Specificity of cicada calling songs in the genus Tibicina(Hemiptera: Cicadidae)
J ER OME SUEUR1 and TH IERRY AUB IN 2
1Ecole Pratique des Hautes Etudes, Biologie et Evolution des Insectes, Museum National d’Histoire Naturelle, Paris, France
and 2Neurobiologie de l’Apprentissage, de laMemoire et de la Communication – Centre National de la Recherche Scientifique,
UMR 8620, Universite Paris Sud, Orsay, France
Abstract. Males of Tibicina cicada species produce a sustained and monotonouscalling song by tymbal activity. This acoustic signal constitutes the first step inpair formation, attracting females at long range, and is involved in male–maleinteractions. The specificity of this signal was investigated for the first time forseven species and one subspecies of Tibicina occurring in France. This analysis wasachieved by describing tymbal anatomy, tymbal mechanism and calling songstructure. Male calling songs are emitted following the same general scheme:tymbals are activated alternately and the successive buckling of the sclerotizedribs that they bear produces a regular succession of groups of pulses. The struc-tural and mechanical properties shared by Tibicina species and subspecies lead to aconsiderable uniformity of the signal shape. Nevertheless, a principal componentanalysis applied to eight temporal and three frequency parameters revealed differ-ences between the signals of the species studied. In particular, calling songsdiffered in groups of pulse rate and/or in peak of the second frequency band(carrier frequency). These acoustic differences are probably linked to differences inthe numbers of tymbal ribs and body size. Groups of pulse rate and/or peak of thesecond frequency band could encode specific information. However, Tibicinacalling songs may not act as distinct specific-mate recognition systems and maynot play a leading role in the mating isolation process; rather, they might merelybelong to a complex set of specific spatial, ecological, ethological and morpho-logical characters that ensure syngamy.
Introduction
The initial step in the mating sequence of insects consists of
bringing motile males and females together in the same
place and at the same time (Alexander et al., 1997). During
this phase, both sexes usually exchange chemical, acoustical,
vibratory and/or visual signals. In many cases, one sex
produces a long-range signal encoding specific reproductive
information that is perceived and decoded by the other sex
(Bradbury & Vehrencamp, 1998). In cicadas (Hemiptera,
Cicadidae), the first stage of pair formation is achieved
essentially through sound communication, with males emit-
ting, by tymbal action, a calling song that the female
receives and uses to locate them (Alexander & Moore,
1958). Previous acoustic descriptions of these calling songs
revealed typical time and frequency patterns for each spe-
cies (Sueur, 2001). Playing a leading role in mate attraction,
long-range signals are commonly assumed to be essential in
the species-specific recognition process of cicadas. There-
fore, they can be considered to act as premating isolating
mechanisms (Dobzhansky, 1937; Mayr, 1963) or as distinct
specific-mate recognition systems (SMRSs) according to the
recognition concept of species (Paterson, 1985).
In many groups of cicada species, important acoustical
differences have been found between species that are mor-
phologically similar, such as those of Cicadetta (Popov,
1997, 1998; Puissant & Boulard, 2000) or Cicada (Simoes
et al., 2000). Acoustic similarity between closely related
species seems to be observed rarely. One such exception
could include species belonging to the Palaearctic genus
Tibicina, and some preliminary acoustic analyses have
shown that the calling songs of these species are similar
Correspondence: Jerome Sueur, Ecole Pratique des Hautes Etudes,
Biologie et Evolution des Insectes, Museum National d’Histoire
Naturelle, 45 rue Buffon, F-75005 Paris, France. Tel.:þ33 1 40 79 31 57;
fax:þ33 1 40 79 36 99; e-mail: [email protected]
Systematic Entomology (2003) 28, 481–492
# 2003 The Royal Entomological Society 481
(Fonseca, 1991, 1996; Boulard, 1995). Such similarity
suggests that calling songs of Tibicina are not involved in
species recognition. However, are the Tibicina calling songs
really similar? We have tried to answer this question by
conducting anatomical and acoustical analyses on seven
species and one subspecies of Tibicina present in the south
of France. The tymbal system of each species was examined
first through structural observations and mechanical experi-
ments. Then, the calling songs of the different taxawere analysed
in the time and frequency domains to determine if fine details of
acoustic structure could encode specific information.
Materials and methods
Subjects and location
Seven species and one subspecies of Tibicina were
recorded in France, Switzerland, Spain and Portugal
(Table 1). All the recordings were made in the field during
June and July 1999–2001. Calling songs of T. steveni
(Krynicki, 1837) recorded by Jean-Marc Pillet (Switzerland,
22 June 2000), Andrej Popov (Georgia, 1 July 1976) and
Stephane Puissant (France, 6 July 2002) were added to our
data to increase the number of signals analysed.
Recording procedure
Recordings were made using a Telinga Pro4PiP micro-
phone (Telinga Microphones, Tobo, Sweden) (frequency
response 40–18 000Hz� 1 dB) connected to a Sony
TCD-D8 digital audiotape recorder (sampling frequency
44.1 kHz, frequency response flat within the range
20–20 000Hz). The recordings were carried out between
11.00 and 18.00 hours, a period corresponding to the
maximal activity of cicadas. The ambient temperature
ranged from 25 to 35 �C with a mean of 31 �C. Additional
recordings by J.-M. Pillet, A. Popov and S. Puissant were
made with similar equipment.
Tymbal anatomy and activity
The morphology of tymbals was described for each
species. In particular, the number of short and long ribs
borne on each tymbal was analysed. To determine whether
tymbal muscles contract alternately or synchronously
during sound production, the distress song produced when
males were handled was recorded with both tymbals intact
or with one tymbal destroyed. The tymbal was destroyed by
an anterior–posterior incision made with a microscalpel.
The rate at which one tymbal muscle contracted was then
determined from oscillograms. In another experiment,
tymbal muscles of animals were exposed by removing the
wings and the abdomen at the third abdominal segment.
The intact tymbal was artificially activated by pulling on the
tymbal muscle apodeme with a thin pair of forceps. Record-
ings were made when all ribs were buckled artificially and
the first long rib alone was twitched artificially.
Signal analysis
Signals were digitized from the analog output of the DAT
recorder at a sampling rate of 32 kHz and then analysed in
both temporal and frequency domains using the SYNTANA
analytical package (Aubin, 1994).
Tibicina calling songs showed a common general design:
a succession of groups of pulses arranged in two subgroups.
Two categories of amplitude modulations were distinguish-
able: a slow amplitude modulation distributed within
groups of pulses and a fast amplitude modulation at the
level of each pulse. In the frequency domain, the power
spectrum of all the signals was characterized by three
main peaks (F1, F2, F3). These frequency peaks were a
by-product of the fast amplitude modulation detected in
the pulses. F1 and F3 correspond to the two lateral bands,
and F2 to the carrier frequency, such that 1/(F2�F1) or
1/(F2�F3) correspond to the modulation rate of pulses.
Table 1. Taxa studied and recording sites. Records of T. steveni in
Switzerland and France refer to Sueur et al. (2003).
Site Region Country
T. corsica corsica (Rambur)
Galeria Haute Corse (2A) France
Monticello Haute Corse (2A) France
Occhiatana Haute Corse (2A) France
Barcaggio Haute Corse (2A) France
T. corsica fairmairei Boulard
Site 1 Herault (34) France
Site 2 Herault (34) France
T. garricola Boulard
Domazan Gard (30) France
Serignan-du-Comtat Vaucluse (84) France
Sesimbra Baixo Alentejo Portugal
T. haematodes (Scopoli)
Cairanne Vaucluse (84) France
T. nigronervosa Fieber
Santo-Pietro-di-Tenda Haute Corse (2A) France
Barcaggio Haute Corse (2A) France
T. quadrisignata (Hagen)
Molitg-les-Bains Pyrenees-Orientales (66) France
Sournia Pyrenees-Orientales (66) France
Campoussy Pyrenees-Orientales (66) France
Sainte-Maxime Var (83) France
T. steveni (Krynicki)
Martigny-Croix Valais Swiss
Martigny-Combe Valais Swiss
Fully Valais Swiss
Castelneau-de-Montmirail Tarn (81) France
Cherkodzi – Georgia
T. tomentosa (Olivier)
Site 1 Herault (34) France
Site 2 Herault (34) France
Site 3 Var (83) France
Mertola Distrito de Beja Portugal
Valencia de Alcantara Provencia de Caceres Spain
482 J. Sueur and T.Aubin
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 481–492
In the temporal domain, call duration (CD), silence
intercall duration (ICD), group of pulses duration (GPD),
group of pulses period (GPP), number of group of pulses
per second (NGP), and number of pulses per group (NP)
were measured (Fig. 1). Cicada males can produce wing-
clicking before they emit their calling song (Boulard,
1990). They can also produce important amplitude
variations at the beginning of sound emission and short
interruptions (< 1 s) during sound production. Therefore,
presence or absence of wing-clicking (WC) at the beginning
of the calling song was noted. The number of amplitude-
modulated variations (NAV) at the beginning of the call
and the number of short gaps (NSG) interrupting the
calling songs were also counted.
In the frequency domain, the three main bands (F1, F2,
F3) were analysed on spectra computed with a fast Fourier
transformation (FFT), using a 512 point window size
(Df¼ 62.5Hz) with 50% overlap at a 32-kHz sampling
rate (Fig. 1).
Because of occasional background noise, fine temporal
analysis (GPD, GPP, NGP, NP) and frequency parameters
(F1, F2, F3) were not available for all males recorded.
Because frequency parameters might be correlated to the
size of the sound source (Bennet-Clark & Young, 1994;
Bennet-Clark, 1998), mean of body length (BL) was calcu-
lated for each taxon and then correlated with F1, F2 and F3.
Statistical analysis
A two-factor principal components analysis (PCA) was
computed first using all temporal and frequency
parameters. This allowed us to identify potential correl-
ations between variables and led us to investigate which
temporal or frequency parameters better explain interspecific
variation. These parameters were analysed with an analysis
of variance (ANOVA) using taxon as the independent variable.
Post-hoc HSD Tukey’s tests for samples with unequal sizes
were used to compare taxon means for significant differences
(Spjotvoll & Stoline, 1973). The significance of the correl-
ation between BL and F1, F2 and F3 was tested using
Spearman’s rank test (Scherrer, 1984). All statistical analyses
were performed using STATISTICA v. 5.1 (StatSoft France,
1996).
Results
Tymbal anatomy and activity
The anatomy of the tymbal of Tibicina species was similar
to that already described for T. haematodes by Sueur &
Aubin (2002a) (Fig. 2). The tymbal muscle was inserted in
the dorsal part of the posterior tymbal plate. A series of
sclerotized ribs ran anterior to the tymbal plate. These long
ribs are orientated dorsoventrally, and are narrower and
more highly sclerotized at their centres. Short ribs alternate
with long ribs. The number of long ribs differed between
species (Table 2). The number of long ribs was asymmetric
(�1) between left and right tymbals in 8.62% of males
examined. A dorsal bar connects long ribs 1–4 or 1–5 of
the T. haematodes tymbal, long ribs 1–4 of the T. tomentosa
tymbal, and all long ribs in the remaining taxa.
Distress songs of Tibicina with both tymbals intact
showed a regular succession of groups of pulses. Each
group of pulses was divided into two subgroups. Distress
songs with one tymbal destroyed were made up of only one
of these subgroups (Fig. 3). This indicated that tymbal
muscles contracted alternately and that each muscle
contraction produces a subgroup of pulses. Thus, each
subgroup of pulses was correlated with the activation of
one tymbal. Manual manipulations of one tymbal showed
F2
F1
0
16
8
0
A
B
C
D
Abs
olut
e am
plitu
de (
linea
r sc
ale)
4000 8000Frequency (Hz)
Freq
uenc
y (k
Hz)
Abs
olut
e am
plitu
de
12000 16000
11.4 s
groups of pulses (slow AM) (fast AM)
sub-groups of pulses
single pulse (fast AM)
0.4 s
0.1 s
0.03 s
F3
Fig. 1. Calling song of T. garricola. A, Spectrum (frequency vs.
absolute amplitude), spectrogram and oscillogram (from top to
bottom) of the beginning of the sequence; B, detailed oscillogram
showing groups of pulses; C, detailed oscillogram showing
subgroups of pulses; D, detailed oscillogram showing pulses.
Specificity of cicada calling songs 483
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 481–492
the production of successive impulses during inward move-
ment (IN) and a single faint pulse during outward move-
ment (OUT) (Fig. 4). We can thus infer that the sound
production of Tibicina species studied is produced following
the scheme IN1 – (OUT1)&IN2 – (OUT2), where subscripts
1 and 2 represent the separate tymbals. The activation of
one rib produced one in-pulse and one out-pulse. The suc-
cession of pulses was thus correlated with the successive
buckling of long ribs.
Signal analysis
Measurements of temporal parameters are summarized
in Table 3 and compared in Figs 5–7. Some general fea-
tures can be recognized first: T. haematodes differed from
other taxa by short CD values and T. tomentosa differed
from other taxa by high NGP values and low GPD, GPP
and NP values. The two subspecies T. c. corsica and
T. c. fairmairei had a similar temporal pattern, except
that NP appeared to be slightly higher in T. c. fairmairei
than in T. c. corsica, although the difference is not significant
statistically (HSD Tukey’s test for samples with unequal sizes,
P>0.1). In addition,T. haematodesproduced thehighestNAV
whereasT. tomentosawas the species that interrupted its calling
song sequence by the highest NSG. Finally, T.garricola
and T. steveni (S. Puissant, personal communication) were the
only two taxa that produced wing-clicking before calling
song production.
Measurements of frequency parameters are summarized
in Table 4 and compared in Fig. 8. Three groups of taxa can
be identified easily: (1) taxa producing ‘low’ frequencies, i.e.
T. haematodes and T. steveni; (2) taxa producing ‘middle’
frequencies, i.e.T. garricola,T. quadrisignata andT. tomentosa;
and (3) taxa producing ‘high’ frequencies, i.e. T. c. corsica,
T. c. fairmairei and T. nigronervosa.
Body lengths and frequency peaks of F1, F2 and F3 were
negatively correlated as shown in Fig. 9 (Spearman correl-
ation rank test, P< 0.01). T. tomentosa appeared as an
exception, because it produced relatively low frequencies
compared with its small body length.
Statistical analysis
Principal components analysis (PCA) of calling song vari-
ation among species is shown in Table 5 and Figs 10 and 11.
Factor 1 explained 43.3% of the total variance and factor 2
explained 21.3%. Species and subspecies were well sep-
arated, as were distant populations of T. garricola. Table 5
and Fig. 10 show that measurements CD, ICD, NAV, NSG
and WC did not contribute significantly to either factor. In
addition, F1, F2 and F3 appeared to be highly correlated, as
were GPD and GPP. Therefore, the significant measure-
ments that can be retained to differentiate among Tibicina
calling songs are F2 (or F1 or F3), GP (or GPP), NGP and
NP. In fact, as shown in Fig. 12, Tibicina calling songs of
the different species can be differentiated using only NGP
and F2, in combination.
NGP and F2 differed between taxa (ANOVA, F18,162¼367.3, P¼ 0). The results of comparisons of NGP and F2
between the different taxa (post hoc HSD Tukey’s test for
samples with unequal sizes) are presented in Table 6.
Except T. c. corsica and T. c. fairmairei, taxa showed
pairwise differences for at least one measurement. The
lowest differences for taxa with overlapping geographical
distributions (Sueur & Puissant, 2002) were observed
between: (1) T. nigronervosa and T. c. corsica that
differed for NGP (P< 0.001) but not for F2 (P> 0.5);
Fig. 2. Representation of a tymbal of T. garricola. Abbreviations:
MI, muscle insertion; LR, long rib; SR, short rib; TP, tymbal plate.
Table 2. Mode, minimum and maximum values, and sample size
(n) for the number of tymbal long ribs for each taxon of Tibicina
studied.
Taxon Mode Min.–max. n
T. corsica corsica 10 10–11 17
T. corsica fairmairei 11 10–11 16
T. garricola 10 9–10 17
T. haematodes 7 7–8 19
T. nigronervosa 8 8–9 18
T. quadrisignata 9 8–9 17
T. steveni 9 8–10 8
T. tomentosa 8 7–8 21
484 J. Sueur and T.Aubin
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 481–492
(2) T. garricola and T. c. fairmairei that differed for F2
(P< 0.001) but not for NGP (P> 0.5); (3) T. garricola
and T. quadrisignata that differed for NGP (P< 0.001) but
not for F2 (P> 0.5); (4) T. steveni and T. haematodes that
differed for NGP (P< 0.001) but not for F2 (P> 0.5).
Furthermore, distant populations of T. garricola differed
for NGP (P< 0.001) but not for F2 (P> 0.5). As already
reported by Sueur & Puissant (2003), distant populations
of T. tomentosa differed for NGP (P< 0.001) but not for
F2 (P> 0.1).
Discussion
Tibicina cicada species are probably the most difficult Medi-
terranean species to identify acoustically in the field. In
most cases, their sustained and monotonous calling songs
do not allow a human listener to distinguish among them.
Nevertheless, our acoustic description identifies some fine
differences between the seven species and the one subspecies
found in France and some differences were detected even at
population level.
Calling songs of Tibicina species share the same general
pattern, consisting of a regular succession of groups of
pulses with three main frequency bands. Assuming Tibicina
to be a monophyletic group, this common pattern could be
considered as a synapomorphic ethological character for
the genus and then could constitute a good candidate for
generic identification. By contrast, calling songs of Tibicina
species mainly differ in the number of groups of pulses
produced per second and in the frequency values of the
pulses. Intraspecific differences have also been found
between distant populations of both T. garricola and
T. tomentosa. The differences between T. garricola populations
could not be interpreted as a subspecific differentiation because
intermediate values could exist for populations distributed
betweenFrance andwesternPortugal. Similarly, thedifferences
observed between T. tomentosa populations were not signifi-
cant enough to divide the population into two distinct taxa, as
already discussed (Sueur & Puissant, 2003).
Which factors could then explain simultaneously the
general similarities and the particular differences observed
between species, subspecies or populations? All taxa studied
here show the same general morphology: the lateral tymbal
covers were lacking, the ventral opercula, short in length,
have a similar shape, and the abdomens also show the same
configuration, being half filled with the air sacs (Sueur,
2002). In particular, no obvious anatomical differences
were found in the tymbal structures: they all exhibit the
same alternation of long and short sclerotized ribs. In addi-
tion, our experiments on tymbal activity show that all the
Fig. 3. Tymbal activity: distress song
of T. garricola emitted with (A) both
tymbals intact and (B) with one tymbal
destroyed.
16
Freq
uenc
y (k
Hz)
Abs
olut
e am
plitu
ide
Abs
olut
e am
plitu
ide
8
0
16
Freq
uenc
y (k
Hz)
8
0
0
0
IN
IN
OUT
0.30 s
OUT
0.08 s
r1
r1
r2 r3r4r5r6
Fig. 4. Tymbal activity: manual activation of the tymbal of
T.garricola, with (A) all ribs buckled and (B) first rib alone buckled.
Specificity of cicada calling songs 485
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 481–492
males produce their calling songs following the same
process as already described for species belonging to
Tibicina (Popov, 1975; for T. steveni and not T. intermedia
Fieber; Fonseca, 1991, 1996, for T. garricola and not
T. quadrisignata). All these common morphological and
mechanical features certainly contribute to the similarity
observed for Tibicina calling songs. In addition, the sound
production mechanism seems to be similar to those of
Abricta curvicosta (Germar) (Young, 1972; Young &
Josephson, 1983a) and Magicicada cassini (Fischer) (Reid,
1971; Young & Josephson, 1983b). Lyristes linnei (Smith &
Grossbeck) (Hennig et al., 1994), Cyclochila australasiae
(Donovan) (Young & Bennet-Clark, 1995; Bennet-Clark,
1997) and Cystosoma saundersii Westwood (Simmons &
Young, 1978; Young, 1980; Bennet-Clark & Young, 1998)
also show the same basic tymbal activation and structure,
but sounds produced by successive ribs are fused in one or
two pulses.
By contrast, we found differences between Tibicina
species in the number of tymbal ribs and also in male
body lengths, both of which are correlated with the signal
structure. First, differences in the number of ribs cause
differences in the number of pulses per groups of pulses
and then modify the duration of these groups of pulses.
Fig. 5. Mean (�xx) and SD for group of pulse duration (GPD) and
group of pulses period (GPP).
Fig. 6. Mean (�xx) and SD for number of pulses per group of pulses (NP). Table3.Average(� xx),SD
andsamplesize
forthetemporalparametersofTibicinacallingsignals.Abbreviations:CD,callduration;IC
D,silence
intercallduration;GPD,groupofpulses
duration;GPP,groupofpulses
period;NGP,number
ofgroupofpulses
per
second;NP,number
ofpulses
per
group;WC,presence
orabsence
ofwing-clicking;NAV,number
of
amplitudevariations;NSG,number
ofshort
gaps;F,France;P,Portugal;S,Spain
Species
CD
ICD
GPD
GPP
NGP
NP
NAV
NSG
WC
T.c.corsica
52.8�35.1
(3)
112.9�96.8
(3)
13.8�0.5
(4)
15.8�0.5
(4)
62�
2(4)
11.8�0.5
(4)
00.28�0.4
(4)
0
T.c.fairmairei
81.5�82.3
(12)
63.2�53.1
(12)
13.7�0.6
(13)
15.9�0.3
(13)
62�1.3
(13)
13.2�0.7
(13)
00.26�0.58(14)
0
T.garricola
(F)
42.2�34.7
(11)
76.4�202.6
(11)
13.3�0.5
(13)
14.9�0.6
(13)
67.2�1.3
(13)
10.9�0.8
(13)
00.09�0.30(15)
1
T.garricola
(P)
61.2�73.2
(3)
399.3�509.9
(3)
16.6�0.9
(5)
18.8�0.5
(4)
55.6�1.5
(5)
12.0�
0(5)
00
1
T.garricola
(FþP)
48.8�25.4
(14)
126.7�156.6
(14)
14.2�1.6
(18)
15.9�1.9
(18)
64�5.5
(18)
11.2�0.9
(18)
00.07�0.26(20)
1
T.haem
atodes
14.0�2.3
(19)
12.8�8.7
(19)
8.2�0.4
(11)
10.2�0.4
(11)
98.3�1.6
(11)
8.0�0.6
(11)
3.66�1.38(14)
0.19�0.32(21)
0
T.nigronervosa
72.1�60.1
(7)
28.4�13.1
(7)
7.9�0.4
(8)
8.9�0.4
(8)
108.6�1.1
(8)
9.0�0.5
(8)
0.33�0.71(8)
0.06�0.18(8)
0
T.quadrisignata
93.8�66.8
(10)
280.8�241.9
(8)
12.1�0.7
(16)
13.9�0.6
(16)
74.1�2.16(16)
10.0�1.0
(16)
0.46�0.83(17)
0.24�0.27(17)
0
T.steveni
186�187(7)
–12.3�1.3
(4)
16.8�1.0
(4)
58.5�3.9
(6)
9.8�0.5
(4)
00
1
T.tomentosa
(F)
50.0�28.1
(6)
163.6�87.1
(5)
4.7�6.8
(9)
6.8�0.4
(9)
152.9�6.1
(9)
6.8�0.4
(9)
01.18�1.17(12)
0
T.tomentosa
(SþP)
76.0�27.6
(4)
452.8�154.5
(4)
4.3�0.8
(7)
6.3�0.5
(7)
167.6�10.0
(7)
6.0�1.2
(7)
01.07�1.24(6)
0
T.tomentosa
(FþSþP)
60.3�29.6
(10)
292.1�199.5
(9)
4.5�0.7
(16)
6.6�0.5
(16)
159.3�10.8
(16)
6.4�0.9
(16)
01.15�1.16(18)
0
486 J. Sueur and T.Aubin
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 481–492
Second, small differences in the physiological and
mechanical properties of tymbal muscles, not revealed by
our investigations, could also generate fine differences in
the number of groups of pulses produced per second.
Third, differences in body length could be responsible
for the differences observed in the frequency bands of
the signals emitted by the different species. Such a rela-
tionship between body length and frequency of calling
song has been documented already for several cicada
species (Bennet-Clark & Young, 1994). Tibicina tomentosa
produces relatively low-frequency song compared with its
short body length. Such a failure in the body length/signal
frequency relationship has been reported already for
Magicicada septendecim (L.) and interpreted in terms of
the thickness of the tympana (Bennet-Clark & Young,
1992). Further morphological studies measuring the
thickness of tympana are needed to look for possible
differences between T. tomentosa and the other Tibicina
studied. Hence, fine differences in morphology and
physiology could engender fine differences in the signal
properties. Such factors have been identified already as
potential forces acting on signal structure and evolution
(Endler, 1992; Forrest, 1994).
We have therefore identified some parameters of sexual,
or fertilization, signals that show small amounts of inter-
specific variation. Such acoustic parameters, mainly the
number of groups of pulses per second and the peak of
the second frequency band, could encode species-specific
information, as behavioural components of distinct
SMRSs (Den Hollander, 1995; Lane, 1995; Villet, 1995).
In Cystosoma saundersii, identification of conspecific
males by females at long range is based only on analysis
of carrier frequency (Doolan & Young, 1989). In Cicada
barbara lusitanica, only rough temporal song structure has
been suggested to be important for song discrimination in
long-range communication (Fonseca & Revez, 2002). A
specific recognition process based simultaneously on fine
frequency and time parameters is indeed quite rare in insects
(Hennig & Weber, 1997). In addition, previous playback
studies using T. haematodes have shown that males were
Fig. 7. Mean (�xx) and SD for number of groups of pulses per
second (NGP).
Fig. 8. Mean (�xx) and SD for peak of first frequency band (F1),
second frequency band (F2) and third frequency band (F3).
Table 4. Average (�xx), SD and sample size for the frequency parameters of Tibicina calling signals. Abbreviations: F1, peak of the first
frequency band; F2, peak of the second frequency band; F3, peak of the third frequency band; F, France; P, Portugal; S, Spain.
Taxon F1 F2 F3
T. c. corsica 8645� 71 (3) 9782� 96 (3) 11081� 101 (3)
T. c. fairmairei 8819� 101 (11) 10029� 131 (11) 11177� 115 (11)
T. garricola (F) 7587� 170 (13) 8529� 124 (13) 9551� 216 (13)
T. garricola (P) 7439� 1168 (5) 8731� 219 (5) 9715� 152 (5)
T. garricola (FþP) 7545� 177 (18) 8585� 175 (18) 9596� 210 (18)
T. haematodes 6641� 218 (9) 7516� 247 (9) 8406� 170 (9)
T. nigronervosa 8620� 101 (8) 9806� 189 (8) 11330� 105 (8)
T. quadrisignata 7503� 113 (10) 8614� 188 (10) 9651� 117 (10)
T. steveni 6416� 234 (8) 7221� 148 (8) 8229� 270 (8)
T. tomentosa (F) 7091� 328 (4) 8299� 219 (4) 9407� 379 (4)
T. tomentosa (SþP) 7214� 88 (4) 8416� 81 (4) 9626� 177 (4)
T. tomentosa (F þSþP) 7153� 231 (8) 8357� 165 (8) 9156� 297 (8)
Specificity of cicada calling songs 487
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 481–492
unable to decode such fine time or frequency parameters,
and they reply even to the calling songs of other species of
Tibicina (e.g. T. c. fairmairei, T. garricola, T. quadrisignata
and T. tomentosa). However, they do not reply to the calling
songs produced by species of other genera showing great
acoustic differences (e.g. Cicada orni L., Cicadatra atra
(Olivier)) (Sueur & Aubin, 2002a, b). Furthermore, fine
temporal parameters of such long-range signals probably
are altered during propagation at great distance (>8m)
through numerous natural obstacles (Wiley & Richards,
1978). Females are probably also unable to discriminate at
long range the calling songs of the different species of
Tibicina, and the specific differences observed here could
be considered as epiphenomena of morphological and ana-
tomical contingencies. In this way, Tibicina calling songs
could not be considered as distinct SMRSs, instead merely
as playing a general role in long-range attraction. When
males and females are at close range, other signals, such as
acoustic courtship signals or chemical, visual or vibrational
signals (Claridge et al., 1999), could play a role in the
Tibicina fertilization system and could act as distinct
SMRSs. Besides, as documented already for crickets
(Walker, 1974) and other cicada species (Alexander &
Moore, 1962) with similar calling songs, other parameters
may maintain species isolation. It is particularly true that
geographical and ecological factors reduce temporal and
spatial overlap between Tibicina taxa in France (Sueur &
Puissant, 2002). To conclude, syngamy in the Mediterra-
nean Tibicina species is probably the result of the combined
action of spatial, ecological, morphological and ethological
factors (among which are acoustic signals), rather than of
only one factor.
Fig. 9. Correlation between body length
(BL) and frequency peaks (F1, F2, F3). cor,
T. c. corsica; fai, T. c. fairmairei; gar, T.garri-
cola; hae,T. haematodes; nig,T.nigronervosa;
ste, T. steveni; tom, T. tomentosa. F1¼14 535.2� 286.083*BL; F2¼ 16 886.06�339.347*BL;F3¼ 19049.24� 383.93*BL.
Fig. 10. Scatterplot of the factor loadings
of a principal components analysis (PCA)
of time and frequency measurements.
Variable names are given in Tables 3 and 4.
488 J. Sueur and T.Aubin
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 481–492
Acknowledgements
We are grateful to Michel Boulard and Thierry Bourgoin
for continual support. We are indebted to Jean-Marc Pillet,
Andrej Popov and Stephane Puissant for kindly providing
recordings of T. steveni. We thank Pierre Teocchi, Laetitia
Teocchi, Jacques Coffin, Dominique Cerqueira, Robert
Germain, Stephane Puissant and Nadine Fille for their
help during our visits to the south of France. We are
indebted to Henry C. Bennet-Clark for critical reading of
the manuscript. We are also grateful to Charles S. Henry
and two anonymous referees for comments and improve-
ment of the English. This study was partially conducted in
the ‘Harmas de Jean-Henri Fabre’ (Museum National
d’Histoire Naturelle, France).
Table 5. Factor loadings of the first two principal components from a principal components analysis (PCA) of time and frequency parameter
measurements. Asterisks indicate loadings where the correlation coefficient R > 0.700. For abbreviations see Tables 3 and 4.
Variable Factor 1 Factor 2
Frequency parameters
F1 � 0.786* 0.561
F2 � 0.769* 0.604
F3 � 0.714* 0.663
Temporal parameters
CD � 0.182 0.223
ICD 0.044 0.010
GPD � 0.853* � 0.470
GPP � 0.833* � 0.482
NGP 0.809* 0.502
NP � 0.935* � 0.124
NSG 0.388 0.356
Other parmeters
NAV 0.508 � 0.427
WC � 0.293 � 0.595
Fig. 11. Scatterplot of the first two factors of a principal components analysis (PCA) of time and frequency measurements. Each data point
represents a single individual, coded by species. Variable names are given in Tables 3 and 4. F, France; P, Portugal; S, Spain.
Specificity of cicada calling songs 489
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 481–492
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Accepted 24 April 2003
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# 2003 The Royal Entomological Society, Systematic Entomology, 28, 481–492