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April 30, 2016

64 Degrees Fahrenheit Eight Inches Deep

Filed under: James Edward Heath,Magicicada,Periodical — Dan @ 1:22 am

hot under the exoskeleton

Soil temperature triggers periodical cicada emergences:

James Edward Heath in his paper Thermal Synchronization of Emergence in Periodical “17-year” Cicadas (Homoptera, Cicadidae, Magicicada)1 discovered that periodical cicadas will emerge, on average, when the soil 8 inches below the ground reaches 64 degrees Fahrenheit:

Soil temperature at 20-cm [7.87 in] depth in seven locations averaged 17.89 C [64.202 F] at the time of emergence, regardless of date. Cicadas emerging from burrows had average body temperatures of 18.04 C [64.472 F]. Synchrony in emergence may be due to animals reaching a critical threshold temperature.

The soil warms their bodies and that triggers the cicadas to emerge.

A warm rain, which will seep into the earth and warm the bodies of cicadas, can trigger a “particularly intensive” emergence.

Alexander and Moore (1962) noted that emergences were par- ticularly intensive following warm rains ( > 2 0 C ? ). I believe this suggests that the soil temperature probably was near emergence tem- perature and the heat transported by the water percolating into the ground warmed the soil sufficiently to raise soil temperature above the emergence threshold.

Some unanswered questions I have are: 1) how long does the temperature have to be 64°F+ – just a moment, or a certain number of hours, and 2) because we know not all cicadas emerge instantaneously, what is the maximum temperature that for certain will clear them from the soil?

This is an example of a temperature probe use to study the emergence temperature of cicadas. The probe in this picture is held by cicada researcher Gene Kritsky:
Temperature probe

Note that males typically emerge before females, and that the larger ‘decim species emerge before the smaller cassini species.

For a more modern, crowd-sourced study of this see the radiolab Cicada Tracker project.

I think I know what you’re thinking: “I don’t own a temperature probe, how can I guess when the temperature is 64°F 8” below the soil? Direct sunlight, air temperature and rain warms the soil. Southern facing land will warm sooner than northern facing land. Land in direct sunlight will warm faster than land in shade. Rainfall on a 80°+ day will quickly do the trick, but two weeks of temps in the 70°’s should work as well. So keep an eye on the 10-day weather forecast and watch for those days in the 70s, and especially the 80s.

Minimum Flight Temperature:
Their body temperature needs to be a little warmer than that to fly. Their minimum flight temperature (MFT) is 18-21°C / 65-70°F. The temperature varies depending on the Brood and species. They’ll need a few more degrees before they’re fully functional, and start singing and mating.

So, until their bodies are about 72°F (“room temperature”) they won’t be flying, singing and mating.

Maximum voluntary tolerance temperature:
Maximum voluntary tolerance temperature (MVT) for periodical cicadas is 31-34°C / 88-93°F, again depending on Brood and species. Maximum voluntary tolerance is the point at which cicadas seek shade and when thermoregulation takes precedence over other behaviors.

See Thermal responses of periodical cicadas: within and between brood parity (Hemiptera: Cicadidae: Magicicada spp.) and Thermoregulation by Endogenous Heat Production in Two South American Grass Dwelling Cicadas (Homoptera: Cicadidae: Proarna) for more information.

1 Thermal Synchronization of Emergence in Periodical “17-year” Cicadas (Homoptera, Cicadidae, Magicicada) by James Edward Heath, American Midland Naturalist, Vol. 80, No. 2. (Oct., 1968), pp. 440-448.

April 27, 2016

Please use the correct imagery for 17 year cicadas

Filed under: Identify,Magicicada,Periodical,Video — Dan @ 1:01 am

If you’re writing an article about the coming emergence of the 17-year periodical cicadas, please use the correct genus & species of cicadas.

The genus of all 17 year cicadas is Magicicada, and they are never green. The three species of 17-year cicadas are M. septendecim, M. cassini, and M. septendecula. They’re all black with orange wings and legs and red eyes (some exceptions, but they’re never green).

An adult Magicicada septendecim by Dan Mozgai/cicadamania.com:

Brood II Magicicada septendecim

A newly emerged, teneral, Magicicada septendecim by Dan Mozgai/cicadamania.com:

Imagining Brood II Magicicada septendecim

A mating pair of Magicicada septendecim by Dan Mozgai/cicadamania.com:

A pair of mating Magicicada septendecims found in Woodbridge Township NJ

17-year cicada video:

A singing Magicicada septendecim:

Singing Magicicada septendecim from Cicada Mania on Vimeo.

A Magicicada septendecim laying eggs:

Magicicada septendecim ovipositing from Cicada Mania on Vimeo.

A Magicicada septendecim up close (deceased):

Close up of a tymbal of a Magicicada septendecim from Cicada Mania on Vimeo.

Magicicada on a tree (mostly Magicicada cassini):

For the sake of cicada correctness, feel free to use them in your article. Just credit cicadamania.com.

More photos: All the Magicicada galleries on the site.

If you are looking to license Magicicada images or HD Video, Roy Troutman has plenty of both. Reach out to him if interested. His images and video are tagged throughout the site.

Hundreds of shed cicada skins (exuvia) by Troutman:

2014 Ohio Exuvia Pile by Roy Troutman

Wrong Cicadas:

If the cicada you use in your article is green, it isn’t a 17-year cicada. I repeat: if the cicada is green it is not a 17-year cicada.

The cicada at the top of the Wikipedia page for cicadas is not a 17-year cicada, it’s an annual cicada called Neotibicen linnei:

Tibicen linnei
(photo credit for this Neotibicen linnei).

The cicada shedding its skin on a roll of paper towel… that’s not a 17-year cicada either:

Wikipedia
(Photo Credits for the molting cicada).

Looking for people to speak at a conference or “cicadacon”?

Need a speaker for a Cicada Convention or a Periodical Cicada Event? Try these folks:

February 7, 2016

The Periodical Cicada Brood VII Revisited

Filed under: Brood VII,Magicicada,Periodical — Dan @ 9:22 pm

The Internet Archive has a lot of cicada documents and information, including a growing collection of articles from journals.

Today I came across a paper about Brood VII called The Periodical Cicada Brood vii Revisited (Homoptera, Cicadidae) by L. L. Pechuman, published in 1985 in the journal Entomology News (link to the article). Brood VII will be back in New York in 2018 (not too far away) so I’m glad I found this now. Brood VII is interesting because it is geographically isolated from other broods, near the Finger Lakes area of New York. This always makes me wonder what happened that led to their isolation (glacial melting, a massive die off of host trees… who knows).

The article is a quick, but melancholy read — unfortunately Brood VII is a small and dwindling brood; it has gone extinct in many areas, and has suffered over-predation by birds in recent emergences. “Populations were just not high enough to support ‘predator satiation'”, according to L. L. Pechuman.

People who witness massive periodical cicada emergences would never think that they were a fragile insect, but they are and papers like this make that fact abundantly clear.

November 24, 2015

Cicada Fun with Google Trends

Filed under: Australia,Brood X,Japan,Periodical,United States — Dan @ 7:59 pm

This article was inspired by Serious Fun with Google Trends by Simon Leather.

Google Trends is a Google website that lets you see trends in the search terms over time. When people search for “cicada” it usually means cicadas have emerged in their area at the time they search.

The following graph shows when people searched for “cicada” over the past 10 years in the United States. The largest spike, in May of 2004, coincided with the emergence of Brood X.

2004-2015

You might think that periodical cicada emergences cause the largest spikes, but not always — and not just because periodical cicadas don’t emerge every year.

2004: Cicada searches spiked May 16-22, which was Brood X – Magicicadas.
2005: Jul 31-Aug 6 spike which was for Neotibicen Cicadas. No periodical cicadas.
2006: Aug 13-19, Neotibicen Cicadas. No periodical cicadas.
2007: May 20-26, Brood XIII – Magicicadas.
2008: Brood XIV Magicicadas emerged (spike Jun 8-14), but the largest spike was Jul 29-Aug 2, Neotibicen Cicadas.
2009: Aug 16-22, Neotibicen Cicadas.
2010: Aug 8-14, Neotibicen Cicadas.
2011: May 29-Jun 4, Brood XIX – Magicicadas.
2012: Jul 29-Aug 4, Neotibicen Cicadas.
2013: May 5-11, Brood II – Magicicadas.
2014: Brood XXII – Magicicadas had a relatively small spike May 25-31, compared with Aug 24-30 for Neotibicen Cicadas (late season due to cool weather). There was also a teeny bit of a spike around January of 2014 due to the “cicada 3301” meme/game.
2015: Brood XXIII & IV Magicicadas emerged (spike around Jun 7-13), but the largest spike was around Aug 9-15 for Neotibicen Cicadas.

Which cities had the most cicada searches over the past 10 years? Cincinnati, Omaha, Nashville, Baltimore, Washington, Chicago, Alexandria, St. Louis, Philadelphia, and Charlotte. Time for me to move to Cincinnati!

How about Australia? Cicada searches in Australia spike in December. The largest spike was in December of 2013, which was indeed a big year for cicada emergences in Australia.

The variation year after year suggests that there is a degree of periodicity to Australian cicadas. There is always a spike around December, but some years see bigger spikes than others. Just speculation (partially because the 2004 & 2005 data seems absent) but perhaps there is a 9 or 11 year proto-periocity happening.

In terms of cities, Sydney has had the most cicada searches:

How about Japan?! August is the best month for cicadas (セミ) in Japan.

Yokohama, Chiba & Saitama generates the most cicada searches:

July 12, 2015

Why do Magicicada stay underground for 13 or 17 years?

Filed under: FAQs,Life Cycle,Magicicada,Periodical — Dan @ 8:01 pm

People ask: why do periodical cicadas stay underground for 17 or 13 years?

There are three parts to this puzzle that people are interested in:

  1. How cicadas count the years as they go by.
  2. Why prime numbers? 13 and 17 are prime.
  3. Why is their life cycle so long? They are one of the longest living insects.

Cicadas likely don’t count like people do (“1,2,3,4…”) and you won’t find scratch marks inside the cell (where they live underground) of a Magicicada, marking off the years as they go by. However, there is a kind of counting going on, and a good paper to read on that topic is How 17-year cicadas keep track of time by Richard Karban, Carrie A. Black and Steven A. Weinbaum. (Ecology Letters, (2000) Q : 253-256). By altering the seasonal cycles of trees they were able to make Magicicada emerge early, proving that cicadas “count” seasonal cycles, perhaps by monitoring the flow and quality of xylem sap, and not the passage of real time.

Why prime numbers, and why is the life cycle so long? This topic fascinates people. The general consensus is that the long, prime numbered life-cycle makes it difficult for an above-ground animal predator to evolve to specifically predate them. Read Emergence of Prime Numbers as the Result of Evolutionary Strategy by Paulo R. A. Campos, Viviane M. de Oliveira, Ronaldo Giro, and Douglas S. Galva ̃o (PhysRevLett.93.098107) for more on this topic. An argument against that theory is that a fungus, Massospora cicadina, has evolved to attack periodical cicadas regardless of their life cycle. Of course, a fungus is not an animal. Maths are easy for fungi.

There are also questions about why there are 13 and 17 year life cycles, why a 4 year acceleration of a brood might occur1 and why Magicicada straggle.

1 This is a good place to start: Genetic Evidence For Assortative Mating Between 13-Year Cicadas And Sympatric”17-Year Cicadas With 13-Year Life Cycles” Provides Support For Allochronic Speciation by Chris Simon, et al, Evolution, 54(4), 2000, pp. 1326–1336.

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