Katydid Species Research Articles

Wing resonances in a new dead-leaf-mimic katydid (Tettigoniidae: Pterochrozinae) from the Andean cloud forests

Day-camouflaged leaf-mimic katydids Typophyllum spp. have a remarkable way of evading predators as male and female forewings appear as bite-damaged leaves complete with necrotic spots. As in all other katydids, males produce sound signals to attract females by rubbing their forewings together. The biophysical properties of these special leaf-like forewings remain obscure. Here we study the wing mechanics and resonances of Typophyllum spurioculis, a new species of leaf-mimic katydid with a broad distribution in the Andes from Western Ecuador to the middle Central Cordillera in Colombia. This species performs an unusual laterally directed aposematic display, showing orange spots that simulate eyes at the leg base. At night, males are conspicuous by their loud, audible calling songs, which exhibit two spectral peaks at ca. 7 and 12kHz. Using micro-scanning laser Doppler vibrometry we find the effective sound radiators of the wings (speculae) vibrate with three modes of vibration, two of which include the frequencies observed in the calling song. Remarkably, this resonance is preserved in the parts of the wings mimicking necrotic leaves, which are in theory not specialised for sound production. The eyespot function is discussed.

Endless forms most hidden: katydids that masquerade as moss.

In the cloud forests of the central range of the Colombian Andes, we discovered a species of katydid (Orthoptera: Tettigoniidae) that imitates mosses to an uncanny degree and is exceedingly difficult to detect. The camouflage exhibited by this particular katydid seems quite specific. We discuss the evolutionary consequences of this sort of specialization. Selection to maintain effective disguises can result in reproductive isolation between populations specialized for different microhabitats, which makes it reasonable to speculate that camouflage may increasing diversification rates. Camouflage could also come at the price of elevated extinction risk. This possibility must be considered because although antipredator defenses are often thought of as leading to “escape-and-radiate” dynamics where diversification follows innovation that allows expansion into new niches, recent work has shown unexpected extinction risk associated with some antipredator adaptations. Highly specialized camouflage would seem an ambiguous case because of its obvious benefits, but also potential costs such as inhabiting habitats with low carrying capacities, vulnerability to predators at high densities if predators form search images, or metabolic trade-offs with thermoregulation. Groups such as the Tettigoniidae provide a tantalizing opportunity for their exceptional diversity, wide geographic distribution, and striking array of disguises suggest that many independent evolutionary experiments have already taken place.

ErechthisKatydids (Tettigoniidae: Conocephalinae) in the Caribbean: New Species from the Bahamas and Hispaniola

Two new species of Caribbean conocephaline katydids (Agraeciini) are described for the previously monotypic genus Erechthis: one from the island of Eleuthera in the Bahamas, one from Hispaniola. The first-named species Erechthis gundlachi occurs on both Cuba and Hispaniola. A median projection (prong) of the subgenital plate is taken as a major generic diagnostic trait. This structure's morphology suggests a device for removal of rival sperm. The mate attraction song of males of the Eleutheran species is a steadily repeating series of chirps, each composed of 3 – 5 pulse trains. In the audio the frequency spectrum is broadband from 11 to beyond 20 kHz, with a coherent peak near 7 kHz. Inconsistency in some within-male song features may reflect this species' isolation from congenerics. The Eleutheran species bears a striking turquoise-colored face apparently absent in the other two species. We hypothesize that this coloration is a predatoravoidance adaptation. Possible Caribbean dispersal scenarios are discussed for these species.

Two Mysterious Tiny Katydids from the Ecuadorian Andes (Orthoptera: Tettigoniidae: Hexacentrinae)

Two very small katydids living in upper montane rainforest and elfin forest at 2500–3200 m on the eastern Andean cordillera of south Ecuador are described: Nubimystrix consuelo gen. et sp. nov. and N. amarui sp. nov. They have strongly reduced wings and feature a confusing mixture of morphological characteristics, such as spiny fore tibiae, unconcealed tympana, and tiny auditory spiracles. Apparently these katydids represent a third South American genus of the small subfamily Hexacentrinae. Males of both species produce at night ultrasound calling songs with carrier frequency ranges from about 23 to 31 kHz. While the song of the first species consists of brief calls, males of the other call very continuously, so that especially the presence of the latter can easily be assessed using an ultrasound detector. With an acoustic record at 3210 m, N. amarui is also the highest-occurring katydid species in the investigated area. Some interrelated aspects of biogeography, ecology, and bioacoustics are discussed.

Animal choruses emerge from receiver psychology.

Synchrony and alternation in large animal choruses are often viewed as adaptations by which cooperating males increase their attractiveness to females or evade predators. Alternatively, these seemingly composed productions may simply emerge by default from the receiver psychology of mate choice. This second, emergent property hypothesis has been inferred from findings that females in various acoustic species ignore male calls that follow a neighbor’s by a brief interval, that males often adjust the timing of their call rhythm and reduce the incidence of ineffective, following calls, and from simulations modeling the collective outcome of male adjustments. However, the purported connection between male song timing and female preference has never been tested experimentally, and the emergent property hypothesis has remained speculative. Studying a distinctive katydid species genetically structured as isolated populations, we conducted a comparative phylogenetic analysis of the correlation between male call timing and female preference. We report that across 17 sampled populations male adjustments match the interval over which females prefer leading calls; moreover, this correlation holds after correction for phylogenetic signal. Our study is the first demonstration that male adjustments coevolved with female preferences and thereby confirms the critical link in the emergent property model of chorus evolution.

Effects of acoustic environment on male calling activity and timing in Neotropical forest katydids

Many characteristics of signals can convey information, but the exact timing of the signal often matters as well. The timing of signals is shaped by selective pressures including mate preferences, predation, and competition. In many insect communities, male calling to attract females is persistent and pervasive, and signal timing interactions among individuals are relatively common. In Neotropical forests, many katydid species are represented in the acoustic environment, but calls are usually short (<40 ms) and infrequent (<10 s of sound per individual per night), characteristics that have likely evolved in response to intense predation by insectivorous bats. We test two alternative hypotheses about signal timing in environments where signaling is rare and costly, either that timing is absent due to the unpredictable nature of the signals or that the rarity of signals places a premium on signal timing and attention to the acoustic environment. We tested these hypotheses by broadcasting conspecific calls, heterospecific calls, and silence to eight species of katydids and measuring calling activity and call timing in each playback treatment. All species changed the amount or timing of calling (or both) as a result of the playbacks, but species responded differently to playbacks, with some calling more or less during specific treatments and some showing differences in the timing of calls relative to playbacks. Although short latency signal timing was not observed, this study shows that Neotropical forest katydids are responsive to their acoustic environment despite an exceptionally low rate of signaling. In many species, males produce signals to attract females, and studies show that the timing of these signals relative to other stimuli can play an important role in mate attraction and predator avoidance. Most of these studies have investigated species that are prolific signalers, due to the ease of collecting data. Here, we extend these theories and test them in Neotropical forest katydids, which produce very short and sporadic acoustic signals. We find that these insects do not display the fast competitive interactions seen in more prolific signalers, but still adjust both the timing and amount of calling in response to what they hear. These findings reveal that insects that signal rarely are still attending to the signaling of others and that their behavior can be strongly affected by the signals of other insects, including insects of other species.

Effects of Increasing Temperature on Acoustic Advertisement in the Tettigoniidae

Acoustic communication in insects is vital for reproduction. In the family Tettigoniidae, certain features of acoustic signals are impacted by ambient temperature. The current study investigates the correlation between increased ambient temperature and signaling behavior in four species of katydids in two subfamilies under conditions that may be encountered as environmental temperatures continue to rise due to climate change. This is the first systematic investigation into the potential effects of temperature on song parameters in these four species. Individuals were tested at five different temperatures, ranging from 20 °C to 40 °C at 5°C intervals, and measurements were taken on six acoustic parameters: buzz duration, interbuzz interval (IBI) duration, number of ticks in the IBI, tick rate in the IBI, pulse rate within a buzz, and percent time spent calling. Results indicated a statistically significant effect of temperature on pulse rate, buzz duration, and interbuzz interval duration for all species tested. The percent time calling and buzz duration increased at higher temperatures in the single species in the subfamily Tettigoniinae, in contrast with the three species in the subfamily Conocephalinae which showed decreased percent time calling and reduced buzz duration in increased temperature. These results highlight the potential differences in the behavioral responses among different species to increasing global temperatures. Further research is necessary to assess the potential impact of variable calling parameters on female choice in these and other katydid species.

Acoustic assessment of species richness and assembly rules in ensiferan communities from temperate ecosystems.

Vocalizing animals are known to produce a wide range of species-specific spectral and temporal communication patterns. As a consequence, the acoustic heterogeneity of insect communities is expected to increase with the number of vocalizing species. Using a combination of simulation models and field surveys, we tested the hypotheses that (1) acoustic heterogeneity increases with the number of cricket and katydid species in ensiferan communities and (2) acoustic heterogeneity of naturally assembled ensiferan communities is higher than that of randomly assembled ones. The slope of the acoustic heterogeneity--species richness relationship in naturally assembled communities was positive but did not differ from that of randomly assembled communities, suggesting a rather weak competition for the acoustic space. Comparing the species richness-acoustic heterogeneity relationship of naturally and randomly assembled communities, our study provides a novel approach for understanding species assembly rules in animal groups that rely on acoustic communication.

A new species of spine-headed katydid Mesagraecia Ingrisch, 1998(Conocephalinae: Agraeciini), with key to species.

The taxonomy of poorly known Mesagraecia Ingrisch, 1998 is reviewed. A new species of Mesagraecia spine-headed katydid (Conocephalinae: Agraeciini) is described from Bukit Larut, Perak, Peninsular Malaysia: Mesagraecia larutensis sp. n. A key to species is also presented.

Little walking leaves from southeast Ecuador: biology and taxonomy of Typophyllum species (Orthoptera, Tettigoniidae, Pterochrozinae).

Eight katydid species of the leaf-mimicking specialist genus Typophyllum were found in the southeast of Ecuador in an area comprising part of the eastern Andean cordillera and foothills toward the Cordillera del Cóndor in elevations between 850 and 3000 m. They are described along with the peculiar calling songs and other interesting aspects of their biology. Three of these species are new: T. morrisi sp. nov., T. onkiosternum sp. nov. and T. vignoni sp. nov. A fourth species represented by a single male is possibly new as well. In males and females of a species considered as identical with T. egregium Hebard 1924, which was previously known from a unique female specimen, was found a remarkable variation of coloration, in addition to the striking sexual dimorphism typical for the genus, with the females being twice as large as the small males. The latter is related to the curious mating behaviour, which is documented for this species and T. erosifolium Walker 1870. The two other species found in the region are T. bolivari Vignon 1925 and T. mortuifolium Walker 1870. The calling songs of four species were recorded. In T. erosifolium and T. morrisi sp. nov. the sounds are almost pure sine waves at the lower boundary of ultrasound. In T. egregium and T. onkiosternum sp. nov. the spectrum of the carrier frequency is broader, which might be related to lower and denser vegetation at higher elevation. Based on the intraspecific variety found in T. egregium and T. erosifolium, which includes variation in tegmina shape and venation pattern, are established several syonymies among Typophyllum species from western South America. T. erosifolium is found to be identical with T. peruvianum Pictet 1888 syn. nov. Additionally are considered identical T. inflatum Vignon 1925 and T. gibbosusm Vignon 1925 syn. nov., T. trigonum Vignon 1925 and T. quadriincisum Vignon 1925 syn. nov., and finally T. lacinipenne Enderlein 1917 and T. acutum Vignon 1925 syn. nov. and T. undulatum Caudell 1918 syn. nov. The discussion treats the problematic taxonomy of the little walking leaves, bioacoustics, the pre-copulatory riding behaviour, the sophisticated mimesis, and very briefly the uncertain position within the katydid phylogeny.

Sensory-based niche partitioning in a multiple predator - multiple prey community.

Many predators and parasites eavesdrop on the communication signals of their prey. Eavesdropping is typically studied as dyadic predator-prey species interactions; yet in nature, most predators target multiple prey species and most prey must evade multiple predator species. The impact of predator communities on prey signal evolution is not well understood. Predators could converge in their preferences for conspicuous signal properties, generating competition among predators and natural selection on particular prey signal features. Alternatively, predator species could vary in their preferences for prey signal properties, resulting in sensory-based niche partitioning of prey resources. In the Neotropics, many substrate-gleaning bats use the mate-attraction songs of male katydids to locate them as prey. We studied mechanisms of niche partitioning in four substrate-gleaning bat species and found they are similar in morphology, echolocation signal design and prey-handling ability, but each species preferred different acoustic features of male song in 12 sympatric katydid species. This divergence in predator preference probably contributes to the coexistence of many substrate-gleaning bat species in the Neotropics, and the substantial diversity in the mate-attraction signals of katydids. Our results provide insight into how multiple eavesdropping predator species might influence prey signal evolution through sensory-based niche partitioning.

The secret stridulatory file under the right tegmen in katydids (Orthoptera, Ensifera, Tettigonioidea).

Males of most species of crickets and katydids produce species-specific calling songs to attract conspecific females. The typical stridulatory apparatus of the Ensifera consists of a file-and-scraper system in the basal dorsal region of the forewings (tegmina): the file on the underside of the cubital vein of one tegmen is composed of a series of lamelliform teeth and is run against the sclerotized scraper at the edge of the other tegmen. The region directly distal of the cubital vein is often thin and glassy and serves to amplify and spread the sound. In stridulating crickets the tegmina are quite symmetrical with both the left and the right one containing a file, which is considered the ancestral condition (Béthoux 2012). Most of these crickets adopted a right-over-left wing overlap and use only the right file. The few extant species of the ancient group Hagloidea have bilaterally symmetrical tegmina, both with functional files, and individual males can change the overlap (Morris & Gwynne 1978). Katydids are distinguished by a left-over-right wing overlap, with a stridulatory file on the underside of the left tegmen, and a scraper on the right one, which usually is also equipped with a mirror as resonating structure.

Shrinking wings for ultrasonic pitch production: hyperintense ultra-short-wavelength calls in a new genus of neotropical katydids (Orthoptera: Tettigoniidae).

This article reports the discovery of a new genus and three species of predaceous katydid (Insecta: Orthoptera) from Colombia and Ecuador in which males produce the highest frequency ultrasonic calling songs so far recorded from an arthropod. Male katydids sing by rubbing their wings together to attract distant females. Their song frequencies usually range from audio (5 kHz) to low ultrasonic (30 kHz). However, males of Supersonus spp. call females at 115 kHz, 125 kHz, and 150 kHz. Exceeding the human hearing range (50 Hz–20 kHz) by an order of magnitude, these insects also emit their ultrasound at unusually elevated sound pressure levels (SPL). In all three species these calls exceed 110 dB SPL rms re 20 µPa (at 15 cm). Males of Supersonus spp. have unusually reduced forewings (<0.5 mm2). Only the right wing radiates appreciable sound, the left bears the file and does not show a particular resonance. In contrast to most katydids, males of Supersonus spp. position and move their wings during sound production so that the concave aspect of the right wing, underlain by the insect dorsum, forms a contained cavity with sharp resonance. The observed high SPL at extreme carrier frequencies can be explained by wing anatomy, a resonant cavity with a membrane, and cuticle deformation.

Functional equivalence of grasping cerci and nuptial food gifts in promoting ejaculate transfer in katydids.

The function of nuptial gifts has generated longstanding debate. Nuptial gifts consumed during ejaculate transfer may allow males to transfer more ejaculate than is optimal for females. However, gifts may simultaneously represent male investment in offspring. Evolutionary loss of nuptial gifts can help elucidate pressures driving their evolution. In most katydids (Orthoptera: Tettigoniidae), males transfer a spermatophore comprising two parts: the ejaculate-containing ampulla and the spermatophylax-a gelatinous gift that females eat during ejaculate transfer. Many species, however, have reduced or no spermatophylaces and many have prolonged copulation. Across 44 katydid species, we tested whether spermatophylaces and prolonged copulation following spermatophore transfer are alternative adaptations to protect the ejaculate. We also tested whether prolonged copulation was associated with (i) male cercal adaptations, helping prevent female disengagement, and (ii) female resistance behavior. As predicted, prolonged copulation following (but not before) spermatophore transfer was associated with reduced nuptial gifts, differences in the functional morphology of male cerci, and behavioral resistance by females during copulation. Furthermore, longer copulation following spermatophore transfer was associated with larger ejaculates, across species with reduced nuptial gifts. Our results demonstrate that nuptial gifts and the use of grasping cerci to prolong ejaculate transfer are functionally equivalent.

From microseconds to seconds and minutes-time computation in insect hearing.

The computation of time in the auditory system of insects is of relevance at rather different time scales, covering a large range from microseconds to several minutes. At the one end of this range, only a few microseconds of interaural time differences are available for directional hearing, due to the small distance between the ears, usually considered too small to be processed reliably by simple nervous systems. Synapses of interneurons in the afferent auditory pathway are, however, very sensitive to a time difference of only 1–2 ms provided by the latency shift of afferent activity with changing sound direction. At a much larger time scale of several tens of milliseconds to seconds, time processing is important in the context species recognition, but also for those insects where males produce acoustic signals within choruses, and the temporal relationship between song elements strongly deviates from a random distribution. In these situations, some species exhibit a more or less strict phase relationship of song elements, based on phase response properties of their song oscillator. Here we review evidence on how this may influence mate choice decisions. In the same dimension of some tens of milliseconds we find species of katydids with a duetting communication scheme, where one sex only performs phonotaxis to the other sex if the acoustic response falls within a very short time window after its own call. Such time windows show some features unique to insects, and although its neuronal implementation is unknown so far, the similarity with time processing for target range detection in bat echolocation will be discussed. Finally, the time scale being processed must be extended into the range of many minutes, since some acoustic insects produce singing bouts lasting quite long, and female preferences may be based on total signaling time.

Updated list and community structure of Tettigonioidea and Acridoidea (Insecta: Orthoptera) of the Alta Murgia plateau (Italy)

Alta Murgia calcareous plateau (southeast Italy) is thought to represent one of the most important area for Orthoptera in southern Italy, both due to its biogeographical concern and its unique richness in semi-natural dry grasslands. Since the half of the last century, no recent synthesis has been proposed for the Orthopterofauna of this area and a revision of old observations was still needed. This paper propose a reviewed list of Tettigonioidea and Acridoidea species from the Alta Murgia plateau, also providing information on local community structure and ecology. Based on the revision of previously published lists of species and on data collected during recent field works, a number of 37 species of grasshoppers and katydids is reported. The majority of species found in literature were confirmed, and six species were recorded as new for the area. Data collected during recent field works also enable to provide information about community structure, with particular focus on grassland habitat. This study also gives suggestions for replicable monitoring of Orthoptera assemblages in this area, as it is a valuable information for habitat surveillance purposes and ecosystem conservation strategies.

Population and seasonal variation in response to prey calls by an eavesdropping bat

The fringe-lipped bat, Trachops cirrhosus, is an eavesdropping predator that hunts frogs and katydids by approaching these preys' sexual advertisement calls. In captivity, bats can rapidly learn to associate novel acoustic stimuli with food rewards. It is unknown how this learning ability is related to foraging behavior in the wild where prey and the calls that identify them vary over space and time. In two bat populations that differ in available prey species (Soberania, Panama, and La Selva, Costa Rica), we presented wild-caught bats with frog calls, katydid calls, and control stimuli. Bats in Soberania were significantly more responsive to complex calls and choruses of the tungara frog, Physalaemus pustulosus, than were bats in La Selva. La Selva bats were significantly more responsive to katydid calls (Steirodon sp.) than Soberania bats. We also examined seasonal variation in bat response to prey cues. Bats were captured in Soberania in dry and wet seasons and presented with the calls of a dry season breeding frog (Smilisca sila), a wet season breeding frog (P. pustulosus), and four katydid species. Bats captured in the dry season were significantly more responsive to the calls of S. sila than bats captured in the wet season, but there were no seasonal differences in response to the calls of P. pustulosus or the katydid calls. We demonstrate plasticity in the foraging behavior of this eavesdropping predator but also show that response to prey cues is not predicted solely by prey availability.

Orthopteran fauna of the Hel Peninsula in Poland

Grasshoppers and katydids (Orthoptera) were studied on sand dunes of the Hel Peninsula in northern Poland in 2013. Altogether, 11 species of grasshoppers and katydids were identified, three of them can be regarded as elements of the fauna characteristic for sand dunes. Species diversity and population density was higher in the seaside with sparse vegetation than in the neighboring pine forest. The reported low species richness is comparable to other peninsula covered by sand. Myrmeleotettix maculates was most abundant, particularly by the seaside with low shrub sand Tetrix bipuncata occurred frequently in each habitat, but especially on the forest gaps.

Maintaining acoustic communication at a cocktail party: heterospecific masking noise improves signal detection through frequency separation.

We examined acoustic masking in a chirping katydid species of the Mecopoda elongata complex due to interference with a sympatric Mecopoda species where males produce continuous trills at high amplitudes. Frequency spectra of both calling songs range from 1 to 80 kHz; the chirper species has more energy in a narrow frequency band at 2 kHz and above 40 kHz. Behaviourally, chirper males successfully phase-locked their chirps to playbacks of conspecific chirps under masking conditions at signal-to-noise ratios (SNRs) of -8 dB. After the 2 kHz band in the chirp had been equalised to the level in the masking trill, the breakdown of phase-locked synchrony occurred at a SNR of +7 dB. The remarkable receiver performance is partially mirrored in the selective response of a first-order auditory interneuron (TN1) to conspecific chirps under these masking conditions. However, the selective response is only maintained for a stimulus including the 2 kHz component, although this frequency band has no influence on the unmasked TN1 response. Remarkably, the addition of masking noise at 65 dB sound pressure level (SPL) to threshold response levels of TN1 for pure tones of 2 kHz enhanced the sensitivity of the response by 10 dB. Thus, the spectral dissimilarity between masker and signal at a rather low frequency appears to be of crucial importance for the ability of the chirping species to communicate under strong masking by the trilling species. We discuss the possible properties underlying the cellular/synaptic mechanisms of the 'novelty detector'.

Descripción de tres nuevas especies de tetigónidos de Costa Rica (Orthoptera, Tettigoniidae)

Description of three new species of katydids from Costa Rica (Orthoptera, Tettigoniidae) Three new species of katydids from the Reserva Biológica Alberto Manuel Brenes (Alajuela) in Costa Rica (Central America) are described. The specimens were collected in the course of the Project INVARTRAB developed by the Central University of Costa Rica and the INIA de Madrid (España). The specimens were sampled by direct prospection on plants and light traps. The new species belong to the genera Phlugis, Scopiorinus and Viadana, respectively. Phlugis ramirezi n. sp. has little developed tegmens and wings, male tenth abdominal tergite ending in two spiniform processes, cerci curved with a basal spur, and four teeth in the apex. Scopiorinus estebani n. sp. shows male tenth abdominal tergite with a longer than broad expansion, subgenital plate depressed in the middle, and lateral spiniform processes at the end. Viadana rowelli n. sp. has rhomboidal tegmens and male cerci with an internal branch with serrulated apex inserted in the last third. Main characters are illustrated and compared in related species in each genus.