We had a lot of fun making naughty limericks up at the Bug Blog, but I thought people might be interested in the actual winner of the REAL Entomological Society of America (Not-At-All-Ribald-Please-Keep-It-Clean) Limerick contest. The winning limerick was not only clever, it illustrates an interesting relationship between two firefly species.
The Official ESA Winner:
Au Naturel Selection: Photinus meets Photuris
A firefly who was benighted
saw a light and became so excited–
he rushed to his fate
while selecting a mate:
lost his head, lost his heart, was de-lighted.
In case you aren’t familiar with the two genera of fireflies referenced in the limerick, their clever and deadly system of sexual mimicry was first described by Thomas Eisner. The flashes that attract males from the genus Photinus could be from female Photinus fireflies that want a hookup. But they could also be from the “Femmes Fatales” of the genus Photuris. They don’t want to have sex–they want to have a snack.
Photinus males aren’t just flashy dudes–they contain defensive chemicals in their blood. These chemicals repel predators like spiders. The Photuris females steal these chemicals from the males…by eating them. As you can see in the photos above, there isn’t much left when she’s done. Just some wings, like an empty candy bar wrapper.
The graph on the left is from tests of 29 females/group exposed to predator spiders–one group of females that had eaten Photinus males (“Fed”), and another group of females that haven’t had the special love bite (“Unfed”). Just eating two males is enough to completely protect the Photuris females from spider predators!
So pity the Photinus male; when out cruising for love, he must choose very, very carefully who he flashes.
You can read Eisner’s original paper here. I’m tempted to call it a “seminal” work.
Eisner T, Goetz MA, Hill DE, Smedley SR, & Meinwald J (1997). Firefly “femmes fatales” acquire defensive steroids (lucibufagins) from their firefly prey. Proceedings of the National Academy of Sciences of the United States of America, 94 (18), 9723-8 PMID: 9275191