Acoustic communication in the Palaearctic red cicada, Tibicina haematodes: chorus organisation, calling-song structure, and signal recognition

Males of the Palaearctic red cicada, Tibicina haematodes, produce calling songs that are attractive to both sexes. For the first time we (i) describe the organisation of the chorus formed by aggregating males, (ii) analysed the physical characteristics of the calling song, and (iii) used playback experiments of natural, modified, and allospecific signals to investigate the signal-recognition process. Males overlap each other’s calling song and try to call first and last during a chorus, leading to what we term domino and last-word effects, respectively. The calling song consists of a two-part sequence made up of a succession of pulses. It is characterized by slow and fast amplitude modulations and three frequency bands. The structure of the signal varied among individuals in both temporal and frequency parameters. Our playback experiments showed that males make a rough analysis of frequency and duration features of the signal. They pay no attention to amplitude modulations. Because males are not capable of precise analysis, they reply to various allospecific calling songs. Females’ analysis of the calling song being difficult to test, the role of this signal in sexual selection still needs to be documented. Résumé : Les mâles de la cigale rouge paléarctique, Tibicina haematodes, émettent des signaux sonores d’appel qui attirent les deux sexes. Pour la première fois, nous décrivons (i) l’organisation des chœurs par les groupes de mâles, (ii) la structure acoustique des signaux d’appel, (iii) le processus de reconnaissance du signal à l’aide d’expériences de diffusion de signaux naturels, modifiés et allospécifiques. Les mâles superposent leurs signaux d’appel et chaque mâle essaie d’être le premier et le dernier à émettre dans les chœurs, donnant lieu à ce que nous avons appelé les effets « domino » et « dernier mot ». Le signal d’appel comporte deux parties, toutes deux constituées d’une succession d’impulsions. Il est caractérisé par des modulations d’amplitude lente et rapide et par trois bandes de fréquences. Les paramètres de fréquence et de durée diffèrent d’un individu à l’autre. Nos expériences de diffusion indiquent que ces paramètres sont analysés par les mâles de façon peu précise et que les modulations d’amplitude ne sont pas prises en compte. Comme ils n’effectuent pas une analyse acoustique détaillée, les mâles répondent à la diffusion de certains signaux allospécifiques. L’analyse du signal d’appel par les femelles reste difficile à tester et le rôle de ce signal dans la sélection sexuelle demeure inconnu. 136 Sueur and Aubin Introduction During pair formation, many animals communicate by means of rhythmic signals. When the calling sex has no other resources but genes to offer to the other sex, callers tend to cluster at a single site (Alexander et al. 1997). In such dense aggregations, calling individuals tend to either alternate or synchronize their advertisement signals. The emergence of synchronization has recently been interpreted as an epiphenomenon created by competitive interactions between males whose signals overlap (Greenfield and Roizen 1993). In many arthropods, signals involved in such collective behaviour are acoustic (Ewing 1989; Bailey 1991). Among acoustic insects, cicadas probably produce the most intense and striking choruses (Alexander and Moore 1958; Young 1981; Williams and Smith 1991; Wolda 1993; Sueur 2001). Emitted only by males, the calling song, termed calling tymbalisation by Boulard (1995), informs conspecific reproductively receptive females of the caller’s position (Alexander and Moore 1958). Sound production is mainly due to the high rate of repeated deformations of a pair of tymbals (Pringle 1953, 1954). In the case of chorusing species, calling males assemble in a specific area where they form chorus centres. They synchronise their songs with greater or less accuracy. The Palaearctic red cicada, Tibicina haematodes (Scopoli, 1763), forms such choruses with partially overlapping songs. This large species (body length about 30 mm) mainly inhabits woodlands, gardens, and vines. During summer days, when ambient temperatures reach 23–25°C, males produce an intense burst of song consisting of pulses without frequency modulation. We observed the collective acoustic behaviour of this species under natural conditions and report these behaviours here for the first time. We describe the time and frequency features of the calling song through an audiospectrographic analysis. We investigated whether there were individual signatures in either the temporal or the freCan. J. Zool. 80: 126–136 (2002) DOI: 10.1139/Z01-212 © 2002 NRC Canada 126 Received 28 May 2001. Accepted 1 November 2001. Published on the NRC Research Press Web site at http://cjz.nrc.ca on 1 February 2002. J. Sueur. Biologie et Evolution des Insectes, École Pratique des Hautes Études, Muséum National d’Histoire Naturelle de Paris, 45 rue Buffon, F-75005 Paris, France. T. Aubin.1 Neurobiologie de l’Apprentissage, de la Mémoire et des Communications–Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8620, Université Paris Sud, F-91405, Orsay, France. 1Corresponding author (e-mail: [email protected]). J:\cjz\cjz80\cjz-01\Z01-212.vp Tuesday, January 29, 2002 9:55:37 AM Color profile: Disabled Composite Default screen