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Jamaican field cricket

Gryllus assimilis (Fabricius 1775)

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map neotype male dorsal neotype male lateral male
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female head file characters  
Alien origin and spread of this SINA species.
21 s of calling song, male from Dade County, Fla., 24.5°C. Dominant frequency 3.6 kHz (WTL483-16). Click on sound bar to hear entire recording.
This sound spectrogram is a 2 s excerpt of the 21 s audio file accessible above. The excerpt begins at 3 s. Click on sound bar to hear graphed song.
spectrogram
74 s of calling, from Cameron County, Tex., 25°C. Dominant frequency 3.6 kHz. Recording by D.B. Weissman (S13-44, R13-231); used by permission. Click on sound bar to hear entire recording.
This sound spectrogram is a 4 s excerpt of the 74 s audio file accessible immediately above. The excerpt begins at 28 s. Click on sound bar to hear graphed song.
spectrogram
Sound spectrogram showing first chirp of 4 s sample immediately above. Click on sound bar to hear graphed song.
spectrogram
22 s of mixed courtship, from Dade County, Fla., 24.5°C. Dominant frequency -- kHz. (WTL483-16mc) Click on sound bar to hear entire recording.
This sound spectrogram is a 4 s excerpt of the 22 s audio file accessible immediately above. The excerpt begins at 18 s. Click on sound bar to hear graphed song.
spectrogram
Song: The song of this species is distinctive. Each chirp has six to ten pulses, with the initial ones being briefer and more rapidly(pulse rate 50–111 per second) delivered than the terminal ones (pulse rate 40–83 per second). All pulses come too fast to be easily heard as separate sounds, and the chirp rate is unusually slow—about one chirp per second. G. assimilis is also distinctive morphologically.
Identification: It has short brownish pubescence on the pronotum, the areas around the compound eyes are light yellow-brown, and the lateral arms of the epicranial suture are easily seen. All individuals are long-winged (Walker and Sivinski 1986), rarely apterous. A key to the adult males of native US Gryllus is in Weissman and Gray (2019).
DNA: DNA analysis shows G. multipulsator to be G. assimilis' closest relative. For more information about DNA testing, see Weissman and Gray (2019).
Similar species: Gryllus personatus, sympatric with G. assimilis, has a faster chirp rate, a shiny pronotum, and inhabits deep cracks in clay soils, such as found in badlands.
Range: Native to south Texas and introduced to south Florida.
Habitat: Associated with human environments, on watered lawns, golf courses, gardens and other maintained grounds.
Life cycle: No diapausing stage, which has facilitated continuous rearing for scientific purposes. Probably 2-3 overlapping generations per year.

Season: June to mid-September, present year-round.
Remarks: From 1915 until 1957, the many species of North American Gryllus were generally classified as Gryllus assimilis or Acheta assimilis, because until songs were used to distinguish species, taxonomists could not agree on what groups of Gryllus specimens deserved species status. The real G. assimilis was described from Jamaica and is known in the United States only from southern Florida and Brownsville, Texas.

Until 2009, southern California populations of a related species (Gryllus multipulsator) were considered to be Jamaican field crickets, but their calling songs are distinctive, with more pulses per chirp and a higher dominant frequency. Those counties in California were plotted on the computer-generated map, which was generated in 2004.
Name derivation: Latin: "as"="copper coin"; "similis" = "like, resembling"; probably in reference to G. assimilis' orange-reddish color.
More information:
subfamily Gryllinae, genus Gryllus
References: Bigelow 1958, Alexander & Walker 1962, Weissman, Walker & Gray 2009, Weissman and Gray 2019
Nomenclature: OSF (Orthoptera Species File Online)
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