Locusts are crop pests of biblical proportions. They can form swarms of thousands upon thousands of insects, which fly from place to place consuming every shred of greenery in their path. Finding a way to effectively stop the swarms from forming in the first place, therefore, is a multi-national priority, with high economic stakes.
Enter the grasshopper gut parasites. In 2004, Chinese researchers first noticed that locusts infected with the parasite Paranosema locustae tended not to swarm, ScienceNOW reports, and researchers recently revisited the locust-parasite relationship, uniting those organisms in the lab. ScienceNOW:
The parasite acidified the locusts’ lower guts, subduing the growth of bacteria responsible for creating the pheromones. Additionally, the researchers found that infected locusts produced lower levels of the neurotransmitters serotonin, which can initiate swarming behavior, and dopamine, which can sustain the behavior.
In additional experiments, the team found that non-infected locusts did not respond to infected locusts' poop—which is used as a chemical signalling cue—as they normally would, either, confirming that the physiological changes did indeed have an impact on insect behavior.
While ScienceNOW points out that microbes alone probably won't be enough to stop a swarm (locusts also use physical contact to trigger swarming behavior, not just chemical signals), this could be a helpful tool to make locust plagues a thing of the past.