Periodical cicadas in 2017
In 2017, Populations of Brood VI emerged as expected, though they did so on slightly earlier calendar dates than during their previous emergence in 2000. Surprisingly, 2017 also saw significant straggler populations, mostly within the territory of Brood X, scheduled to emerge in 2021; these Brood X stragglers emerged after 13 years of development, not the usual 17 years. Though some of these straggler emergences were short-lived, others formed choruses and persisted for days or weeks. Even though internet reporting and news coverage makes it more likely than ever that such straggling events are detected and reported, the occurrence of so many stragglers in major metropolitan areas (as opposed to in wilderness areas) and the geographic range of these straggling events appears unprecedented and suggests that some general, regional influence may have triggered many cicadas to emerge off-schedule in different parts of the country.
The brief video below shows a timeline of Brood X straggler emergences in the Washington DC area in 2017.