Orthoptera of North Carolina
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Anaxipha vernalis Walker & Funk, 2014 - Spring Trig


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Taxonomy
Family: Gryllidae Subfamily: Trigonidiinae Tribe: TrigonidiiniSynonym: Anaxipha n. sp. G
Comments: One of thirteen species in this genus that occur in North America north of Mexico (SINA, 2017); nine have been recorded in North Carolina. Vernalis belongs to the Delicatula Species Group, of which declicatula is the only other member.
Species Status: Treated as delicatula by Fulton (1951, 1956) based on genitalic features. Recognized as a separate species by Walker and Funk (2014).
Identification
Field Guide Descriptions: Online Photographs: SINA, Google ImagesTechnical Description, Adults/Nymphs: Walker and Funk (2014)SINA 632a.htm                                                                                  
Comments: A very small, brown Trig. Unlike most members of the Exigua Group, it lacks a stripe on the lateral face of the femur (Walker and Funk, 2014). Structural features -- particularly the number of pegs on the stridulatory file -- must be examined to identify this species. This species is very similar in appearance and in genitalia to delicatula but they can be easily distinguished by their songs.
Total Length [body plus wings; excludes ovipositor]: 6.2-6.8 mm, males; 4.8-6.7 mm, females (Walker and Funk, 2014)
Structural Features: Stridulatory file with about 106 teeth (range 102-112). Ovipositor longer relative to hind femur, HF/O <3.1 (see Walker and Funk, 2014 for additional structural characteristics). Walker and Funk reported that no long-winged forms have been observed.
Singing Behavior: Songs consist of long continuous trills, with the number of pulses per sec greater than 40 at 77 F (= 25 C) and the dominant frequency about 5.5. Anaxipha exigua has a similar call but has a dominant frequency at 77 F of 7.2; exigua also calls much later in the season than vernalis, although there is a period of overlap in late July. Gryllus rubens, which calls during the same time period, has a lower pitch trill but a similar pulse rate; use of spectrograms is recommeded to distinguish these two species.
Recording playback at normal speed.

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Nymphal Stages and Development: Apparently undescribed but unlikely to be distinguishable
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)

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Habitats and Life History
Habitats: Fulton (1956) describes the habitat as primarily fresh-water marshes and stream borders, especially with thick herbaceous growth, including both Lizardtail and tall wetland graminoids. We also have records from floodplain forests more generally and from seepage slopes in the Sandhills.
Diet: Apparently unrecorded; possibly omnivorous
Observation Methods: Singing males are most easily detected both day and night. They may also be captured using sweep netting, although Walker and Funk (2014) state that this species is particularly difficult to capture.
Abundance/Frequency: Can be locally abundant; one chorus heard in Chapel Hill extended well over a half mile along a creek, with no gaps in singing males
Adult Phenology: Fulton (1956) gives the dates for adult vernalis (= delicatula) in the Piedmont of North Carolina as May 22 to July 21
See also Habitat Account for General Sedge, Grass, and Rush Mires
Status in North Carolina
Natural Heritage Program Status:
Natural Heritage Program Ranks: [GNR] [S4?]
State Protection: Has no legal protection, although permits are required to collect it on state parks and other public lands
Comments: We currently have records for this species from just a small number of counties, with most of those being historic. However, it appears to occupy common types of habitats and is likely to be found throughout at least the Piedmont and probably the Coastal Plain.

Image Gallery for Anaxipha vernalis - Spring Trig

Recorded by: Jim Petranka
Swain Co.
Comment: Temp ca. 74; pulse rate ca. 40-45/sec
Recorded by: Ken Kneidel
Mecklenburg Co.
Comment:
Recorded by: Jim Petranka
Madison Co.
Comment: Several adults were singing in -- or immediately adjacent to -- a marshy area dominated by Carex species. Air temp. ca. 75 degrees; 40 pulses per second; individuals made a continuous trill for 20-25 seconds or more; dominant frequency around 5 kZh
Recorded by: Steve Hall and Bo Sullivan
Richmond Co.
Comment: Several males heard singing from the grassy margin of an old beaver impoundment. 60 pulses/sec; >80 F
Recorded by: Steve Hall and Bo Sullivan
Scotland Co.
Comment: Several males heard singing from along a small grassy and shrubby seep; 50 pulses/sec @ ~83 F
Recorded by: Steve Hall
Orange Co.
Comment: 09:52; 78 F; 48 pulses per second. Very few individuals are still calling
Recorded by: Steve Hall, Savannah Hall, Cordell Buckingham
Durham Co.
Comment: 20:00, ~77 F, 43 pulses per sec
Recorded by: Steve Hall
Orange Co.
Comment: 42 pulses per second at 75 F; dominant frequency is about 5.3 kHz. A large chorus has been singing for the past two days at this spot, despite somewhat flooded conditions

MP3 Gallery for Anaxipha vernalis - Spring Trig

1 Recorded by: Jim Petranka
Swain Co.
2021-07-08
Singing male was in vegetation along the banks of the Little Tennessee River; temperature 74 F; pulse rate ca. 40-45/sec.
2 Recorded by: Ken Kneidel
Mecklenburg Co.
2021-06-13
Cattail marsh of roughly 3 acres bordered by extensive lizard tail. Calls were coming from weedy vegetation along the edge, not in the marsh. 42 pulses per second, 5.5 kHz, 79 F time 20:40.
3 Recorded by: Jim Petranka
Madison Co.
2021-05-31
Several adults were singing in -- or immediately adjacent to -- a marshy area dominated by Carex species. Air temp. ca. 75 degrees; 40 pulses per second; individuals made a continuous trill for 20-25 seconds or more; dominant frequency around 5 kZh.