A fungus produces an amphetamine-like stimulant in cicadas

Insect-killing fungi usually kill the host before releasing spores. Massospora is one of the few exceptions: it keeps the insect alive and moving while the rear of the abdomen is replaced by a solid plug of spores. The insect keeps flying and courting, spreading the infection — a strategy known as active host transmission.

In 2019 Greg Boyce's team published in Fungal Ecology the result of a metabolomic search through such infections. In four populations of periodical cicadas infected by Massospora cicadina they detected cathinone, an amphetamine known until then from the khat shrub. In annual cicadas infected by Massospora platypediae or Massospora levispora, which are probably a single species, they found psilocybin, the compound associated with Psilocybe mushrooms.

The most interesting part is what they failed to find. The Massospora genomes lack some of the enzymes needed for the known biosynthetic routes to cathinone and psilocybin, and neither the expected intermediate metabolites nor the gene orthologs could be detected. The authors infer cautiously that the fungus may make these compounds by another, undescribed route — not that it inherited a ready-made pathway from a plant or another fungus.

The tempting conclusion that "the fungus drugs the insect so it will spread spores" is a hypothesis, not a demonstrated mechanism. We know both compounds are neuroactive in other animals, and we can see that infected cicadas behave differently. What is missing is the experiment linking the two causally. The paper describes a very strong circumstantial case and says plainly that it is circumstantial.

The behavioural change itself is well documented, and it is unnervingly precise. John Cooley and colleagues reported in Scientific Reports in 2018 that male cicadas carrying the conidiospore-producing stage of the infection perform precisely timed wing-flick signalling — a signal normally given only by sexually receptive females. That draws healthy males into close contact, and the contact apparently spreads the infective spores. Males with the second stage of infection, which produces resting spores waiting for the next cicada generation, do not give the female signal.

Neither periodical cicadas nor Massospora occur in Polish forests, but their relatives do. Fungi in the order Entomophthorales kill flies, aphids and moths, and dead insects glued to grass stems with their wings spread are the commonest trace of them. The same pattern — a parasite that arranges its host in a position convenient for its own spores — has appeared repeatedly and independently in fungal evolution.

What the evidence actually shows

Chemically, the compound is not amphetamine but cathinone, a natural stimulant with a β-ketoamphetamine structure. Metabolomics detected cathinone in four populations of periodical cicadas infected by Massospora cicadina. Annual cicadas infected by the M. platypediae/levispora lineage contained psilocybin instead, with psilocin in some samples. The parasite replaces the rear abdomen with a spore mass, yet the host remains mobile and continues sexual interactions that spread the fungus. The study demonstrated the compounds’ presence; it did not administer purified cathinone to healthy cicadas or prove that this molecule alone causes a particular behaviour. Its possible role in maintaining activity or altering appetite remains a hypothesis. A scientifically safer title is therefore “a fungus produces an amphetamine-like stimulant in cicadas,” without implying deliberate dosing or a completed causal experiment.