A New Periodical Cicada Puzzle

by Carl Strang

I have been getting questions from people asking about periodical cicadas this year. They have been hearing reports of brood XIX, the simultaneous emergence of several species of 13-year cicadas to the south of our area. I have been giving the sensible answer that no, we won’t be getting them in northeast Illinois. That was up until Tuesday afternoon, when I heard three periodical cicadas singing on the Mayslake Forest Preserve mansion grounds.

The songs were those of Cassin’s periodical cicada. This is a photo from the 2007 main emergence in our area. The insect on the right is a Cassin’s 17-year cicada, the one on the left is our other local species, Linnaeus’ 17-year cicada.

But that wasn’t all. That same day I heard another singing cicada half a county away from Mayslake, at forest preserve district headquarters. Then yesterday I heard individuals at two more locations on the Mayslake preserve, and two in west central DuPage County, where there were very few scattered individuals in 2007. Furthermore, I have heard reliable reports of singing periodical cicadas in other DuPage County locations.

I don’t see any way to connect this to the 2007 emergence. True, a few late cicadas came out in 2008 (I called them Oops Cicadas), but that is to be expected. There were none in 2009 or 2010. The question I would like to have answered first is whether these are 13-year or 17-year cicadas. There is a 13-year species with the same song as cassini. I hope I can get specimens, a shed nymphal exoskeleton at least. That could be held for potential future DNA checking. This would establish whether these might be outliers of brood XIX. The thing is, most people don’t listen for singing insects. We don’t really know what is going on with periodical cicadas outside of peak emergence years or core emergence areas. If I learn anything new, I’ll pass it on, but I will try to get as many location observations as I can in the limited time I have to devote to this unexpected development.

1 Comment

  1. June 27, 2011 at 6:07 am

    […] In an earlier post I speculated about what was going on with these cicadas, which had been quiet the previous two years. A suggestion by WBEZ radio news director and nature enthusiast Brian O’Keefe reminded me of similar ideas expressed in the scientific literature when cicadas appear outside their brood’s normal area: perhaps these were transported from the southern brood XIX range in the root balls of nursery stock. That certainly could account for the ones in residential areas and in portions of forest preserves adjacent to private lands. I checked with the Forest Preserve District of DuPage County’s nursery staff, however, and none of our tree plantings in the past 13 years have come from so far south. Some of these cicadas are half a mile or more from the nearest preserve boundary. A little mystery therefore remains, but I have concluded that my time would be better spent in other directions. […]

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