The fungus Entomophthora muscae has a survival strategy that’s both fascinating and potentially deterring you from your next meal: It infects and “zombifies” female houseflies before sending irresistible chemical signals that encourage male houseflies to necrophilia.
By luring these male flies to mate with zombified females, the fungus can be transferred to the male fly and, in theory, has a better chance of dispersal. The unfortunate male fly is then taken by E. muscae in the same way.
Crucial to the process is the release of sesquiterpenes, or chemical messages, which are synthesized in the female corpse and sent as a seductive signal. According to experiments conducted by researchers, the longer the corpse has been dead, the more attractive it appears to males.
“The chemical signals act like pheromones that charm male flies and cause them to have an incredible urge to mate with lifeless female carcasses,” says evolutionary biologist Henrik H. De Fine Licht of the University of Copenhagen in Denmark. .
Once E. muscae has infected a female fly with its spores, it begins to multiply. After about six days, you can control the behavior of the insect, sending it to the highest possible point (on a wall or a plant) before it dies. Fungal spores are then sent off the dead fly, hoping to land on another.
But as this new study shows, by attracting a male, E. muscae can ensure that it moves on to at least one more host, which will once again carry its spores far and wide.
The team used a variety of chemical analyzes and genetic sequencing techniques to figure out exactly what the fungus was doing, as well as exposing male flies to female partners at different stages of fungal infection or who had died from other causes.
“Our observations suggest that this is a very deliberate strategy for the fungus,” says H. De Fine Licht. “He’s a true master of manipulation, and that’s incredibly fascinating.”
Tests showed that female fly corpses that had been dead for 3-8 hours attracted 15 percent of male flies, while with corpses that had been dead for 25-30 hours, that number skyrocketed up to 73 percent. The more time passed, the more chemical signals were released.
This is not the only time scientists have observed sesquiterpenes being used to attract the attention of insects. As chemical signals go, it appears to be one of the most effective at manipulating these tiny creatures.
There are many opportunities for further research here, particularly on effective fly repellents: flies can infect humans with various diseases, and sesquiterpenes could be used to attract flies away from certain areas, such as where food is prepared .
“This is where the fungus Entomophthora muscae can be useful,” says H. De Fine Licht. “It might be possible for us to use these same fungal fragrances as a biological pest control that attracts healthy males to a fly trap instead of a corpse.”
The research has been published in the journal ISME.