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Riley's tree cricket

Oecanthus rileyi Baker 1905

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20 s of calling song; male from Cochise Co., Ariz.: Chiricahua Mts.; 24.6°C. (WTL588-11)
spectrogram
 Click on sound bar to hear graphed song.
Sound spectrogram of 2 s of calling at 24.6°C (from WTL588-11). Dominant frequency 2.3 kHz.
Click on spectrogram to expand image of last chirp.
Song at 25°C: Regular, melodius chirps at ca. 1.9 ch/sec. Chirps usually have either 11, 8, or 14 pulses, produced at ca. 52/sec. A chirp's pulses are not quite evenly spaced—chirps generally begin with a group of two pulses closely followed by consecutive groups of three. Thus most chirps have pulses grouped as 2,3,3,3 or 2,3,3 or 2,3,3,3,3. Carrier frequency is 2.7 kHz.
Song data: See Fulton 1925 and Walker 1962.
Identification: Length 15–18 mm. Black mark on first antennal segment round or oval; length of black mark on second antennal segment less than half length of segment; width of dorsal field of male forewings more than 0.4 the length; more than 35 teeth in stridulatory file.
Similar species: Snowy tree cricket—length of dark mark on second antennal segment more than half length of segment; center of mark near center of segment.
Habitat: Vines, shrubbery, low trees and crowns of high trees; chaparral; berry bushes and wild rose.
Season: Late June to November in southern California; August until killing frosts farther north; one generation annually.
Remarks: Riley's tree cricket, like the snowy, can substitute for a thermometer because its chirps are easily countable and their rate correlates well with the temperature at the cricket. A recipe for estimating Fahrenheit temperature from the song of Riley's tree cricket, derived from data collected by B. B. Fulton in Oregon, is to count the chirps in 22 sec and add 37.
More information:
genus Oecanthus, subfamily Oecanthinae.
References: Fulton 1925, 1926b; Walker 1962; Walker & Gurney 1967. Collins 2010-date.
Nomenclature: OSF (Orthoptera Species File Online).
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