A deadly case of beer goggles

Photo credit: Darryl Gwynne/earthtimes.org

Male jewel beetles are literally dying to mate with brown beer bottles in Australia. The orange-brown coloration and manner of light reflection from dimples in the bottles resemble female jewel beetle wing covers, or "elytra". 

University of Toronto professor Darryl Gwynne and colleague David Rentz  observed this behavior while conducting field work alongside a road littered with the bottles. The bottles may act as "supernormal releasers", or exaggerated stimuli that evoke an instinctive behavioral response. In this case, the males may view the bottles as "super females" and will mate with them at all costs. These relentless mating attempts often result in death by overheating in the sun or through predation by ants. This week Gwynne and Rentz were awarded an Ig Nobel prize at Harvard University for their discovery, which was originally documented in 1983. 

Besides the mild humor involved, the discovery highlights one of the many ways that littering can adversely affect wild populations, such as the mating system of a beetle species.

Learn more about Dr. Darryl Gwynne's research:

http://labs.eeb.utoronto.ca/gwynne/

Killer Beetle Babies

Watch out, because what you eat can kill you! At least this is what Gil Wizen and Dr. Avital Gasith (Tel-Aviv University, Israel) discovered when observing interactions between amphibians and ground beetle larvae (Genus Epomis).  In an extraordinary case of predator-prey role reversal, some Epomis species have evolved anti-predator behaviors that enable them to deceive and devour their much larger would be predators. These beetle babies subsist solely on amphibians, such as frogs and salamanders, and exploit their predatory instincts by moving their antennae and mandibles, presenting themselves as tasty treats. As the unsuspecting victim is lured in, the larva heightens the excitement by flailing it's appendages more vigorously until the amphibian goes in for the kill.

Epomis larva luring a prey item through movement of antennae and mandibles. Video credit: Gil Wizen.

The tables are soon turned, however, as the larva stealthily avoids the frog's protracting tongue and harpoons the animal with hooked jaws, latching on tightly. The predator will then "suck the life" out of it's prey, ingesting bodily fluids followed by the tissues. In many instances, only bones are left behind. Those able to escape the clutches of the larvae are literally scarred, bearing the marks of being "hooked".

 Amphibian metamorph attempting to ingest an Epomis larva. Photo credit: Gil Wizen.

Leftovers. Photo credit: Gil Wizen.

Wizen and Gasith performed 382 trials where Epomis larvae and various amphibians "faced off" in test arenas. In 100% of the interactions, the beetle larvae were successful in subduing their prey, even if they were initially ingested by the amphibian! These findings have been featured in a great article published in PLoS ONE.

Predator-prey role reversal in action. Video credit: Gil Wizen.

Once the beetles have matured, they exhibit a more varied diet, however, amphibians are still not safe. Adult Epomis beetles are known to immobilize their amphibian prey with a paralyzing bite before ingesting them alive.