Fig 2. Schematic of Massospora–cicada infection cycle.

This schematic shows the known and possible modes of infection for cicadas infected with Massospora spp. adapted from previous studies on the natural history of this fungal genus [8,13,24,25]. In this figure, the conidial infection is shown in a male for simplicity, but both males and females exhibit conidial infections. Red arrows indicate stages at which cicadas are infected with the fungus, and uncertain routes of infection, with potential significant impacts on the inoculation and spread, are labeled with “?”. Estimates for incubation periods (dashed arrows) for both conidia (typically beginning late May) and resting spore stages (typically first observed in mid-June) are based on the examination of 198 M. cicadina-infected periodical cicada specimens and 1,236 iNaturalist observations (accessed 16 March 2020) spanning 1974–2019 across 29 states in the mid-Atlantic US. Data for Massospora specimens spanned from Texas to Connecticut, with the earliest specimen collected from Mississippi in early May, about a month before they are first found in the northeast.