Bioacoustics of Ruspolia

With 41 valid, often poorly diagnosed and morphologically similar and highly polymorphic species, and 36 junior synonyms, the genus Ruspolia is in desperate need of a comprehensive generic revision, one that combines morphological, molecular, and bioacoustic data. Compounding the problem is the presence of a number of new African species awaiting description (R. Toms, pers. comm., and this study) as well as the possibility that the New World genus Neoconocephalus Karny , a taxon that exhibits a similar morphological uniformity and an even greater number of species, is a junior synonym of Ruspolia . The most recent review of the African members of the genus ( Bailey 1975 ) has clarified the status of many species but included only rudimentary acoustic data. Subsequent treatments ( Bailey 1976 ; Bailey & McCrae 1978 ) presented songs of several Ruspolia species from Uganda but also pointed out the existence of numerous (‘limitless’) cryptic species in the genus. For this reason, this review of Mozambican katydids does not attempt to formally describe species that do not fit within the diagnoses of the known species but rather presents their morphological and acoustic characteristics, with the hope that their identity will be fully elucidated in a future revision of the genus. At least 6 acoustically distinct but morphologically similar species of Ruspolia occur in Gorongosa and Central Mozambique . They all prefer open, grassy habitats at low elevations, with only R. ampla occasionally found at elevations above 800 m . They are active primarily during the wetter months of the year and, unlike other genera of Mozambican Copiphorini , adults appear to be absent at the peak of the dry season between July and November. They feed mostly on grasses, both leaves and the generative parts. R. differens is a known pest of rice and sorghum in Mozambique and elsewhere in Africa ( Bailey & McCrae 1978 ). Most species are nocturnal although R. ampla often sings during the day.

( Figs. 11E, F , 47 D–F) Diagnostic remarks. A medium-sized Ruspolia , with wings that barely exceed the tips of the hind knees; the apices of the tegmina are broadly rounded ( Fig. 11F ). The morphology of the stridulatory apparatus resembles that of R. differens but the dorsal aspect of the stridulatory file is longer and not thickened in the middle, the file has 132 teeth ( Fig. 11E ). Bioacoustics. The song of this species is a soft, uninterrupted trill with the syllable rate of 50/sec (at 26°C); mean syllable duration 0.012 s (SD=0.00101, n=25), with the frequency peak at 12.3–12.9 kHz ( Figs. 47 D–F). The call is only detectable by the human ear from a distance of a few meters. Measurements ( 3 males , 3 females ). — body w/wings: male 33–34 (33.3.6), female 30–40 (33.75.5); body w/o wings: male 50–55 (53.32.9), female 54–68 (59.37.6); pronotum: male 7–8.9 (81), female 8–9 (8.3.6); tegmen: male 39–47 (43.34), female 46–53 (48.73.8); hind femur: male 22–24 (22.71.2), female 23–25 (241.4); ovipositor: 15.5–27 (22.56.1) mm.

( Figs. 11G, H , 47 G–I) Diagnostic remarks. A medium-sized, robust Ruspolia , with wings clearly exceeding the tips of the hind knees ( Fig. 11H ). The stridulatory file is short, distinctly thickened in the middle, with 88 teeth; the teeth in the proximal (closer to the wing joint) end of the file distinctly larger and more widely spaced than at the distal end. The mirror is nearly perfectly circular ( Fig. 11G ). Bioacoustics. In Gorongosa this species starts singing well before sunset and continues into the night. The call is a typical for Ruspolia uninterrupted trill with the syllable rate of 112/sec (at 26°C); mean syllable duration 0.012 s (SD=0.00375, n=20), with the frequency peak at 10.5–11.7 kHz ( Figs. 47 G–I). The call is loud and readily audible to the human ear. Measurements ( 2 males ). body w/wings: male 40.7–44.3 (42.52.5); body w/o wings: male 24.9–26.9 (25.91.4); pronotum: male 7.7–8.7 (8.2.7); tegmen: male 31.9–34.9 (33.42.1); hind femur: male 18–19.3 (18.7.9) mm.