Gryllus bimaculatus De Geer

Weissman, David B. & Gray, David A., 2019, Crickets of the genus Gryllus in the United States (Orthoptera: Gryllidae: Gryllinae), Zootaxa 4705 (1), pp. 1-277 : 32-33

Gryllus bimaculatus De Geer

Two Spotted or Black Field Cricket

Figs 11–13

1773. Gryllus bimaculatus De Geer. Mémoires pour servir à l’histoire des insectes 3:521. Type locality: Africa, West Tropical Africa, Mali, Mourdiah. Type deposited in ANSP.

Recognition characters and song. Apparently the most widely, naturally distributed Gryllus species found from the tip of South Africa north into Europe and east as far as Thailand ( Otte & Cade 1984). This is a medium-large sized, short hind femur, usually pure black, short or long hind winged cricket with a shiny pronotum. Most males have a pale, yellowish area ( Fig. 11a ) at the base of each tegmen where they attach to the pronotum. Adult females may be without or have a slight indication of pale tegminal areas ( Fig. 11b ). Brown males are known (see Fig. 11 a , and Otte and Cade 1984). Song ( Figs. 12 , 13; R12–14 ) with 2–6 pulses/chirp, usually 3–5 chirps/second, pulse rate 21–28 at 25°C, dominant frequency 4633–5816 Hz in pet store specimens.

Discussion. As discussed in Weissman et al. (2012), this is one of two non-native US Gryllus (the other being G. locorojo ) that was being commercially raised in 2012 and shipped to US pet food stores for sale to the general public. Such activities will invariably result in the release, either by accident or on purpose, of this species into the environment, similar to what has probably occurred with Acheta domesticus (Weissman et al. 1980) . The effect of such releases is unknown, as is whether or not these crickets can survive and multiply outside of commercial farms. We discussed ( Weissman et al. 2012) why regulatory oversight by federal and state regulatory agencies has been inadequate and suspect that such surveillance has only gotten worse, since 2012, given continued tightening US federal budgets and malaise from both state and federal regulators. Additionally, we have no idea what the current commercial status is for these two species because they are more aggressive and cannibalistic than the replaced A. domesticus , and tend to bite the lizard they are usually being fed to. Thus, the pet-food industry may be voluntarily replacing G. bimaculatus with the ecologically preferred ( Weissman et al. 2012) Gryllodes sigillatus . We present G. bimaculatus here in case they establish feral populations encountered by an inquiring biologist.

DNA. Multilocus 1999-101, from Zimbabwe, maps closest to Old World G. campestris Linnaeus , and at the base of the Gryllus tree along with several other Gryllus taxa ( Fig. 6 , p. 28 ). This position agrees with that seen in more limited 16S mapping (see Fig. 6 in Weissman et al. 2012).

Figures

FIGURE 6. Phylogenetic arrangement of taxa redrawn from Gray et al. (2019). Taxa in grey text are either not considered here because they are not US Gryllus, or are considered only briefly (Pet Store Group; G. bryanti).

FIGURE 11. Male (a) G. bimaculatus with obvious bilateral, pale-yellowish area at base of tegmina. Female (b) with similar, but smaller areas. Both specimens from commercial pet store.

FIGURE 12. Five second calling song of G. bimaculatus (R12-14) commercial pet store, at 25°C.

FIGURE 13. One second spectrogram of G. bimaculatus, same male as in Fig. 12.

FIGURE 14. Head on view of male G. locorojo showing head stripes.

FIGURE 28. Five second waveforms of calling songs of (A) G. pennsylvanicus and (B) G. firmus. G. pennsylvanicus (R04-110) Whatcom Co., WA (S04-91), at 25°C. G. firmus: (R03-255) Gainesville, FL (S03-85), at 25°C.