Gryllus assimilis (Fabricius)

Gryllus assimilis (Fabricius)

Jamaican Field Cricket

Figs 54, 60–66, Table 1

1775 Acheta assimilis . Systema Entomologiae, p. 280. Type from Jamaica lost, according to Alexander (1957). Neotype male ( Fig. 63 View FIGURE 63 ) selected by Weissman et al. 2009: Jamaica, St. Catherine Parish, Worthy Park, 27-xi-1968. T.J. Walker. Type deposited in CAS, Entomology Type #18172.

‘ Gryllus #1’, in part, of DBW notebooks. 2009 Gryllus assimilis Weissman et al. 2009 .

See Cigliano et al. (2019) for complete list of synonymies. Distribution. Texas and Florida only within the US.

Recognition characters and song. Always macropterous, although rare individuals apterous after shedding hind wings. Medium to large size ( Table 1, p. 18), head frequently narrower than pronotum ( Fig. 64 View FIGURE 64 ), dorsal pronotal surface covered with short, fine hairs usually resulting in dull appearance. Song ( Fig. 65, R13-231, S13-44 View FIGURE 65 View FIGURE 13 ) loud, 6–9 (rarely 10) p/c, PR for first pulse pair ranges from 50 to 111, PR of last pair ranges from 40 to 83 ( Weissman et al. 2009). Chirps/second variable, but distinctive and usually <2.5 at 25°C. In the US, only native in southern Texas but introduced in southern Florida ( Alexander & Walker 1962). Probably continuous generations. Only sympatric Texas species (and then only in Brackettville (S10-63) and Big Bend (S16-12), TX) with a similar, but distinctive song is G. personatus , the latter having a faster chirp rate, a shiny pronotum, different microhabitat requirements, and different head and pronotum color patterns.

Derivation of name. “as” = a copper coin; “similis’ = like, resembling, perhaps with reference to an orange/reddish specimen that reminded Fabricius of the color of a copper coin.

Geographic range. ( Fig. 66 View FIGURE 66 ). Native in southern Texas, introduced in Florida ( Alexander & Walker 1962). Fieldwork in 2013 in southern coastal Texas uncovered a much wider distribution than seen in previous years ( Weissman et al. 2009). Ranges through Mexico and Central America, usually east of the Continental Divide. On many Caribbean Islands ( Otte & Perez-Gelabert 2009, Weissman et al. 2019), and possibly into South America ( Weissman et al. 2009). Widespread sale of this cricket species by US pet-feeder suppliers raises the possibility that feral populations could be established outside its normal US-North American distribution ( Weissman et al. 2012). Barranco (2012) claims feral populations of G. assimilis in Spain but doesn’t supply an oscillogram to confirm identification. We believe those crickets could be G. locorojo ( Weissman et al. 2012) .

Habitat. Almost always associated with people and their watered environs such as lawns, golf courses, school grounds, and in towns. Usually in mowed grassy areas and sometimes in holes.

Life cycle and seasonal occurrence. Diapause unknown for any stage of development. Probably 2 or 3 generations/year with overlap of the continuous generations. Collected early June to mid-September, but obviously present at other times of the year.

Variation. Color: Head, pronotum, body, tegmina, and legs from black to tan ( Fig. 64 View FIGURE 64 ). As we have not seen winter/spring individuals, we may be missing darker colored individuals.

Specimens examined. Texas: Bastrop Co., Smithville, 325’, late September. S.M. Bertram. Brazoria Co., Farm Road 521 5.5 m SE Brazoria , 38’, 13-vii-2013 (S13-61). Brewster Co., Big Bend National Park, Rio Grande Village, 1860’, 28-v-2016, (S16-12). Calhoun Co., Port Lavaca, 18’, 12-vii-2013 (S13-57). Cameron Co., Brownsville, sea level, 3-vi-1991 (S91-38). 3.1 m W Boca Chica State Park on Hwy 4, 10-vi-2007 (S07-26). Rio Hondo, 8m, 10-vii- 2013 (S13-44). Intersection Farm Roads 510 and 2480. 2m, 10-vii-2013 (S13-43). Fayette Co., 2 m S Schulenburg, 440’, 9-ix-2010 (S10-65). Schulenburg, 460’, 9-ix-2010 (S10-66); 14-vii-2013 (S13-66). Hidalgo Co., Benson Rio Grande State Park, sea level, 3-viii-2002 (S02-34); 10-vi-2007 (S07-27). Jim Wells Co., Alice, 171’, 11-vii-2013 (S13-48, 49, 50). Kinney Co., Brackettville, 1160’, 7-ix, 2010 (S10-63). Nueces Co., Corpus Christi, sea level, 11- vi-2011 (S11-36); 12-vii-2013 (S13-53). Refugio Co., Tivoli, 12’, 12-vii-2013 (S13-56). Val Verde Co., Del Rio, 1140’, 7-ix-2012 (S10-64). Victoria Co., Victoria, 20’, 4-viii-2007 (S02-37). Willacy Co., Raymondville, 10-vii- 2013 (S13-47). Farm Road 1420 near intersection FR 498, 15’, 10-vii-2013 (S13-46).

DNA. G3373 (Big Bend, TX [S16-12]) in multilocus species tree (Gray et al. 2019); G. multipulsator is closest DNA relative, at least within our study area. DNA data from a more extensive series is presented in Weissman et al. 2009.

Discussion. In Texas, before 2013, we found this species generally uncommon and dispersed, which contrasts with the situation along the east coast of Mexico where G. assimilis is more common. For unknown reasons, collecting in coastal Texas in 2013 uncovered several dense populations and much wider distributions than in previous years. This cricket is loud and singing males are not easily overlooked. Perhaps because of its adaptation to lowland, cool coastal habitats, G. assimilis males still sing well at 04:00 when most other Gryllus species have long ceased singing.

Bertram & Rook (2011a, b) have studied calling songs and biological aspects in this species from the Austin, Texas area, while Pollack & Kim (2013) and Vedenina & Pollack (2012) studied female phonotaxis and variable courtship song in long-term laboratory cultures. Sturm (2014) and Villarreal et al. (2018) examined aspects of mating strategies. Weissman et al. (2012) documented efforts by US and European cricket farms to utilize another Gryllus species, G. locorojo , misidentified as G. assimilis , to replace virus-infected Acheta domesticus as the preferred pet-feeder cricket.

S.M. Bertram notes (pers. comm. to T.J. Walker, March, 2015) that she and her group have encountered thousands of flying individuals at lights in the fall around Smithville, Bastrop Co., TX, in 2007, 2008 or 2009, and 2014. This situation seems similar to those outbreaks described by Alexander & Walker (1962) in Florida.