Glenn K. Morris

Bat Predation and Its Influence on Calling Behavior in Neotropical Katydids

Insectivorous bats have influenced the development of antipredator behavior in moths, green lacewings, crickets, and mantids; until recently, such adaptations were unknown in katydids. Foliage-gleaning bats in Panama can use the female-attracting, airborne calling songs of nocturnal katydids to locate prey. They also feed heavily on these insects. Katydid species sympatric with these bats exhibit markedly reduced calling song duty cycles. Males supplement shortened songs with complex, species-specific tremulations that generate vibrations that are inaudible to bats but reach conspecific females through a shared plant substrate. Female katydids do not call audibly but are also preyed on in large numbers, perhaps as a result of moving toward calling males.

Calling display and mating behaviour of Copiphora rhinoceros Pictet (Orthoptera: Tettigoniidae)

Abstract Substrate-transmitted signals, known from scattered accounts to occur in several species of acoustic Orthoptera, are brought together and briefly reviewed. Males of a neotropical katydid, Copiphora rhinoceros , were found to alternate stereotyped bouts of body vibration (tremulation) with an 8.7-kHz air-borne song. This calling display is remarkable in combining vegetation-conducted transverse waves with stridulation. A complete acoustic analysis accompanies detailed descriptions of three field matings. Females responded to the males display silently but with similar body shaking. Copulation lasted almost 4 h, and courtship was prolonged by repeated male withdrawals. The males coyness probably reflects a costly nutritional investment in a single mating: his spermatophore includes a huge bilobed spermatophylax, consumed by the female after copulation.

Generation of extreme ultrasonics in rainforest katydids

SUMMARY The calling song of an undescribed Meconematinae katydid (Tettigoniidae) from South America consists of trains of short, separated pure-tone sound pulses at 129 kHz (the highest calling note produced by an Arthropod). Paradoxically, these extremely high-frequency sound waves are produced by a low-velocity movement of the stridulatory forewings. Sound production during a wing stroke is pulsed, but the wings do not pause in their closing, requiring that the scraper, in its travel along the file, must do so to create the pulses. We hypothesize that during scraper pauses, the cuticle behind the scraper is bent by the ongoing relative displacement of the wings, storing deformation energy. When the scraper slips free it unbends while being carried along the file and its deformation energy contributes to a more powerful, higher-rate, one-tooth one-wave sound pulse, lasting no more than a few waves at 129 000 Hz. Some other katydid species make pure-tone ultrasonic pulses. Wing velocities and carriers among these pure-tone species fall into two groups: (1) species with ultrasonic carriers below 40 kHz that have higher calling frequencies correlated with higher wing-closing velocities and higher tooth densities: for these katydids the relationship between average tooth strike rate and song frequency approaches 1:1, as in cricket escapement mechanisms; (2) a group of species with ultrasonic carriers above 40 kHz (that includes the Meconematinae): for these katydids closing wing velocities are dramatically lower and they make short trains of pulses, with intervening periods of silence greater than the duration of the pulses they separate. This signal form may be the signature of scraper-stored elastic energy.

Courtship Communication in Meadow Katydids: Female Preference for Large Male Vibrations

Males of the katydid Conocephalus nigropleurum (Orthoptera: Tettigoniidae) shake their body to produce a substrate-borne vibratory signal in the context of courtship and mate attraction. We measured the physical parameters of this tremulation signal and then tested its effectiveness in eliciting taxis by virgin females. We also investigated the role of these vibrations in the choices made by females of larger males as mates. A search for correlations between male weight and vibratory signal parameters revealed a strong negative relationship to inter-pulse interval (ipi). In two-choice playback experiments females oriented towards tremulation vibration when it was the only vibration stimulus provided. In further playback experiments females also distinguished conspecific tremulation from a control vibration. When offered simultaneous presentations of tremulation signals that differed in ipi, females moved toward the stimulus with the shorter ipi indicative of a larger male. This is the first study to demonstrate that tremulation signalling by male katydids encodes critical information on body size, and that females discriminate among different vibratory signals in favour of those indicating a larger male.

Mating and its effect on acoustic signalling behaviour in a primitive orthopteran, Cyphoderris strepitans (Haglidae): the cost of feeding females

SummaryMales of the primitive orthopteran, Cyphoderris strepitans, provide their mates with two types of nuptial food gift during mating: 1) females feed while coupled on the fleshy metathoracic wings of the male and the resultant flow of haemolymph and 2) the spermatophore transferred by the male includes a gelatinous spermatophylax which the female eats after mating. During the peak breeding interval, virgin males secure significantly more matings than their numbers relative to non-virgin males would predict. We tested the hypothesis that non-virgin males, having lost a substantial portion of available energy through previous investment in females, call significantly less than virgin males. Reduced calling should result in the attraction of fewer females and/or a greater risk of intrusion from competing males and consequently, a lowered mating success. Calling activity of male C. strepitans of varying mating status was monitored with a sound activated relay apparatus for two consecutive nights following their capture. Males were of three experimental groups, virgin, freshly wounded males (mated on the same night of capture), and old-wound males (mated at least one night prior to capture). Our cata showed a significant short-term reduction in signalling activity as a consequence of mating. Whereas there was no difference in the time spent calling by virgins on the first and second nights following capture, freshly wounded and oldwound males called significantly less on the first night than on the second. Furthermore, the proportion of males calling on both nights was significantly greater for the virgin and old-wound groups than for freshly wounded males. When the duration over which males called on the first night was compared with that of the second, virgin males showed no difference whereas old-wound males called for significantly shorter intervals on the first night. These results indicate that the cost of a large nutrient investment in females lowers the energy level in males below the threshold required for a prolonged signalling period. After a refractory interval during which males feed and replenish their energy reserves, calling levels equivalent to those which occur prior to mating are regained. Active female choice may also contribute to the reduced mating success of non-virgins, but this possibility remains untested.

The spiny devil katydids, Panacanthus Walker (Orthoptera: Tettigoniidae): an evolutionary study of acoustic behaviour and morphological traits

Abstract.  A cladistic analysis and systematic revision of the genus Panacanthus accompanies the description of three new species, with calling songs reported for four species. The evolutionary origin of spines is considered as a defensive mechanism in Panacanthus; both morphological and behavioural (i.e. acoustic) traits allow inferences about relationships. Phylogenetic analysis produced one most parsimonious cladogram eighty‐two steps long, with the ensemble consistency index = 0.84. Panacanthus cuspidatus and P. pallicornis (formerly Storniza Walker 1869, Martinezia Bolivar 1881) are properly incorporated in Panacanthus. On morphology, Panacanthus is more related to the Neotropical Copiphora and Lirometopum than to the Old World Lesina. Character analysis reveals that in Panacanthus the ancestral condition of calling song resonance (the production of musical sounds) has given rise to a more nonresonant (transient) stridulation. A correlation between the production of more complex sound waves and spinous protection of the body (especially the pronotum) is noted. Because early workers grouped Panacanthus with other spiny genera, based on pronotal morphology, we present a critique of the evolutionary and ecological implications of the development of defensive spines in this genus. This approach may be applied to other taxa using a similar protective mechanism. We advise against arrangement of the pronotal, cephalic and femoral armature as a homologous characteristic across subfamilies. Several pronotal processes and modifications evolved independently in other genera of Conocephalinae, Hetrodinae, Pseudophyllinae and Phaneropterinae. The pronotal structure of Panacanthus is unique and may be taken as a synapomorphic characteristic of all its species and as an autapomorphic feature of the genus.

Virgin male mating advantage in a primitive acoustic insect (Orthoptera: Haglidae)

Male reproductive behavior in the relict flightless haglid, Cyphoderris strepitans,entails the generation of sound signals and the provision of nuptial gifts to mates. These food gifts take two forms: (1) a gelatinous mass (spermatophylax) augmenting the spermatophore and (2) fleshy metathoracic wings adapted to be eaten. The female consumes a portion of the males underwings during courtship and copulation and the spermatophylax afterward. The incidence of wing-feeding wounds can be used to monitor the mating success of field-caught males. If, when a male mates, he compromises his ability to provide subsequent nutritive gifts, females would benefit by mating with virgin rather than nonvirgin males. To test this, mating success of virgin and nonvirgin males was compared in a field population. Virgins were found to obtain more matings than explained by their numbers relative to nonvirgins in the population. We conclude that, having mated, a male is at a disadvantage, relative to his virgin competitors, in securing further matings.

Mechanical phase shifters for coherent acoustic radiation in the stridulating wings of crickets: the plectrum mechanism

SUMMARY Male crickets produce stridulatory songs using engaged tegmina (forewings): a plectrum on the left sweeps along a tooth row on the right. During stridulation, the plectrum moves across the teeth and vibrations are amplified by the surrounding cells and veins, resonating at the frequency of tooth impacts. The advance of the plectrum on the file is controlled by an escapement mechanism so that passing each single tooth generates one wave of a highly tonal signal. Both tegmina must oscillate in phase to avoid destructive interference. But as each plectrum-tooth contact begins, the right and left tegmina react in opposite oscillatory directions. A mechanical phase shifter is part of the left tegmen and compensates to achieve wing oscillation synchrony. We use a new technique to simulate plectrum-on-file interactions: in combination with laser vibrometry, this technique assessed plectrum mechanics in the cricket Gryllus bimaculatus. Using an excised teneral file, shaped like a partial gear and moved by a motor, and a microscan Doppler laser vibrometer, plectrum and left-tegmen mechanics were explored. The results show that plectrum and harp oscillate with a phase difference of ca. 156 deg., a shift rather than a complete phase inversion (180 deg.). This phase shift occurs at the site of a large wing vein (possibly A3). Plectrum and harp vibrate with similar fundamental frequency, therefore, plectrum torsion resonant frequency is important for maintaining vibration coherence. The mechanical aspects involved in this partial phase inversion are discussed with respect to the escapement mechanism. The plectrum mechanics and its implications in katydid stridulation are also considered.

CALLING COMMUNICATION IN MEADOW KATYDIDS (ORTHOPTERA, TETTIGONIIDAE): FEMALE PREFERENCES FOR SPECIES-SPECIFIC WINGSTROKE RATES

Summary During their search for a mate, female Conocephalus brevipennis (Orthoptera: Tettigoniidae) exhibit different phonotactic preferences. We presented females with calling song stimuli in no-choice playback experiments to determine the physical form of the sound signals they prefer to approach. Females were attracted by sustained noise, a signal lacking any speciesspecific amplitude modulation (AM) but possessing the ultrasonic carrier band typical of Conocephalus spp. This stimulus approximates the collective output of distant aggregations of calling males in which the species-specific AM features of the song are obscured by the grouped singing. When presented with close-range broadcasts, where detailed song features were not obscured (i.e. the call of a single male), female preference was always for conspecific calling song. We also studied female preference for various modifications of the major physical components of the buzz-tick-gap structure of C. brevipennis calling song to uncover parameters

Size and carrier in the bog katydid, Metrioptera sphagnorum (Orthoptera: Ensifera, Tettigoniidae)

Abstract Among crickets and katydids calling carrier frequency is often inversely related to body size. Within species, this relationship is so far found consistently for species employing nonresonant stridulation, but not always among those using resonant stridulation. Metrioptera sphagnorum, is an unusual acoustic species in making two different spectra, one by nonresonant, one by resonant, stridulation. The nonresonant carrier of this insect correlates inversely with body size; the carrier of the elastic-resonant song part does not. Complex-wave pulses made over the distal half of the stridulatory file, give a nonresonant spectrum with a broad audio band, peaked near 19 kHz; sinusoidal pulses, made over the proximal half of the file, give an ultrasonic peak near 35 kHz. The sometime absence of a body-size effect in resonant stridulation may arise from the importance in this mechanism of tooth-contact rates: these provide a way of affecting carrier independent of isometry. Another possible factor in expressing body size acoustically is that nonresonant radiators may show less departure from natural vibration modes. Sound intensity in M. sphagnorum, though affected by temperature, could not be correlated with size.