Sinocyrtaspis, Pseudocosmetura fengyangshanensis

Putting S. truncata aside, the song structure is relatively similar throughout the genus and it is a little difficult to divide elements within isolated syllables. In the most simple cases, a tettigoniid syllable is made of heavily damped impulses, which obviously is not the case here; likewise, for crickets, a syllable is made of a long impulse, as is not the case here either. The elements within syllables in Sinocyrtaspis spp. appear to be an admixture of heavily damped and long syllables. Montealegre-Z et al. (2006) ana- lyzed a brachypterous species in Meconematinae from South America, and defined its syllable type as SSTP (short spaced tonal pulses). But the impulses in Sinocyrtaspis are slightly different; a high-amplitude impulse follows a low one, so it is a short spaced compound pulse (SSCP) instead of a tonal impulse. If species with similar songs occurred in the same area, it would be hard to perform acoustic separation (Hemp & Heller, 2017). As for Sinocyrtaspis species, overlapping distribution were not found in the field. Species with similar calling songs but morphological differences suggest allopatric speciation based on genitalic differentiation in Sinocyrtaspis (see Çıplak et al., 2009).

The peak frequencies of Sinocyrtaspis species are >10 kHz, and ultrasonic frequencies account for a large proportion (Fig. 8). The ultrasonic bandwidth of each species is obvi- ously different. For example, S. truncata has an unusually high peak frequency, but the recordings of this species should be re-confirmed; according to the sonogram (Fig. S4), the acous- tic signal contained elements with different frequencies, partly even more strongly frequency modulated, and thus very likely to be produced by a bat or another mammal rather than an insect.

Heller & Hemp (2018) pointed out that large species produce sounds with lower peak frequency compared with small species. The body size of P. fengyangshanensis is smaller than the species in Sinocytraspis, and the peak frequency of the species is distinctly higher and frequency bandwidth narrower than in Sinocyrtaspis (Fig. 8).
In a study on another species with inflated pronotum, Heller (2004) suggested, based on the study of Morris & Mason (1995), that the space between tegmina and inflated pronotum may act as a Helmholtz resonator. Such species have a broarder song spectrum when the inflated pronotum is removed (Jons- son et al., 2017). However, although some species have strongly inflated pronotum, their spectral bandwidth is larger than in other species. Based on that, Kaya et al. (2018) assumed that an inflated pronotum may protect tegmina. The pronotum of the male in Sinocyrtaspis is rather strikingly elevated in metazona. When recording calling songs in the field, the present authors observed that the male pronotum was lifted up, almost perpen- dicular to the body (Fig. S2), and the spectrum bandwidth was wider than in P. fengyangshanensis in which the male prono- tum is not raised in metazona. Based on these observations, it is speculated that the elevated male pronotum at metazona is used to protect tegmina. To decide whether this special pronotum acts as a Helmholtz resonator or not, further research is needed. [1]

References