Evolutionary biologists Hassan Salem and Aileen Berasategui wondered what to make of a white, waxy material that builds up on juvenile tortoise leaf beetles (Chelymorpha alternans). The most common hypothesis posited that it was some kind of secretion, similar to what scale insects produce, but “it was showing up where it really shouldn’t,” says Salem, of the Max Planck Institute for Biology Tübingen in Germany.
Curious, they and their colleagues decided to investigate. “It was so surprising when we put the white substance on a petri dish, and then it grew,” says the University of Tübingen’s Berasategui. That test, which they performed in 2020, revealed the substance was microbial, but they didn’t yet know what kind of microbe it was, or whether it affected the beetles.
A subsequent analysis by the team, published today (August 19) in Current Biology, reveals the substance to be the fungus Fusarium oxysporum and documents ...
