Seventeen Years Ago Today

Back in the spring of 2004, members of the Tri-County Conewago Creek Association (T.C.C.C.A.), a non-profit conservation group founded to improve water quality in Conewago Creek and its tributaries in Dauphin, Lancaster, and Lebanon Counties in Pennsylvania, were, in order to better understand the status of the flora and fauna in the watershed, frequently spending their weekends surveying the animal and plant life found in the drainage basin’s forests, streams, and farmlands.  This effort identified populations of several species of concern and helped supplement the more formal assessment that was used to determine the placement, scale, and scope of projects needed to reduce nutrient and erosion impairment in the Conewago’s waterways.

These regular outings happened to coincide with the Brood X Periodical Cicada emergence of 2004.  Back then, as the record keeper for the T.C.C.C.A.’s weekly survey forays, your editor decided to shade a map of the Conewago Creek Watershed showing where the group’s volunteers encountered choruses of the Brood X cicadas.  Fortunately, the map is still in the editor’s pile of stuff, and is reproduced here for you.

T.C.C.C.A.’s brochure map of the Conewago Creek Watershed (the Conewago east of the Susquehanna River), shaded with red ink in 2004 indicating locations where noisy choruses of Brood X Periodical Cicadas were found.  The range of the insects closely mirrors the forested areas of the watershed.  The nearly contiguous range along the southeast border includes the heavily wooded areas of Mount Gretna, State Game Lands 145, and the northwest slope of the diabase ridge that separates the Conewago from neighboring watersheds in Lancaster County.

A notation on the map (visible just above the cap on the pen) indicates May 16 as the emergence date for the cicadas in 2004—seventeen years ago today.

So why no seventeen-year cicadas yet in 2021?  The answer is ground temperature.  This year, by mid-April, Brood X Periodical Cicadas were just below the leaves and rocks, ready to break the surface.  But a cold month since then has stalled their emergence.  A thermometer pushed into the forest soil today showed readings of 60 degrees and less—at least four degrees below the temperature needed to get the nymphs crawling out of the dirt to climb rocks and vegetation where they’ll molt, dry, and take flight.

In the forested hills east of Conewago Falls, in the Conewago Creek Watershed, soil temperatures were as low as 54 degrees Fahrenheit today.

A warm week ahead with daytime temperatures in the eighties and nighttime lows in the fifties and sixties, instead of in the forties, should get the woodland soils warming.  Brood X Periodical Cicadas will be out and about in a jiffy—and you’ll hear all about it.

Coming up, The Great Eastern Brood.

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