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Magicicada Mapping Project Homepage

A National Geographic Society sponsored project

The periodical cicadas (Magicicada spp.) of Eastern North America have the potential to answer general questions concerning speciation, species boundaries, and postglacial biogeography. Many of these questions are most effectively addressed with accurate maps of periodical cicada emergences. Yet although crude maps of periodical cicadas have existed for over a century, many current maps of these insects are only modernizations of these earlier maps, and their inaccuracies or errors limit their utility.

custom datalogger

Modern transportation, highly accurate base maps, GPS technology, and a better understanding of periodical cicada biology provide unprecedented opportunities for accurately mapping Magicicada populations. To date, we have surveyed and mapped over 10,000 localities within periodical cicada emergences, using detailed base maps and GPS technology, such as the custom GPS datalogger pictured below. To learn more about the equipment used in this study, follow this link.

custom datalogger

Why map periodical cicadas?

Periodical cicada emergences capture popular attention. When European colonists first encountered these insects, they were puzzled. Emergences seemed unpredictable, and over the years, the insects appeared to move across the landscape as if they were plagues of locusts.

In response to this confusion, natural historians began to record the dates and locations of emergences. Early efforts to compile this information into maps demonstrated that there was a clear, predictable pattern to emergences: In any given area, adult periodical cicadas emerge only once every 13 or 17 years, they are consistent in their life cycles, and populations (or "broods") in different regions are not synchronized.

Currently there are 7 recognized species, 12 distinct 17-year broods, and 3 distinct 13-year broods, along with 2 known extinct broods, found east of the Great Plains and south of the Great Lakes, to the Florida Panhandle. From this bewildering mix, several patterns have emerged:

  1. Most of the complex spatial and temporal relationships of periodical cicada broods and species must be less than 10,000 years old, because much of the current range of periodical cicadas in the eastern, Appalachian, and Midwestern U.S. would have been unsuitable for periodical cicadas during and for substantial periods following the Wisconsin glaciation (see Watts 1983; Webb 1981).

  2. Permanent life cycle changes lead to species formation, while temporary life cycle changes lead to brood formation in Magicicada. Each Magicicada species is most closely related to another with a different life cycle, a pattern that suggests multiple speciation events involving permanent life cycle change (Cooley et al. 2001; Marshall and Cooley 2000; Marshall et al. 2003; Simon et al. 2000). By contrast, environmental miscues of life cycles have the potential to form broods without permanently altering life cycles (Kritsky and Simon 1996; White and Lloyd 1979; Young 1958).

  3. Geographic distributions hold the key to understanding life cycle change in Magicicada. One instance of allochronic speciation, the formation of the 13-year species M. neotredecim from the 17-year species M. septendecim was identified on the basis of a striking biogeographic pattern of reproductive character displacement (Cooley et al. 2001; Marshall and Cooley 2000; Simon et al. 2000). The temporal and biogeographic relationships of 17-year broods suggest a scheme in which geographically adjacent broods are more closely related than distant broods (Alexander and Moore 1962; Marlatt 1923; Young 1958) and in which broods gave rise to other broods via simple 1- or 4- year temporary life cycle accelerations (Lloyd and Dybas 1966; Simon and Lloyd 1982).

Although maps are an important tool for addressing such questions, most current distribution maps of periodical cicadas trace their ancestry to C. M. Marlatt’s (1923) 19th century compilations of historical emergence records. Unfortunately, these maps and their derivatives tend to overestimate periodical cicada range limits, so they can provide misleading answers to important questions (Marshall 2001). The questions involved are not trivial: Periodical cicada responses to deglaciation may provide insights into the possibility that they are useful for monitoring forest and ecosystem health (see Cooley et al.; Cooley et al. 2004), while the biogeography of broods and species may provide critical insights into the general nature of species, speciation processes, and gene flow between species.

Preliminary results may be seen by searching the Magicicada database.

  • Alexander, R. D., and T. E. Moore. 1962. The evolutionary relationships of 17-year and 13-year cicadas, and three new species. (Homoptera: Cicadidae, Magicicada). University of Michigan Museum of Zoology Miscellaneous Publication 121:1-59.

  • Cooley, J. R., D. C. Marshall, and K. B. R. Hill. Periodical Cicada Brood XI is extinct (manuscript).

  • Cooley, J. R., D. C. Marshall, and C. Simon. 2004. The historical contraction of periodical cicada Brood VII (Hemiptera: Cicadidae: Magicicada). Journal Of The New York Entomological Society 112:198-204.

  • Cooley, J. R., C. Simon, D. C. Marshall, K. Slon, and C. Ehrhardt. 2001. Allochronic speciation, secondary contact, and reproductive character displacement in periodical cicadas (Hemiptera: Magicicada spp.): genetic, morphological, and behavioural evidence. Molecular Ecology 10:661-671.

  • Kritsky, G., and S. Simon. 1996. The unexpected 1995 emergence of periodical cicadas (Homoptera: Cicadidae: Magicicada spp.) in Ohio. Ohio Journal Of Science 96:27-28.

  • Lloyd, M., and H. S. Dybas. 1966. The Periodical Cicada Problem. II. Evolution. Evolution 20:466-505.

  • Marlatt, C. 1923. The Periodical Cicada. United Stated Department of Agriculture, Bureau of Entomology Bulletin 71

  • Marshall, D. C. 2001. Periodical cicada (Homoptera: Cicadidae) life-cycle variations, the historical emergence record, and the geographic stability of brood distributions. Annals Of The Entomological Society Of America 94:386-399.

  • Marshall, D. C., and J. R. Cooley. 2000. Reproductive Character Displacement and Speciation in Periodical Cicadas, with Description of a New Species, 13-Year Magicicada neotredecim. Evolution 54:1313-1325.

  • Marshall, D. C., J. R. Cooley, and C. Simon. 2003. Holocene climate shifts, life-cycle plasticity, and speciation in periodical cicadas: A reply to Cox and Carlton. Evolution 57:433-437.

  • Simon, C., and M. Lloyd. 1982. Disjunct synchronic population of 17-year periodical cicadas: Relicts or evidence of polyphyly? Journal of the New York Entomological Society 110:275-301.

  • Simon, C., J. Tang, S. Dalwadi, G. Staley, J. Deniega, and T. R. Unnasch. 2000. Genetic Evidence for Assortative Mating between 13-Year Cicadas and Sympatric "17-Year Cicadas with 13-Year Life Cycles" Provides Support for Allochronic Speciation. Evolution 54:1326-1336.

  • Watts, W. A. 1983. Vegetational history of the eastern United States 25,000 to 10,000 years ago. Pp. 294-310 in H. E. Wright and S. C. Porter, eds. Late Quaternary Environments of the United States. University of Minnesota Press, Minneapolis.

  • Webb, T. I. 1981. The past 11,000 years of vegetational change in Eastern North America. Bioscience 31:501-506.

  • White, J., and M. Lloyd. 1979. 17-Year Cicadas Emerging After 18 Years: A New Brood? Evolution 33:1193-1199.

  • Young, F. N. 1958. Some facts and theories about the broods and periodicity of the periodical cicadas. Proceedings of the Indiana Academy of Sciences 68:164-170.
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