Study
How 17-year cicadas keep track of time
Karban, Richard; Black, Carrie A.; Weinbaum, Stephen A.
Ecology Letters, 2000
Periodical cicada nymphs were transplanted onto peach trees whose flowering schedule was manipulated so that the trees flowered twice within a single year, doubling the seasonal signal available in the sap the nymphs feed on. Emergence timing was then compared against nymphs on unmanipulated trees.
- Studied in
- Magicicada
- Sample size
- cicada nymphs on experimentally manipulated trees
Nymphs on trees forced to flower twice in one year emerged a year early. The nymphs appear to track the annual cycle of their host tree rather than counting time directly, so doubling the tree’s apparent years advanced the cicadas by one.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Periodical cicadas time their emergence by counting annual cycles in the host plant, rather than by an internal clock running independently of the environment.
How NatureHQ reads it
This is a rare experiment on an animal that reproduces once every seventeen years, and it converts an unanswerable question into a partly answered one. The nymph is not counting years; it is counting something the tree does once a year, which is a much cheaper mechanism and also a fragile one. It leaves the harder half untouched — knowing how a nymph counts to seventeen is not the same as knowing why seventeen.
- Small numbers, and an experiment that is extremely difficult to repeat on this timescale.
- Shows that the host cycle can shift emergence, not that it is the only input.
- Says nothing about why the count is 13 or 17 rather than any other number.
Tricking a tree into two years, and watching the cicadas believe it
A cicada nymph emerges after exactly seventeen years underground. Is it running an internal clock, or counting something outside itself?
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Published by: Wiley journalsPublished in a Wiley journal.
doi.org/10.1046/j.1461-0248.2000.00164.x
This reference was resolved automatically against Crossref on 2026-08-11.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-08-11.