FIREFLY FEMMES FATALES ACQUIRE DEFENSIVE STEROIDS (LUCIBUFAGINS) FROMTHEIR FIREFLY PREY

Female fireflies of the genus Photuris, the so-called firefly ''femmes fatales,'' prey on male fireflies of the genus Photinus. The females are able to entrap the males by faking the flash signal characteristic s of the Photinus female. We found that by feeding on Photinus males, Photuris females gain more than nutrients. They also acquire defensive steroidal pyrones called lucibufagins, which are contained in Photinu s but which Photuris fireflies are unable to produce on their own. Pho turis females that eat Photinus males or lucibufagin are rejected by P hidippus jumping spiders. Lucibufagin itself proved to be a deterrent to such spiders. Field-collected Photuris females contain lucibufagin in varying amounts. The more lucibufagin they contain the more unaccep table they are to Phidippus.