Scale effects and constraints for sound production in katydids (Orthoptera: Tettigoniidae): correlated evolution between morphology and signal parameters

Male katydids (Orthoptera: Tettigoniidae) produce mating calls by rubbing the wings together, using specialized structures in their forewings (stridulatory file, scraper and mirror). A large proportion of species (ca. 66%) reported in the literature produces ultrasonic signals as principal output. Relationships among body size, generator structures and the acoustic parameters carrier frequency (f_c) and pulse duration (p_d), were studied in 58 tropical species that use pure‐tone signals. A comparative analysis, based on the only available katydid phylogeny, shows how changes in sound generator form are related to changes in f_c and p_d. Anatomical changes of the sound generator that might have been selected via f_c and p_d are mirror size, file length and number of file teeth. Selection for structures of the stridulatory apparatus that enhance wing mechanics via file‐teeth and scraper morphology was crucial in the evolution of ultrasonic signals in the family Tettigoniidae.     

Reverse stridulatory wing motion produces highly resonant calls in a neotropical katydid (Orthoptera: Tettigoniidae: Pseudophyllinae)

This paper describes the biomechanics of an unusual form of wing stridulation in katydids, termed here 'reverse stridulation'. Male crickets and katydids produced sound to attract females by rubbing their forewings together. One of the wings bears a vein ventrally modified with teeth (a file), while the other harbours a scraper on its anal edge. The wings open and close in rhythmic cycles, but sound is usually produced during the closing phase as the scraper moves along the file. Scraper-tooth strikes create vibrations that are subsequently amplified by wing cells specialised in sound radiation. The sound produced is either resonant (pure tone) or non-resonant (broadband); these two forms vary across species, but resonant requires complex wing mechanics. Using a sensitive optical diode and high-speed video to examine wing motion, and Laser Doppler Vibrometry (LDV) to study wing resonances, I describe the mechanics of stridulation used by males of the neotropical katydid Ischnomela gracilis (Pseudophyllinae). Males sing with a pure tone at ca.15 kHz and, in contrast to most Ensifera using wing stridulation, produce sound during the opening phase of the wings. The stridulatory file exhibits evident adaptations for such reverse scraper motion. LDV recordings show that the wing cells resonate sharply at ca. 15 kHz. Recordings of wing motion suggest that during the opening phase, the scraper strikes nearly 15,000 teeth/s. Therefore, the song of this species is produced by resonance. The implications of such adaptations (reverse motion, file morphology, and wing resonance) are discussed.     

Distribution of sound pressure around a singing cricket: radiation pattern and asymmetry in the sound field

Male field crickets generate calls to attract distant females through tegminal stridulation: the rubbing together of the overlying right wing which bears a file of cuticular teeth against the underlying left wing which carries a sclerotized scraper. During stridulation, specialized areas of membrane on both wings are set into oscillating vibrations to produce acoustic radiation. The location of females is unknown to the calling males and thus increasing effective signal range in all directions will maximize transmission effectiveness. However, producing an omnidirectional sound field of high sound pressure levels may be problematic due to the mechanical asymmetry found in this sound generation system. Mechanical asymmetry occurs by the right wing coming to partially cover the left wing during the closing stroke phase of stridulation. As such, it is hypothesized that the sound field on the left-wing side of the animal will contain lower sound pressure components than on the right-wing side as a result of this coverage. This hypothesis was tested using a novel method to accurately record a high-resolution, three dimensional mapping of sound pressure levels around restrained Gryllus bimaculatus field crickets singing under pharmacological stimulation. The results indicate that a bilateral asymmetry is present across individuals, with greater amplitude components present in the right-wing side of the animal. Individual variation in sound pressure to either the right- or left-wing side is also observed. However, statistically significant differences in bilateral sound field asymmetry as presented here may not affect signalling in the field.     

Trade‐off between flight capability and reproduction in male Velarifictorus asperses crickets

1. There are numerous data that support the trade‐off between flight capability and reproduction in female wing polymorphic insects, but the relationship between wing form and fitness remains poorly investigated in males. 2. In the present study, the development of flight muscle and gonads, spermatophore size, and multiple copulation ability were investigated in both long‐winged (LW) and short‐winged (SW) males to verify this trade‐off, using a wing dimorphic cricket species Velarifictorus aspersus (Walker). 3. The LW males had better‐developed wing muscles than the SW males on the day of emergence, and both of them developed wing muscles after emergence, but the peak of weight in SW males was achieved 4 days later than that of the LW males. The accessory glands (AG) of the LW males developed significantly slower than that of the SW males. These results suggest that development and maintenance of flight muscles have a cost on the development of reproductive organs in male V. asperses. 4. The SW males produced significantly heavier spermatophores in a single copulation and mated more often than LW males. This indicates the SW males have a higher mating success than the LW males, thereby increasing their chance of siring offspring.     

SOUND PRODUCTION AND SOUND EMISSION IN SEVEN SPECIES OF EUROPEAN TETTIGONIIDS. PART I. THE DIFFERENT PARAMETERS OF THE SONG; THEIR RELATION TO THE MORPHOLOGY OF THE BUSHCRICKET

Abstract

Comparative studies of sound production and sound emission in seven species of European tettigoniids have been carried out. The species chosen were two Tettigoniines (Tettigonia cantans, Tettigonia viridissima), two Ephippigerines (Ephippiger discoidalis, Ephippiger ephippiger), and three Decticines (Decticus albifrons, Decticus verrucivorus, Psorodonotus illyricus). The factors which determined the choice of species were the different morphology (for example body shape and weight, and wing size) of the three subfamilies. The parameters of the different songs (e.g. dominant frequency, intensity) are normally not correlated to any of the investigated morphological characteristics of the animals. In the brachypterous species intraspecific correlations exist between wing size and the dominant low frequency band of the call. This frequency band is also observable at related higher frequencies in the ultrasonic range (20–60 kHz), the observed band width increasing with frequency. Sound emission in all species is to some extent directional. This directionality is related to body size and wing structure. The song structure of the different species does not appear to be related to any observable characteristic of the habitat of die animals. A possible exception may be the song of Psorodonotus illyricus with a particularly low dominant frequency band. The phylogenetic development of the songs seems to be determined by relationships between the different species rather than to any factors contributed by the habitat.     

Relationships between body size and sound‐producing structures in crickets: do large males have large harps?

Abstract. Male crickets produce conspicuous acoustic signals to attract mates and deter potential rivals. These signals are created when a male cricket closes his wings rapidly and a file and scraper mechanism causes several areas of the wing to vibrate. The harp is an area of the wing that is part of the resonating structure. Because the harp acts as part of a mechanical resonator, changes in harp area or mass could influence the frequency of sound produced. Because females exhibit stabilizing selection on the frequency used in male songs, we hypothesized that there would be a negative allometric relationship between body size and harp area. In addition, we examined the degree of asymmetry in the harp, wing, and tibia. We examined this in four different species of cricket: Acheta domesticus, Gryllus bimaculatus, Gryllus rubens , and Teleogryllus oceanicus. For each species, we measured pronotum width as an index of body size, tibia length, and the area of the forewing and harp. There were significant differences among species in their morphological characteristics. We observed consistent directional asymmetry in the harp area but not in the total wing area. When wings did exhibit directional asymmetry, it was in the opposite direction of the directional asymmetry observed in the harp. Within species, larger males typically had larger harps and the relationship between harp area and body size exhibited negative allometry. Wing area exhibited an isometric relationship with body size. Our data provide a potential mechanism linking decreases in song frequency with body size in male crickets, and suggest that sensory constraints might influence the morphology of signaling structures in a similar fashion as genitalia.     

SOUND PRODUCTION AND SOUND EMISSION IN SEVEN SPECIES OF EUROPEAN TETTIGONIIDS. PART II. WING MORPHOLOGY AND THE FREQUENCY CONTENT OF THE SONG

ABSTRACT

Sound production in seven species of bush crickets (Tettigonia cantans, T. virridissima, Decticus verrucivorus, D. albifrons, Psorodonotus illyricus, Ephippiger ephippiger, E. discoidalis) has been investigated. Aspects of wing morphology have been compared and show that areas of the dorsal fields and the mirror are correlated with the dominant frequencies of the songs. Tooth removal from the pars stridens produces gaps in the time structure of single syllables but no change in the song power spectra. The removal of the tegminal lateral field in long- and medium-sized wing species (T.c., T.v., D.a., D.v.) produces an increase in the ultrasonic components of caudally-emitted sound. This suggests an absorbing function for the lateral fields in intact animals. In all species removal of a small portion of the mirror frame or of the mirror membrane attenuates the whole stridulatory signal, but especially the ultrasonic components. The mirror therefore functions as an amplifier, especially for high frequencies. Manipulation of the dorsal fields of long- and medium-winged species, or the distal edges of tegmina of brachypterous species, deletes or shifts the songs' dominant frequency. Thus the different tegminal structures (and especially the dorsal fields) contribute to the time structures and power spectra of the stridulatory songs of these species.     

Acoustic Component and Social Context of the Wing Display of the Walnut Fly Rhagoletis juglandis

Courtship signaling via wing vibration, accompanied by sound production, has been reported in several species of tephritids. In this large family of flies, sound communication as well as complex courtship displays appears to be restricted to species with lekking mating systems (i.e., Mediterranean fruit fly, Anastrepha and Dacus species). In contrast, in tephritid species with resource-defense mating systems, such as species in the genus Rhagoletis, little or no courtship behavior, acoustical or otherwise, has been described. Wing displays in Rhagoletis species have been considered to play a visual role. This study describes a distinctive wing display performed by males of the walnut fly, Rhagoletis juglandis. Laboratory experiments and field observations demonstrate that the male wing display plays a role in courtship. We used sound and vibration detectors to record the signals produced by this wing display. Using a combination of techniques, we were able to record both the very low-frequency vibration and its accompanying airborne infrasound (12–22 Hz) produced by the males.     

中国北部不同地点樟子松人工林径向生长对气候响应的差异

通过树木年代学方法,测定了毛乌素和塞罕坝相同密度樟子松(Pinus sylvestris var.mongolica)全木(Ringwood,RW)、早材(Earlywood,EW)和晚材(Latewood,LW)宽度,计算胸高断面积增量(Basal area increment,BAI),并建立了樟子松年轮宽度年表,分析其对气候响应的差异。结果显示,毛乌素(Mu Us)樟子松轮宽随树龄呈"升-降"的曲线变化,塞罕坝(Saihanba)呈线性下降,两地樟子松BAI变化相似,呈"升-降"的曲线变化,EW占RW的65%—70%,表明EW对RW贡献较大。生长期间,毛乌素樟子松早晚材比例保持平稳,塞罕坝EW/RW值下降,LW/RW值上升,两地干旱事件均使LW/RW值下降,EW/RW值上升。差值年表(Residual chronology,RES)相关性分析显示,毛乌素樟子松径向生长主要与4、7月平均降雨,7月标准化降水蒸散发指数(Standardized precipitation evapotranspiration index,SPEI),3、8月平均温度及上年12月和当年3月最低温度呈正相关关系,与上年11月和当年6月最高温度呈负相关关系。塞罕坝樟子松径向生长主要与7、8月平均降雨、SPEI和最低温度呈正相关关系,与当年3、5月最高温度呈负相关关系。结构方程模型表明,毛乌素年平均温度和年SPEI对樟子松RW产生极显著负效应,年平均降雨对RW产生显著正效应,年平均降雨对EW产生极显著正效应,年最低温度和年平均温度分别对LW产生极显著正/负效应。塞罕坝樟子松径向生长对其年气象因子响应与毛乌素相似,但有部分差别,塞罕坝年平均降雨对LW产生极显著负效应,但对EW未达到显著性水平,且年SPEI对塞罕坝樟子松RW和EW产生的干旱胁迫效应明显小于毛乌素。     

Altitude and life‐history shape the evolution of Heliconius wings

Phenotypic divergence between closely related species has long interested biologists. Taxa that inhabit a range of environments and have diverse natural histories can help understand how selection drives phenotypic divergence. In butterflies, wing color patterns have been extensively studied but diversity in wing shape and size is less well understood. Here, we assess the relative importance of phylogenetic relatedness, natural history, and habitat on shaping wing morphology in a large dataset of over 3500 individuals, representing 13 Heliconius species from across the Neotropics. We find that both larval and adult behavioral ecology correlate with patterns of wing sexual dimorphism and adult size. Species with solitary larvae have larger adult males, in contrast to gregarious Heliconius species, and indeed most Lepidoptera, where females are larger. Species in the pupal‐mating clade are smaller than those in the adult‐mating clade. Interestingly, we find that high‐altitude species tend to have rounder wings and, in one of the two major Heliconius clades, are also bigger than their lowland relatives. Furthermore, within two widespread species, we find that high‐altitude populations also have rounder wings. Thus, we reveal novel adaptive wing morphological divergence among Heliconius species beyond that imposed by natural selection on aposematic wing coloration.     

Diversity of wing patterns and abdomen‐generated substrate sounds in 3 European scorpionfly species

In the genus Panorpa (Insecta: Mecoptera), also known as scorpionflies, premating behavior includes repeated sequences of slow wing movements (waving, fanning, flagging) which are accompanied by rapid abdomen vibrations that generate substantial substrate‐borne sound. It is still unknown whether wing patterns or vibratory signals contain information about species identity, sex and/or the quality of potential mating partners. Besides species‐specific pheromones, these multimodal signals may be of particular importance for the maintenance of reproductive isolation in sympatrically occurring scorpionfly species. Here, we analyzed phyologenetic relationships among, and the pattern of forewings as well as substrate‐borne sound in 3 different sympatric Central‐European scorpionfly species (P. communis, P. germanica, and P. alpina). Divergence time estimates, based on 879 bp of the mitochondrial COI gene, indicate longstanding separate evolutionary histories for the studied Panorpa species. Morphological analysis revealed that wing length as an indicator of body size increased in the following order: P. alpina < P. germanica < P. communis. Individuals can be assigned to the correct species and sex with high accuracy just by evaluation of the number of dark spots and the proportion of wing pigmentation. Despite high variability of interpulse period at an individual level, across species analysis revealed a positive correlation of average interpulse period as well as mean signal amplitude with forewing length. These results suggest wing patterns, but less likely vibratory signals, to contain information about species identity. Furthermore, receivers may be able to estimate the body size of a signaler solely on the basis of substrate‐borne sound.     

Male courtship ultrasound produced by mesothoracic tymbal organs in the yellow peach moth <Emphasis Type="Italic">Conogethes punctiferalis</Emphasis> (Lepidoptera: Crambidae)

Insect sound-producing apparatuses are mostly classified into two types: file–scraper and tymbal. Structures and locations of these organs are conserved in some phylogenetic groups, e.g., crickets, grasshoppers, and cicadas. However, moths have evolved diversified sound-producing organs, such as wing castanets and proboscis, in addition to the file–scraper and tymbal, in each species. Here we demonstrate that the yellow peach moth Conogethes punctiferalis (Guenée) (Lepidoptera: Crambidae) has developed mesothoracic tymbal organs never reported so far in insects. Tymbals are male specific and used for generating ultrasonic clicks in mating. We found eight to nine striae on the smooth surface of the tymbal membrane, suggesting the production of several clicks by a single buckle of the membrane in association with contraction/relaxation of the mesothoracic muscles. Acoustic data from click sequences support the idea that the series is generated by side-to-side asynchrony with an active/passive half cycle by an inward/outward buckle, and thus in click group (pulse) production, males emit 28 clicks with the right and left tymbals. The click-producing mechanism is similar, but not homologous, to those of other clicking species in five moth families. Thus, moths have acquired tymbal organs through independent and convergent evolution.     

Male Body Size and Mating Success and Their Relation to Larval Host Plant History in the Moth Rothschildia lebeau in Costa Rican Dry Forest

The moth Rothschildia lebeau uses three tree species as its primary larval hosts in the tropical dry forest of northwestern Costa Rica. These hosts were shown previously to have different relative effects on caterpillar performance, resulting in an apparent host-related life history trade-off between large adult body size on the one hand but low offspring survival on the other. To further assess the potential ecological and evolutionary importance of this trade-off, an observational field study of the relationship between male body size and mating success was conducted. Across mating trials, larger males had a higher probability of being observed mating. Independent of the effect of size, the amount of wing damage an individual had sustained (a measure of relative age) was negatively correlated with the probability a male was observed mating. Within mating trials, the mated male tended to be larger than the average unmated male, but there was no difference in wing damage. Overall, results of this study were consistent with a positive effect of male body size on mating success, consistent with the idea that larval host plant history and its effects on adult body size matters in terms of adult male fitness. However, all sized males were observed mating over the course of the study, and the size advantage did not appear to be particularly strong.     

SOUND PRODUCTION AND SOUND EMISSION IN SEVEN SPECIES OF EUROPEAN TETTIGONIIDS PART III. DETERMINATION OF THE MECHANISM OF SOUND PRODUCTION USING CEPSTRUM ANALYSIS

ABSTRACT

The mechanism of sound production in tettigoniids is examined by applying the method of ‘cepstrum’ analysis to insect calls. The power cepstrum is defined as the inverse Fourier transform of the logarithmic power spectrum. This analysis shows that the tettigoniid sound signal is a convolution in time of probably two components. The first is caused by the initial impact of teeth of the stridulatory file on the left wing against the plectrum on the right wing (termed the input pulse); the second is caused by the oscillating properties of the tegmina (these being a function of the intrinsic frequencies of dorsal fields and mirror and their damping properties). In the cepstrum each component appears as a varying number of peaks. The tooth impacts cause a very low quefrency peak probably representing the time in which the two tegmina are in contact during each impact and high quefrency peaks representing the impulse repetition rate. The oscillating properties of the tegmina cause two major quefrency peaks which can be clearly related to the size of the dorsal fields and of the mirror respectively, and therefore to their intrinsic frequencies. The high damping factor of the tegmina together with the transient shape of the tegminal input pulse causes a strong time limitation of the impulses and is therefore responsible for the broad frequency bands occurring in the power spectra of the tettigoniid songs. The impulse generation of a synthetic tettigoniid song is discussed.     

Morphological differentiation may mediate mate-choice between incipient species of Anopheles gambiae s.s

The M and S molecular forms of Anopheles gambiae s.s. have been considered incipient species for more than ten years, yet the mechanism underlying assortative mating of these incipient species has remained elusive. The discovery of the importance of harmonic convergence of wing beat frequency in mosquito mating and its relation to wing size have laid the foundation for exploring phenotypic divergence in wing size of wild populations of the two forms. In this study, wings from field collected mosquitoes were measured for wing length and wing width from two parts of the sympatric distribution, which differ with respect to the strength of assortative mating. In Mali, where assortative mating is strong, as evidenced by low rates of hybridization, mean wing lengths and wing widths were significantly larger than those from Guinea-Bissau. In addition, mean wing widths in Mali were significantly different between molecular forms. In Guinea-Bissau, assortative mating appears comparatively reduced and wing lengths and widths did not differ significantly between molecular forms. The data presented in this study support the hypothesis that wing beat frequency may mediate assortative mating in the incipient species of A. gambiae and represent the first documentation of a morphological difference between the M and S molecular forms.     

THE GENETIC BASIS OF THE TRADE-OFF BETWEEN CALLING AND WING MORPH IN MALES OF THE CRICKET GRYLLUS FIRMUS

Wing dimorphisms exist in a wide range of insects. In wing-dimorphic species one morph is winged has functional flight muscles (LW), and is flight-capable, whereas the other has reduced wings (SW) and cannot fly The evolution and maintenance of wing dimorphisms is believed to be due to trade-offs between flight capability and fitness-related traits. Although there are well-established phenotypic trade-offs associated with wing dimorphism in female insects, there only exist two studies that have established a genetic basis to these trade-offs. The present study provides the first evidence for a genetically based trade-off in male insects, specifically in the sand cricket Gryllus firmus. Because they have to expend energy to maintain the flight apparatus (especially flight muscles), LW males are predicted to call less and therefore to attract fewer females. To be of evolutionary significance, call duration wing morph, and wing muscle condition (size and functionality) should all have measurable heritabilities and all be genetically correlated. Differences between morphs in male G. firmus in the likelihood of attracting a female were tested in the laboratory using a T-maze where females chose between a LW male and a SW male. Call duration for each male was recorded on the sixth day of adult life. A significant difference in call duration was found between SW and LW males (SW = 0.86 ± 0.01, LW = 0.64 ± 0.01 h). SW males attracted significantly more females than did LW males (63% vs. to 37%). All the traits involved in the trade-off had significant heritabilities (call = 0 75 ± 0 33; wing morph = 0.22 ± 007; muscle weight = 0.38 ± 0.09) and genetic correlations (call and wing morph = -0.46 ± 0.20 for SW, -0.68 ± 0.16 for LW; LW call and muscle weight = -0.80 ± 0.14). These results provide the first documented evidence that trade-offs between a dimorphic trait and a fitness-related character in males has a genetic basis and hence can be of evolutionary significance.     

Potential Reproductive Advantage of Short-over Long-Winged Adult Males of the Cricket <Emphasis Type="Italic">Velarifictorus ornatus</Emphasis>

A trade-off between flight capability and reproduction is well known in adult females of the wing-dimorphic cricket Velarifictorus ornatus, but it is not clear whether such a trade-off exists in adult males of the species. In the present study, we investigated sexual maturation time, mating frequency, and the fertilization success of spermatophores after sequential mating in long-winged (LW) and short-winged (SW) adult males of V. ornatus to evaluate the potential reproductive advantage of the SW over the LW male morph. We found that the SW males of V. ornatus attained sexual maturity earlier and produced heavier spermatophores during the early stage after adult emergence than their LW counterparts. Additionally, within a 24-h mating period, the SW males showed a higher mating frequency, greater spermatophore weight, and shorter intermating time interval compared with their LW counterparts. Although females copulated with the two male morphs produced eggs of similar size, fertilization success by SW males was significantly higher than by the LW males. These results provide support for a trade-off between dispersal capability and reproduction success in wing-dimorphic males of V. ornatus.     

The mechanics of stridulation of the cricketGryllus campestris

Summary Details in the stridulatory movement ofGryllus campestris were investigated using an improved high resolution miniature angle measurement system. The following results were obtained: During the closing (sound producing) stroke, the speed of the plectrum always has the same value (within measuring accuracy) at a given position. Plectrum speed is directly proportional to tooth spacing, which is known to vary along the file. The only exception to this rule were occasions when closing velocities of precisely 2 times the standard value were found. In between values were never recorded. While temperature has a large effect on the opening speed and duration, the closing speed has a very smallQ ₁₀ (0.07) which is equal to theQ ₁₀ of the resonance frequency of the harp. When the harps are removed, the proportionality between tooth spacing and scraper velocity is lost; the velocity is much increased (up to 3-fold) and the variance of the speed is enhanced 5-fold.These results are discussed with respect to 3 hypothetical models explaining the function of the sound generator system. The model describing the cricket sound generator as a clockwork with an escapement system is capable of accommodating all experimental data without any extra assumptions.     

The complex stridulatory behavior of the cricket Eneoptera guyanensis Chopard (Orthoptera: Grylloidea: Eneopterinae)

Crickets produce stridulated sounds by rubbing their forewings together. The calling song of the cricket species Eneoptera guyanensis Chopard, 1931 alternates two song sections, at low and high dominant frequencies, corresponding to two distinct sections of the stridulatory file. In the present study we address the complex acoustic behavior of E. guyanensis by integrating information on the peculiar morphology of the stridulatory file, the acoustic analysis of its calling song and the forewing movements during sound production. The results show that even if E. guyanensis matches the normal cricket functioning for syllable production, the stridulation involves two different closing movements, corresponding to two types of syllables, allowing the plectrum to hit alternately each differentiated section of the file. Transition syllables combine high and low frequencies and are emitted by a complete forewing closure over the whole file. The double-teeth section of the stridulatory file may be used as a multiplier for the song frequency because of the morphological multiplication due to the double teeth, but also because of an increase of wing velocity when this file section is used. According to available phylogenetic and acoustic data, this complex stridulation may have evolved in a two-step process.     

Stridulation of the clear-wing meadow katydid Xiphelimum amplipennis,adaptive bandwidth

Rubbed wings, analysed calls and a peculiar sound generator structure in males of a conocephaline katydid, Xiphelimum amplipennis, give insight into the making of broadband spectra. High shear forces are indicated by a robust forewing morphology. Intensity is high for frequencies in a 20–60 kHz ultrasonic band. Besides a typical katydid sound-radiating mirror and harp, this insect has a long costal series of semi-transparent specular sound radiators. These wing cells are loaded behind by an enlarged and partitioned subwing air space. Calls repeat steadily with five different time domain sound elements. Distinctive spectra are associated with two of these, giving stepwise frequency modulation that combines to create the exceptionally wide spectral breadth. Broadcast sound levels at 10 cm dorsal, right and left, are near 100 dB. Costal wing-cell sound radiation was explored by loading the costal “speculae” with wax. This produced almost no decrease in lateral sound levels, but did alter spectral content. Apparently, this insect’s costal region both baffles and radiates. The species lives at high densities in cluttered vegetation and sound signal attenuation should code via spectral shape for distance ranging.