomial P = 0.002)
However possible violation of assumption of independent trials: glows of trapped males attract additional males into traps? Re-analysis with more conservative approach considering only catch success per trap
Result
? <
Male Attraction and N° ♀ Glow Spots
5 males 20 males (binomial P = 0.002)
Result
4/12 traps 8/12 traps 33% capture success 66% capture success
? <
Male Attraction and N° ♀ Glow Spots
<
5 males 20 males (binomial P = 0.002)
Result
4/12 traps 8/12 traps 33% capture success 66% capture success (Fisher’s Exact P = 0.2)
? <
Male Attraction and N° ♀ Glow Spots
? <
Conclusion
Male Attraction and N° ♀ Glow Spots
Inconclusive though highly suggestive evidence that males prefer displays with more light spots
Courtship Signals: Glows and Pheromones
Q: What is the relative importance of possible pheromones vs. bioluminescent glows ?
• Field experiment (Jun 2013) • Live field-collected P. reticulata females • Compare the number of males attracted to 3 treatments:
Method
Courtship Signals: Glows and Pheromones
3 treatments: 1. GLOW (n=5) : sealed with an airtight transparent cover
Method
Courtship Signals: Glows and Pheromones
3 treatments: 1. GLOW (n=5) : sealed with an airtight transparent cover 2. GLOW + PHEROMONE (n=6) : mesh cover allowing female’s glow and possible sex pheromones to disperse (closest to natural condition)
Method
Courtship Signals: Glows and Pheromones
3 treatments: 1. GLOW (n=5) : sealed with an airtight transparent cover 2. GLOW + PHEROMONE (n=6) : mesh cover allowing female’s glow and possible sex pheromones to disperse (closest to natural condition)
Method
Courtship Signals: Glows and Pheromones
3 treatments: 1. GLOW (n=5) : sealed with an airtight transparent cover 2. GLOW + PHEROMONE (n=6) : mesh cover allowing female’s glow and possible sex pheromones to disperse (closest to natural condition) 3. PHEROMONE (n=7) : mesh cover allowing any possible sex pheromones + cardboard shield preventing males from seeing female’s glow
Method
Courtship Signals: Glows and Pheromones
Comparison females’ success in attracting males (landed yes/no): PHEROMONE (n=7): 57% GLOW (n=5): 60% GLOW+PHEROMONE (n=6): 100%
Result
Courtship Signals: Glows and Pheromones
Comparison females’ success in attracting males (landed yes/no): PHEROMONE (n=7): 57% GLOW (n=5): 60% GLOW+PHEROMONE (n=6): 100% Freeman-Halton exact two-tailed p = 0.2
Result
Courtship Signals: Glows and Pheromones
Proportion of overflying males that landed directly on or within 1 m of females (mean + 1 SE)
Result
Courtship Signals: Glows and Pheromones
Proportion of overflying males that landed directly on or within 1 m of females (mean + 1 SE)
Result
Courtship Signals: Glows and Pheromones
Two-way ANOVA: NS
Bioluminescence Emission Spectrum
P. reticulata emission spectrum maximum wavelength male = 552 nm; female max. wavelength = 547 nm.
Result
Bioluminescence Emission Spectrum
Mating
VIDEO mating behavior
Result
Mating
• Mean copulation duration (± SE) : 7.9 ± 1.3 min (n = 5)
Result
Mating
• Mean copulation duration (± SE) : 7.9 ± 1.3 min (n = 5)
• Small females (<6mm, 4 or less glow spots) were ignored even after antennal contact !
Result
Mating
• Mean copulation duration (± SE) : 7.9 ± 1.3 min (n = 5)
• Small females (<6mm, 4 or less glow spots) were ignored even after antennal contact !
• Females polyandrous: mated females show typical glow display on subsequent nights and remate with new males in captivity
Result
Mating
Oviposition Behaviors
After ovipositing, females (n = 4) curl their bodies tightly around their eggs, using one or more legs to grasp them.
Result
Oviposition Behaviors
Conclusions
Conclusions
New insights into the courtship signals and mating behavior
Conclusions
New insights into the courtship signals and mating behavior • Phausis reticulata obstacle-filled habitats with dense
understory: may favor evolution of mixed signaling systems that use a combination of pheromones (long-range attraction) and bioluminescence (short-range localization)
Conclusions
New insights into the courtship signals and mating behavior • Phausis reticulata obstacle-filled habitats with dense
understory: may favor evolution of mixed signaling systems that use a combination of pheromones (long-range attraction) and bioluminescence (short-range localization)
• Our experiments provide additional suggestive, though inconclusive, evidence that female-produced pheromones may play a role in P. reticulata courtship
Conclusions
Signaling system much more complex than previously thought: • Begin flight activity: primarily focus on female light
signals ?
Conclusions
Signaling system much more complex than previously thought: • Begin flight activity: primarily focus on female light
signals ? • Later perhaps switching to pheromones at lower
densities of unmated females (pheromone plumes more distinct OR unmated females might release pheromone only later at night) ?
Conclusions Novel evidence that P. reticulata males could use female courtship glows as an honest signal of female reproductive potential: • Across many insects, female body size is correlated with
fecundity
Conclusions Novel evidence that P. reticulata males could use female courtship glows as an honest signal of female reproductive potential: • Across many insects, female body size is correlated with
fecundity • Extensive variation in P. reticulata female body size
Conclusions Novel evidence that P. reticulata males could use female courtship glows as an honest signal of female reproductive potential: • Across many insects, female body size is correlated with
fecundity • Extensive variation in P. reticulata female body size • Size positively correlated with number light spots in female
glow display
Conclusions Novel evidence that P. reticulata males could use female courtship glows as an honest signal of female reproductive potential: • Across many insects, female body size is correlated with
fecundity • Extensive variation in P. reticulata female body size • Size positively correlated with number light spots in female
glow display • Suggestive evidence from glow lure experiments that males
prefer displays with more light spots
Conclusions Novel evidence that P. reticulata males could use female courtship glows as an honest signal of female reproductive potential: • Across many insects, female body size is correlated with
fecundity • Extensive variation in P. reticulata female body size • Size positively correlated with number light spots in female
glow display • Suggestive evidence from glow lure experiments that males
prefer displays with more light spots • overall brightness or glow spot pattern that plays a role ?
New research questions • Need for more detailed research on complex mixed
signaling strategies in this and other glow-worm fireflies
New research questions • Need for more detailed research on complex mixed
signaling strategies in this and other glow-worm fireflies
• Characterize pheromones + examine possible effects of female age, mating status, environmental conditions
New research questions • Need for more detailed research on complex mixed
signaling strategies in this and other glow-worm fireflies
• Characterize pheromones + examine possible effects of female age, mating status, environmental conditions
• Single species or a complex of several species or subspecies? 2 seasonal peaks + occurrence of ignored small 4-spotted vs. larger females with >6 glow spots
New research questions • Need for more detailed research on complex mixed
signaling strategies in this and other glow-worm fireflies
• Characterize pheromones + examine possible effects of female age, mating status, environmental conditions
• Single species or a complex of several species or subspecies? 2 seasonal peaks + occurrence of ignored small 4-spotted vs. larger females with >6 glow spots
• Function of male glow ?
New research questions • Need for more detailed research on complex mixed
signaling strategies in this and other glow-worm fireflies
• Characterize pheromones + examine possible effects of female age, mating status, environmental conditions
• Single species or a complex of several species or subspecies? 2 seasonal peaks + occurrence of ignored small 4-spotted vs. larger females with >6 glow spots
• Function of male glow ? - Hypothesis: male glow triggers female glow = not
supported
Thanks for listening
… any questions?
Acknowledgments
We thank the organisors of the 2014 International Firefly Symposium to offer this chance to share our results. Becky Nichols and Adriean Mayor of the GSMNP for guidance, help and assistance. Raphael De Cock was funded in 2011 by a research grant from the Research Foundation Flanders (F.W.O. file K2.064.11N) and thanks Erik Matthysen for support and advice. We thank Patti Edwards, Kathrin Stanger-Hall and Sarah Sander for their enthusiastic company, assistance and support during 2011 field trips, Henri Tellegen of OceanOptics Inc. for advice on spectrophotometry, Tristan Mooij (Betalight b.v., The Netherlands) for providing information and solutions with Betalights. Special thanks to Zach Kobrinsky and David Liittschwager, on assignment for National Geographic Magazine for housing and help in 2013. This study was performed with the necessary permits (Permit numbers: GRSM-2011-sci-0017, GRSM-2013-sci-0096).
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