When reporting the event in a paper that a Swedish academic journal published in 1756, Kalm described documents (including one that he had obtained from Benjamin Franklin) that had recorded the presence of large numbers of these insects in 1715 and 1732.
When reporting the event in a paper that a Swedish academic journal published in 1756, Kalm wrote: The general opinion is that these insects appear in these fantastic numbers in every seventeenth year. Kalm then described documents (including one that he had obtained from Benjamin Franklin) that had recorded the presence of large numbers of these insects in 1715 and 1732.