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July 5, 2015

What are Broods?

Filed under: FAQs,Magicicada,Periodical — Dan @ 6:29 pm

It is important to note that when we talk about cicada broods, we are talking about the 17 & 13 year periodical Magicicada cicadas. We are not talking about Tibicen or other species.

All Broods

There are 12 groups of Magicicadas with 17 year life cycles, and 3 groups of Magicicadas with 13 year life cycles. Each of these groups emerge in a specific series of years, rarely overlapping (17 & 13 year groups co-emerge every 221 years, for example). Each of these groups emerge in the same geographic area their parents emerged. These groups, each assigned a specific Roman numeral, are called broods.

Gene Kritsky’s book, Periodical Cicadas: The Plague and the Puzzle, documents the history of the recognition and naming of the broods. The first person to document that different groups of periodical cicadas emerged in different years was Nathaniel Potter in 1839. Benjamin D. Walsh and Charles V. Riley devised the system for numbering the different broods in 1868, and then C. L. Marlatt sorted the 17 year broods out from the 13 year broods, giving us the system we have today.

Visit our Broods page which features a grid of the Brood names, their life span, when & where they’ll emerge next and links to maps.


July 3, 2015

How Long Does a Periodical Cicada Emergence Last?

Filed under: FAQs,Magicicada,Periodical — Dan @ 2:47 pm

People often ask: “how long do cicadas last”, “how long will the cicadas be here”, or “how long do cicadas live above ground”?

People probably ask these questions, sadly, because they are tired of listening to the love songs of these cicadas. Like the saying “it is darkest before the dawn”, however, silence is typically a few weeks away.

The length of a local emergence:

The typical periodical cicada emergence will last between 6 to 8 weeks in a single location, with significant chorusing (singing) lasting about 3 to 4. Cool weather or rain can prolong an emergence.

The research paper Emergence of 13-Yr Periodical Cicadas (Cicadidae: Magicicada): Phenology, Mortality, and Predator Satiation by Kathy S. Williams, Kimberly G. Smith, and Frederick M. Stephen1 contains a wonderful study of the arc of a periodical cicada emergence. The entire emergence event takes place within 8 weeks, from the first emerged cicada to the last dead cicada (see Fig 4 in that document 1). The number of live adults reached its peak within two weeks, and then began to die off in significant numbers two weeks after that, due mostly to natural causes. After that the population of cicadas gradually dwindles due to natural deaths and predation.

Length of the chorusing:

Male cicadas will not begin chorusing at the start of an emergence, for a couple of reasons: 1) the first cicadas to emerge, which are primarily males (Fig 3 in 1), are mostly lost to consumption by predators (Fig 6 in 1), 2) Males can’t sing until their adult bodies are fully sclerotized, and 3) they need a significant number of males present before they will chorus. That said, chorusing typically begins within two weeks 2. Males will continue to chorus until enough cicadas die to no longer sustain the chorus, which is why the chorus lasts less than a month.

Length of the emergence of an entire brood:

An emergence spanning multiple states could last between 8 to 10 weeks from when the first cicadas emerge in the South to when the last cicada dies in the North. For example, Brood XXIII began appearing the second to last week of April in Mississippi, and there were likely some left in southern Illinois up until the last week of June.

References:

1 Kathy S. Williams, Kimberly G. Smith, and Frederick M. Stephen, Emergence of 13-Yr Periodical Cicadas (Cicadidae: Magicicada): Phenology, Mortality, and Predator Satiation, (1993), Ecology, Volume 74, Issue 4 (Jun., 1993), 1143-1152
2 Kathy S. Williams and Chris Simon, The Ecology, Behavior, and Evolution of Periodical Cicadas, (1995), Annu.Rev. Entomol. 40:269-95

June 27, 2015

What is Predator Satiation?

Filed under: FAQs,Magicicada,Periodical — Dan @ 9:24 pm

Why are there so many Magicicada periodical cicadas, and what does it have to do with the survival of their species? One of the answers is: Predator Satiation.

A predator is any animal that would eat a periodical cicada, i.e., birds, raccoons, squirrels, dogs, snakes, etc. Satiation, in the case of cicadas, means to supply predators with enough cicadas to eat until they are weary of eating and thus avoid them completely.

Predator satiation works like this:
1) Periodical cicadas emerge in tremendous numbers.
2) Adult cicadas are often timid, even after having sclerotized.
3) The first cicadas that emerge are eagerly consumed by predators.
4) The predators are so overwhelmed by the bounty of easily eaten cicadas, that they fill themselves to the point of disgust and exhaustion.
5) This gives the remaining cicadas a chance to escape the predators.

The first periodical cicadas are literally “fodder”, in the battle between predators and periodical cicadas, to use a war/video game analogy.

Look at this periodical cicada: it is thinking “hopefully this creature will eat me, so my siblings will live on!”

Magicicada on my finger by Dan from Cicada Mania on Vimeo.

The research paper Emergence of 13-Yr Periodical Cicadas (Cicadidae: Magicicada): Phenology, Mortality, and Predator Satiation by Kathy S. Williams, Kimberly G. Smith, and Frederick M. Stephen (Ecology, Volume 74, Issue 4 (Jun., 1993), 1143-1152) is worth reading if you are interested in this topic. They found that predation of cicadas peaks during the first few days of the emergence, and doesn’t resume in significant numbers until three weeks later (see figure 6, if you read the paper).

Unfortunately this strategy could be detrimental to periodical cicadas in areas with dwindling populations, where there isn’t enough of them to satiate the predators completely.

This strategy might also be used by other types of periodical cicadas like the Chremistica ribhoi of India, or cicadas that emerge in large numbers like Callogaeana festiva of south-east Asia.

What are stragglers?

Filed under: Accelerations,FAQs,Periodical,Periodical Stragglers — Dan @ 1:02 pm

Periodical cicadas often emerge in years before or after they are expected to emerge. When periodical cicadas don’t emerge on schedule we call them stragglers. Typically cicadas with a 17-year lifecycle will emerge 4 years early, and cicadas with a 13-year cycle will emerge 4 years late.

Probability of Straggling. Image courtesy of Chris Simon.
This image indicates the probability of Magicicada straggler emergences. Courtesy of cicada researcher Chris Simon.

People hear the word straggler and assume it means something that lags behind, but that is a laggard. A straggler can mean something that has deviated from an expected date/time or moved away from others of its kind. That said, periodical cicadas that emerge early can also be called precursors, but in scientific literature, they are called stragglers.

Visit Brood Chart to see when stragglers will be most likely.

Extremely likely stragglers in the next 10 years (or so):

2017: Brood X 4 years early.
2018: Brood XXII 4 years late.
2019: Brood XXIII 4 years late.
2020: Brood XIII 4 years early.
2021: Brood XIV 4 years early.
2025: Brood I 4 years early.

Accelerations

An acceleration occurs when periodical cicadas straggle in numbers significant enough to sustain future generations. In other words, a large population of a 17-year brood emerge in just 13 years, they avoid being eaten by predators, they mate and reproduce, and then 17 years later their off-spring emerge in large enough numbers to reproduce and sustain their population. This is one reason why two different broods might exist in the same area. 1

It is thought that Brood X was formed when a group of Brood XIV accelerated 4 years (they emerged in 13 years, rather than 17). Then Brood VI came from Brood X, and Brood II came from Brood VI. Brood XIV -> X -> VI -> II is called the “main sequence”1.

Accelerations may have been more prevalent and successful (successful in terms of sustaining future generations) in the past, when much of eastern North America was forests, and there was no human intervention or destruction of habitat to interfere.

References

1 Monte Lloyd & Jo Ann White. Sympatry of Periodical Cicada Broods and the Hypothetical Four-Year Acceleration. Evolution, Vol. 30, No. 4. (Dec., 1976), p. 795.

June 11, 2015

Look and listen for Magicicada stragglers in 2015

Another straggler sighting, this time in Cleveland which should make it a Brood V one year straggler:

Matt Berger Brood V Stragger 2
A Brood V straggler found by Matt Berger in West Virginia. See more photos of this cicada.

The emergence of Brood XXIII is well underway in the states along the Mississippi, and Brood IV should kick off in the west as soon as it stops raining every day. These aren’t the only Magicicada periodical cicadas emerging in the U.S. this year — some stragglers will emerge as well.

A straggler is a periodical cicada that emerges before or after the rest of its brood. Typically a straggler belonging to a 17 year brood will emerge 4 years early, but they might also emerge a year early, or a year late, or even 4 years late. This probability chart, details the probability of a straggler emergence.

In 2015 you might find the following stragglers:

  • Brood XIII 17 year cicadas emerging 4 years early in OH, PA, WVA.
  • Brood V 17 year cicadas emerging 1 year early in NY, OH, PA, VA, WVA.
  • Brood XIX 13 year periodical cicadas emerging 4 years late in AL, AR, GA, IL, IN, KS, KY, LA, MO, MS, NC, OK, SC, TN, VA
  • Brood XXII 13 year cicadas emerging a year late in LA, MS, OH, KY

Tyla MacAllister found a Brood XIX Magicicada straggler (emerged 4 years late) in Alabama!

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