Bioacoustics of Svistella fuscoterminata

Discussion. The morphology of genera Svistella and Paratrigonidium are very similar. They are both small in body size, stridulatory apparatus well developed in male, tegmen more or less convex in female. Gorochov (1987) proposed that Svistella spp. have following identification features: posterior lateral lobes of epiphallus elongate and narrow on apex, guide rod elongate, attachment plate of the spermatophore consisting of three sclerites (a narrow middle, bearing no protruding structure, and a pair of lateral ones extending to the sides). Tan & Tony (2012) considered Paratrigonidium venustulum as a member of the genus Svistella , but He et al . (2017) considered this species as a member of Paratrigonidium . Our molecular result showed that Paratrigonidium venustulum was closer to P. nitidum than other Svistella spp., which supports He’s opinion. The diagnostic characteristics of the two genera were limited by a small sample, but now these features should be examined again. The genitalia of S . fuscoterminata illustrate a a similarity between the two genera. This is based on posterior lateral lobes of epiphallus short, similar to Paratrigonidium spp. Secondly, the endophallus does not have arms facing towards two sides, which is similar to Paratrigonidium spp. Thirdly, the ectophallus is long and sclerotized, which is similar to Svistella spp. After careful study of the genitalia of P . nitidum and P . venustulum , we found membranous and shorter ectophallus ( Fig. 2 A-D). Thus, we conclude that the molecular results confirm that use of the morphology of the ectophallus is still a useful identification character for the two genera.

Description. Male. Body small. Head little wider than pronotum, frontal rostrum as 1.5 width as 1 st antennal joint, eyes big. 3rd-5th maxillary palpi long with 5th triangular. Tympana on outside only, posterior tibiae with 3 pairs of dorsal spurs. 5 apical spurs with 2 long inner ones and 3 short outer ones. Stridulatory apparatus well developed, extending to apex of abdomen. Posterior lateral lobes of epiphallus short, with teeth on inner side, ectophallus (=guide rod of Gorochov) sclerotized and long, endophallus (=attachment plate of the spermatophore of Gorochov) long without arms towards two sides as in Fig. 2 IJ. Female similar to male, veins of forewing straight with several cross veins, ovipositor curved without denticle on dorsal side. Coloration. Male, body yellow, face with red stripe between bases of antennae, red around the antennal socket. The 2nd and 3rd tarsus black. Areas near oblique and apical field brown in forewing, subapical part of hind femora with a pair of dark spots. ( Fig. 3A ). Female. Forewing brown with veins transparent ( Fig. 3B ). Songs. Calling song. Temperature: 25 O C ( Fig. 4 ) Songs are very regular with 0.571s ± 0.015s of each chirp, the interval between chirps is 1.244s ± 0.082s . There are 23.714±0.700 pulses in every chirp. Main frequency is 6114.33±25.363Hz. Measurements. (in mm) Male: body: 6.5-6.6, tegmen: 4.9-5.1, hind femur:5.5-5.7; female: body: 5.9-6.0, tegmen: 3.9-4.2, hind femur: 5.6-5.7, ovipositor: 2.7-2.9.