Paranocarodes chopardi

behaviour · bio.acousti.ca

The stridulation (sound production) mechanism within Pamphagidae is very diverse because of the secondary adaptation of some structures for its function (García et al. 2014). Almost all cases of sound production in this family have been documented from females as part of the mating behavior. Sound production in males has very rarely been observed (López et al. 2008). Our observations in the field, a product of good luck, for the first time document that the males of P. chopardi stridulate. As far as we know, no other record of stridulation within that particular genus exists. The purpose of stridulation and the behavior of the males while producing the sounds is intriguing. No female was in sight. The two individuals were very active, moving along parallel paths, within less than a meter away from each other. An unresolved issue is whether the two males were stridulating as part of aggression behavior towards each other, or because of the disturbance caused by our presence, and not as part of an attempt to attract females for mating. Ünal (2007) reached similar results for the pamphagid genus Glyphotmethis, documenting that members of this genus produce sounds through Krauss’s organ not to attract the different sex but for defense reasons. The sound produced consisted of ‘clicks’ easily audible from several meters away. We observed that they used a rubbing method, involving the movement of the hind “feet” (it is uncertain whether tarsi or femora are involved), up and down on the vertical axis. Paranocarodes species are extremely squamipterous, with only traces of tegmina found, so the emission of sounds by the males was not achieved by means of rubbing the tegmina against parts of the hind leg, but through a different way, involving most probably parts of the hind legs and the sides of abdomen. Ünal (2007), in his research on Glyphotmethis, observed that the sound was produced by rubbing the hind femur on Krauss’s organ. Massa (2012) studied a large number of Pamphagidae genera for their ability to produce sounds. Krauss’s organ is a small plate situated on both sides of the second abdominal tergite in most pamphagids, and is supposed to have a stridulatory function by rubbing hind femurs against it. This method of sound production is considered most primitive. The species of genus Paranocarodes Bolivar, 1916 have only a just visible Krauss’s organ and no specialized hind femur (Massa 2012), thus have probably abandoned this mechanism, and have secondarily adapted a more evolved method of sound production (García et al. 2014). The tympanum, a structure placed also on both sides of the abdominal tergites, although normally used for hearing only, in this case amplifies the emitted sounds. According to Massa (2012), members of Paranocarodes have a wide tympanum. Paranocarodes chopardi however does not seem to fit that rule as it has a very small tympanum (Ünal pers. comm. 2017).

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