Orthoptera of North Carolina
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View Gryllidae Members: NC Records

Allonemobius walkeri Howard & Furth, 1986 - Walker's Ground Cricket


Taxonomy
Family: Gryllidae Subfamily: Nemobiinae Tribe: Pteronemobiini
Comments: One of ten species in this genus, all of which occur in North America north of Mexico (Cigliano et al., 2017). Eight species have been recorded in North Carolina.
Identification
Field Guide Descriptions: Online Photographs: BugGuide, Google ImagesTechnical Description, Adults/Nymphs: Howard and Furth (1986)SINA 529a.htm                                                                                  
Comments: A red-brown to blackish ground cricket (following Alexnder and Thomas's description of allardi). The head is brown with two to three darker stripes, which are usually not contrasting, particularly at the rear of the head, but forming more distinct spots at the top. Differs in coloration and pattern from A. socius, which has pale, contrasting stripes on the back of the head, and from A. tinnulus, which has a more reddish head and pronotum. However, walkeri cannot be safely distinguished from A. fultoni and allardi based on photos and can only be identified based on specimens or by spectrogram (Howard and Furth, 1986).
Total Length [body plus wings; excludes ovipositor]: 9.9-11.7, males; 9.2-11.7, females (Howard and Furth, 1986)
Structural Features: Males have 183-208 stridulatory teeth, which is well above the range of fultoni and averaging lower than allardi, but overlapping in range (Howard and Furth, 1986). Walkeri is significantly larger than fultoni in all measurements, with a table listing these measurements presented by Howard and Furth.
Singing Behavior: The song of Allonemobius walkeri consists of a long, irregularly broken series of downslurred pulses (see SINA), similar in shape to A. tinnulus, allardi, and fultoni. According to Howard and Furth (1986), walkeri sings at a faster rate than allardi, producing 24-25 pulses per second at 23 degrees C compared to 13-16 for allardi (and still fewer for tinnulus); the dominant pitch ranges from 6.7 to 7.7 kHz. While they found no differences between walkeri and fultoni in terms of dominant pitch or rate of singing, the songs of fultoni are more regularly broken into segments separated by fairly fixed intervals of silence (fultoni also appears to differ in terms of habitats).
Recording playback at normal speed.

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Distribution in North Carolina
County Map: Clicking on a county returns the records for the species in that county.
Adult Dates:
 High Mountains (HM) ≥ 4,000 ft.
 Low Mountains (LM) < 4,000 ft.
 Piedmont (Pd)
 Coastal Plain (CP)

Click on graph to enlarge
Habitats and Life History
Habitats: According to Howard and Furth (1986), A. walkeri inhabits dry grassy fields and pastures, nearly always co-occurring with A. allardi, at least where their geographic ranges overlap. Records from North Carolina include an upland field dominated by Andropogon virginicus; a grassy powerline in a floodplain; and an area of old field habitat also located in a floodplain.
Diet: Probably omnivorous
Observation Methods: Most easily detected by its song
Abundance/Frequency: Usually heard as single indivduals
Adult Phenology: Adults emerge in late summer and fall; eggs overwinter (Howard and Furth, 1986)
See also Habitat Account for General Successional and Semi-Natural Grasslands
Status in North Carolina
Natural Heritage Program Status:
Natural Heritage Program Ranks: [GNR] [SU]
State Protection: Has no legal protection, although permits are required to collect it on state parks and other public lands
Comments: Although this species appears to be associated with common types of habitats, it was considered rare by Howard and Furth (1986). Not enough is yet known about its distribution, abundance, and habitat preferences, however, to accurately assess its conservation status.

Image Gallery for Allonemobius walkeri - Walker's Ground Cricket

Recorded by: Steve Hall
Durham Co.
Comment: 30 pulses per second @ 70 F; faster and lower in pitch than other examples
Recorded by: Steve Hall
Orange Co.
Comment: singing from grassy roadside right-of-way; 24 pulses/sec
Recorded by: Stephen Hall
Orange Co.
Comment: Female, found in the same area where males were recorded singing. Stripes are obscure at the back of the head but more visible on the top; head not as red as tinnulus
Recorded by: Steve Hall and Dee Stuckey
Orange Co.
Comment: 19:31, ~80 F; 27 pulses/sec. Singing from deep grass cover
Recorded by: Steve Hall
Orange Co.
Comment: Calling from beneath thick herbaceous vegetation growing on a berm along a creek; canopy of young Boxelders and other levee forest trees above. Temperature at 16:45 was 79 F (= 26 C); the pulse rate is 20 pulses per second, which is slow for walkeri but faster than for allardi
Recorded by: Steve Hall and Dee Stuckey
Orange Co.
Comment: 26 pulses per second @ 7.4 kHz, 71 degrees F (= 21 C); recorded in a powerline where tall old field forbs were growing next to a grassy path
Recorded by: Steve Hall
Orange Co.
Comment: 30 pulses per sec @ 7.9 kHz; 88 degrees F (31 C); recorded at the edge of a field maintained in broom sedges by mowing