Monday, May 28, 2012


Every seventeen years, eastern Pennsylvania experiences the emergence of a strange group of insects in the genus Magicicada, the periodic cicadas. After spending most of the time in the ground, millions of cicadas emerge synchronously and enter the adult life stage. The adult male cicadas fly to the treetops where they sing, looking for mates. At times, densities of over one million periodic cicadas per acre have been recorded, which creates an incredibly loud noise of over 100 decibels from the forest floor.

Magicicada sp.

The Magicicada broods that emerge in this region are known as "Brood II," which extends from northern North Carolina to southern Massachusetts and "Brood XIV," which can be found from northern Alabama to Massachusetts. Throughout the eastern United States, there are sixteen (plus one extinct) distinct broods that differ in emergence year and geographic location. Most of these groups live on a seventeen-year cycle, but some (especially in the southern portion of the country) emerge every thirteen years.

Brood XIV last showed up in 2008. However, the emergence did not quite reach Monroe County where I live.

2008 Brood XIV from CicadaMania

The last emergence of Brood II was in 1996 which means that next year should be the year when these cicadas fill the forests of this area! Since I was only about a year old when the cicadas were out in 1996, I have never experienced the impressively large number of cicadas that are present on emergence years. However, some Magicicadas mess up and emerge on the incorrect year. The closer the year gets to a large emergence year, more "stragglers" begin to emerge and sing.

Since 2013 will be a big year, I have noticed quite a few periodic cicadas in the woods around my house. Their unique sound is hard to miss in the woods and their brightly colored bodies are difficult to ignore when walking through the forest. I have also encountered a number of these cicadas in the field, where they perch on blades of grass.

The color pattern is difficult to mistake!

It is important to note that there are cicadas that emerge every year. These "annual cicadas" make up the majority of the cicada species that occur in this region. In Pennsylvania, the annual cicadas do not usually begin calling until July. The songs of these species are very different from that of the periodic cicadas and the coloration is completely different. Most annual cicadas are colored black and green rather than black and orange.

Swamp Cicada (Tibicen tibicen), an annual cicada
Dark Lyric Cicada (Tibicen lyricen engelhardti), an annual cicada

When you are in the woods, keep and eye and and ear out for these awesome insects and look forward to next year when they will be everywhere and we can all enjoy this incredible evolutionary phenomenon.

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