Turning your host into a zombie that encourages males to have sex with its corpse may sound like an odd way to ensure your survival, but that is exactly what a parasitic fungus in the United States does. It turns out that female goldenrod soldier beetles, when infected with the fungus Eryniopsis lampyridarum, do everything possible to encourage males to have sex with their dead bodies.
Usually found feeding on the tops of flowers in meadows and fields across North America, the researchers analyzed over 400 live and dead goldenrod soldier beetles, and found that around 20 percent of the insects were infected with the fungus. Weirdly, many of the dead infected females were displaying the same unusual pose.
After making the beetles climb to the tops of the flowers, and then gripping onto it with their mandibles, the fungus made the females spread their wings out and puff their abdomen up.
The strange thing is that after studying the beetles as they succumbed to the infection in real life, the researchers found that this pose was actually struck sometime between 15 and 22 hours after the fungus had killed the insects. It is thought that the fungus in effect reanimates the corpse of the host, making it stretch out its wings and inflate its abdomen.
The researchers suspect that by gripping tight to the top of flowers – where most healthy beetles are foraging for food and looking for mates – and then the spreading of the wings and enlarging of the abdomen makes the zombie females more appealing to the opposite sex, in turn, encouraging healthy males to land on the dead females and mate, a behavior that was indeed observed in the wild. The spores are then transferred to the males, assisting in the spread of the fungus.
Despite sounding like something straight out of science fiction, this parasite is grounded very firmly in reality. There are hundreds, if not thousands of parasites known to high-jack their host, infecting their minds and altering their behavior. One of the most well-known is cordyceps, a fungi that infiltrate the bodies of a range of insects, such as ants, and makes them climb to a high spot before grabbing tight as the fruiting body erupts out of the head and showers spores down on the colony.
Published in the Journal of Invertebrate Pathology, the researchers describe how the fungus attempts to spread its spores through the population of beetles, and how the beetles are manipulated into doing its bidding.