Count her chirps in 13 seconds and add 40 — that's the air temperature in Fahrenheit, accurate to ±1°F.
JournalDolbear, A.E. (1897). The American Naturalist1897Share →
Snowy Tree Cricket
Oecanthus fultoni
Count her chirps in 13 seconds, add 40 — that's the temperature in Fahrenheit. To one degree.
Curated and rated by Sheriff Six-Legs and The Wild Pest field team · Six Legs Score™ (70/100, Curious tier) · Published Apr 25, 2026 · Updated Apr 28, 2026 · Released CC BY 4.0
70Six Legs
Six Legs Score™
70 / 100
The snowy tree cricket is a living thermometer. Count her chirps in 13 seconds, add 40, and you have the air temperature in Fahrenheit, accurate to ±1°F. The relationship was formalized in 1897 as Dolbear's Law and remains one of the most charming examples of how biology directly tracks physics.
Size
13-19 mm
Lifespan
Adult 2-3 months
Range
Eastern + central North America
Diet
Plants, soft fruits, occasionally other insects
Found in
Tree branches, shrubs, tall meadow grass
Field guide
Oecanthus fultoni is a small pale-green cricket of North American meadows and woodland edges. The species is famous for one of the most precise biological-physical relationships ever documented: her chirp rate tracks ambient air temperature with extraordinary accuracy. Amos Dolbear formalized the relationship in 1897: count chirps in 13 seconds, add 40, and you get temperature in degrees Fahrenheit, accurate to within ±1°F across the cricket's active temperature range (50-85°F). The mechanism is simple chemistry: the muscle reactions powering wing movement run faster as temperature rises, in direct proportion. Many cricket species follow similar laws but with different constants; snowy tree crickets happen to fit a memorably round formula. Their soft, pulsing 'tre-tre-tre-tre' chirp is a defining sound of late-summer evenings across eastern and central North America. Females select mates partly on chirp quality. Eggs are laid in plant stems and overwinter; nymphs hatch in spring.
5 wild facts on file
The relationship is called Dolbear's Law, formalized in 1897 — one of the oldest published biology-physics relationships.
JournalDolbear (1897)1897Share →
The mechanism: muscle reactions run faster as temperature rises, in direct proportion. Pure chemistry, no nervous-system regulation.
JournalRoyal Society BiologyShare →
Females select mates partly on chirp quality — males with cleaner, more rhythmic songs father more eggs.
JournalBehavioral Ecology journalShare →
The soft 'tre-tre-tre' chirp is a defining sound of late-summer evenings across eastern North America — woven into countless Hollywood film soundtracks.
MuseumSmithsonian National Museum of Natural HistoryShare →
Cultural file
Dolbear's Law is taught in introductory biology courses worldwide as the canonical example of how biological systems directly track physical variables. Hollywood sound editors deliberately use snowy-tree-cricket recordings to convey 'warm summer evening' — the species is one of the most-recorded insects in the soundtrack archives.
Sources
JournalDolbear (1897). The American Naturalist1897MuseumSmithsonian National Museum of Natural History
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