Bioacoustics of Horatosphaga serrifera

Distribution and natural history. H. serrifera , originally described from an unknown location in Mozambique ( Schaum 1853 ) and then again, as Pantolepta multivenosa , from Nova Chupanga by Chopard (1935) , is a species widely distributed in sub-Saharan Africa. It has been recorded from the Democratic Republic of the Congo , Angola , Zambia , Kenya , Zimbabwe , Namibia , South Africa , and Mozambique ( Ragge 1960 ). In Mozambique adults of H. serrifera are found only during the wet season, between January and April. They are found on tall herbaceous plants and bushes, occasionally on grass. In Gorongosa remains of males, but not females, of this species are frequently found under roosts of Egyptian whispering bats ( Nycteris thebaica Geoffroy, 1881 ), suggesting that the bats use the male stridulation to locate their prey. Measurements ( 3 males , 3 females ). body w/wings: male 49–51 (501), female 44–48 (46.72.3); body w/o wings: male 22–24 (23.31.2), female 21–34 (29.77.5); pronotum: male 7–8 (7.3.6), female 7–9 (81); tegmen: male 40–41 (40.7.6), female 36–39 (371.7); hind femur: male 37–39 (381), female 34–35 (34.3.6); ovipositor: 13–15 (141) mm.

( Figs. 5I , 32 A–D, 52G–I) Diagnostic remarks. A large, long-legged, and strongly sexually dimorphic katydid. Males have long and wide tegmina with a characteristic venation; they are good fliers ( Fig. 32C ). Females have narrow tegmina that do not reach the hind knees and are incapable of flight ( Fig. 32D ). The tympana on the front tibia are articulate (enclosed in cuticular folds) on both sides, the male cerci are simple, with a small, apical inner spine ( Fig. 32B ), and the ovipositor is long, curved, and with distinct serration at the apical portions of both valvulae ( Fig. 32A ). Bioacoustics. As discussed by Hemp et al. (2010) , the call of Acrometopini is often complex, making it difficult to apply the traditional terminology of syllables and echemes to describe it. For this reason, it is preferable to use the term ‘element’ for a more or less fixed sequence of sound events, without attempting to distinguish the sections of the call are the products of full closing or opening of the stridulatory structures. H. serrifera males call from elevated perches and every few minutes fly to another perch, usually a tall her- baceous plant, and start a new bout of calling. The call, lasting on average 1.6–3.0 seconds, is divided into two sections, each with a different frequency spectrum ( Fig. 52G ). The first section is a uniform train of similar, short syllables produced at the rate of 60–80/sec; mean syllable duration is 0.0094 s (SD=0.001325, n=75); the peak frequency of this section of the call is 4.7–9.9 kHz ( Figs. 52H, I ). The first section, which lasts approximately 0.1– 1.0 s , is immediately followed by a more complex section with multiple elements of various duration; some elements resemble long echemes with similar peak frequency as the first section, while others are short clicks (mean duration 0.011 s ) with the peak frequency of 12.9–14.0 kHz ( Figs. 52H, I ).

As discussed by Hemp et al. (2010), the call of Acrometopini is often complex, making it difficult to apply the traditional terminology of syllables and echemes to describe it. For this reason, it is preferable to use the term ‘element’ for a more or less fixed sequence of sound events, without attempting to distinguish the sections of the call are the products of full closing or opening of the stridulatory structures. H. serrifera males call from elevated perches and every few minutes fly to another perch, usually a tall herbaceous plant, and start a new bout of calling. The call, lasting on average 1.6–3.0 seconds, is divided into two sections, each with a different frequency spectrum (Fig. 52G). The first section is a uniform train of similar, short syllables produced at the rate of 60–80/sec; mean syllable duration is 0.0094 s (SD=0.001325, n=75); the peak fre- quency of this section of the call is 4.7–9.9 kHz (Figs. 52H, I). The first section, which lasts approximately 0.1–1.0 s, is immediately followed by a more complex section with multiple elements of various duration; some elements resemble long echemes with similar peak frequency as the first section, while others are short clicks (mean duration 0.011 s) with the peak frequency of 12.9–14.0 kHz (Figs. 52H, I).