February 2014 Featured Paper
"Shunning the Night to Elude the Hunter: Diurnal Fireflies and the ‘Femmes Fatales’"
Chemoecology 16 (2006): 39-43
Matthew Gronquist1, Frank C. Schroeder2, Helen Ghiradella3, David Hill4, Erin M. McCoy1, Jerrold Meinwald2, and Thomas Eisner5
1Department of Chemistry, SUNY, Cortland, NY 13045, USA 2Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA 3Department of Biology, SUNY, Albany, NY 12222, USA 4213 Wild Horse Creek Drive, Simpsonville, SC 29680, USA 5Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
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Many fireflies, including those in the genus Photinus and Lucidota, contain poisonous chemicals called lucibufagins (LBGs) in their blood. These LBGs protect the fireflies against most predators, but not against the so-called “femmes fatales” fireflies in the genus Photuris. Photuris fireflies do not produce LBGs themselves and must acquire them by preying on Photinus. Lucidota are active only during the day, and so they avoid similar predation because they do not encounter the nocturnal Photuris.
Lucidota adults contain vestigial light organs, suggesting that their ancestors were nocturnal. This study presents evidence that, had they remained nocturnal, they would have been preyed upon by Photuris for their LBGs, and that Lucidota evolved a daytime lifestyle as a means to avoid this predation.
Four questions are explored in this study:
Do the LBGs in Lucidota’s blood protect them from predation?
Lucidota fireflies were offered to four types of predators: wolf spiders, jumping spiders, orb web spiders, and a thrush. In each instance, the predator rejected the Lucidota. The LBGs in the blood of Lucidota appear to offer them protection from predation.
Will Photuris attack and eat Lucidota?
In each test in which a Lucidota was offered to a Photuris, the Photuris attacked and devoured the Lucidota in the same manner that Photuris attacks Photinus.
Is Photuris able to sequester and use LBGs gained from Lucidota?
Blood collected from Photuris that had not been fed a Lucidota was devoid of LBGs, while blood collected after feeding showed the presence of LBGs, indicating that Photuris is able to sequester the LBGs from Lucidota.
Do Photuris actively seek out insects that contain LBGs?
When offered both a Lucidota and a control insect without LBGs in their blood, the Photuris always attacked and devoured the Lucidota. Only one of the control insects was attacked but only partially devoured.
When offered a pair of mealworms, one coated with LBGs and one without, the Photuris investigated only the coated mealworms; however, none of the mealworms were bitten.
The tests in this study were conducted with Lucidota atra, a firefly known to contain LBGs. Other species of Lucidota (L. punctata and L. luteicollis) might also be expected to contain LBGs and enjoy the same benefits of a daytime lifestyle as L. atra. One might want to apply this argument to other daytime fireflies as well, including those in the genus Ellychnia and Pyropyga. However, although it has been shown that Ellychnia is rejected by predators, the presence of LBGs in these fireflies remains unknown.
While it is not possible to say conclusively that Lucidota were driven to adopt a diurnal lifestyle by predation pressure from Photuris, the findings in this study support the idea. Evidence suggests that Photuris seek out insects containing LBGs. By developing a daytime lifestyle, Lucidota avoids this predation while still retaining the protection from other predators afforded by their LBGs.
The argument put forth here that Lucidota evolved a diurnal lifestyle to avoid a nocturnal predator may apply to other insects as well. It is known, for instance, that butterflies evolved from moths. Moths developed the ability to avoid bats with the development of ears sensitive to the ultrasonic sounds bats produce. Butterflies did not evolve this feature, and to avoid predation by bats were in effect “driven” to a diurnal lifestyle. It has been said that, in a sense, bats “invented” butterflies. In the same way, it can be said that Photuris fireflies may have “invented” Lucidota and other diurnal fireflies.
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