Electron microscope study of haemolymph cells of Decticus verrucivorus (Orthoptera, Tettigoniidae) in larva and imago stages

The haemolymph of larvae and imago stages of Decticus verrucirus was studied with electron and light microscope. PAS-positive and PAS-negative granules were detected in haemocytes. On the electronograms, granulocytes were recognized as the only type of haemocytes. In the cytoplasm of granulocytes, granules of two types were found: those of mitochondrial origin, and originating from the Golgi apparatus, respectively. The discharge of a secret is realized by the merocrine way. Four stages of granulocyte development have been distinguished: 1) granule formation and organelle development, 2) granule formation and accumulation, 3) active secretion, and 4) cell destruction.     

Electron microscope study of haemolymph cells of Tettigonia cantans (Orthoptera, Tettigonidae)

The haemolymph of Tettigonia cantans (Fuess) has been studied at the preimago and imago stages with both electron and light microscopic methods. PAS-negative granules were detected in histochemical reactions. On electronograms, one type of haemocytes was referred to as granulocytes recognized in haemolymph. In the cytoplasm of granulocytes, two types of granules were found: those of mitochondrial origin, and those being derivatives of the Golgi apparatus. Secret discharge is realized by the merocrine way. Four stages of granulocyte development are distinguished: the formation of granules and organelle development; the formation and accumulation of granules, active secretion, and cell destruction.     

Effect of temperature on spontaneous interneuron activity in grasshoppers Tettigonia cantans and Metrioptera roeselii (Orthoptera, Tettigoniidae)

Using electrophysiological methods, effects of temperature on rhythmic impulsation of spontaneously active neurons of thoracic ganglia was studied in grasshoppers Tettigonia cantans and Metrioptera roeselii. Several types of response to temperature changes were observed. Its elevation caused an increase or decrease of the discharge dispersion and a gradual, proportional or abrupt rise of the impulse rate. On decreasing temperature, the impulsation usually returned to its original state, although sometimes at different rate. In neurons whose impulse rate was close to that of pulse repetition rate in male advertisement calls, this dependence was preserved at temperature changes. On the whole, there is reason to believe that changes of temperature in CNS are accompanied not only by a simple change of the neuronal activity level, but also by a complex readjustment in the neuronal network functioning, which allow preserving optimal level of insect metabolic processes and adequate behavior.     

Changes in land use and habitat availability affect the population genetic structure of Metrioptera roeselii (Orthoptera: Tettigoniidae)

The impact of temporal changes in habitat availability and land use on the present genetic diversity of the grassland katydid species Metrioptera roeselii was investigated in an extensively used agricultural landscape (Lahn-Dill-Bergland, Germany) based on six microsatellite loci. By integrating spatial and temporal dimensions, this study contrasts to conventional approaches that usually record landscape changes at discrete points in time. Molecular data suggest little geographical substructuring of the species. Nevertheless, time-dependent effects on genetic diversity in terms of observed heterozygosity and allelic richness within subpopulations were detected by general linear models (GLM), explaining up to 82 and 13%, respectively. The results indicated that allelic richness was significantly reduced with higher rates of land-use change. Contrastingly, the level of heterozygosity even increased with increasing land-use change, if this rate increase was accompanied by a reduction in grassland amount, while with an increase of grassland amount the level of heterozygosity remained similar. Furthermore, depending on the study site, heterozygosity was differently affected by grassland age of sampled patches and of the surrounding. This is presumably induced by contrasting levels of heterozygosity in combination with differing modes of dispersal due to habitat availability and site-specific matrix effects. The loss of genetic diversity due to frequent land-use change might result in a reduced ability to adapt to landscape change, which is even more relevant in intensively used agricultural landscapes and in the course of climate change.     

Dispersal in a metapopulation of the bush cricket, Metrioptera bicolor (Orthoptera: Tettigoniidae)

1. I present a stochastic simulation model that describes individual movements of Metrioptera bicolor Philippi in a heterogeneous landscape, consisting of patches of suitable habitat surrounded by a matrix of unprofitable habitats. Although the model is parameterized with information about daily movement behaviour, it can generate spatially explicit predictions about inter-patch dispersal rates for much longer periods, e.g. one generation.
2. Long-term dispersal experiments were conducted to evaluate model predictions. Patch-specific emigration rates and the total distance moved by individuals could be predicted with satisfactory precision. Because of the stochastic nature of the model, it failed to predict which recipient patches emigrating individuals actually chose in a particular situation.
3. Spatially explicit simulations of the movement model were made for the whole natural distribution area of M. bicolor . The results suggest that emigration rates are negatively correlated with patch size. Local populations occurring on small patches may be more prone to extinction than those on large patches, by losing more emigrants than are compensated for by immigration.     

The influence of environmental factors on dormancy and duration of egg development in Metrioptera roeseli (Orthoptera: Tettigoniidae)

Summary Developing eggs of Metrioptera roeseli HGB. have an obligate embryonic diapause in stage 23 and a facultative initial diapause in stage 4. Initial diapause is lacking when the ovipositing females are kept at long day photoperiod (LD 16/8), but is induced at LD 14/10 and LD 8/16. When natural light conditions are given in the laboratory, the females mostly lay diapausing eggs from the end of August onwards. In eggs without initial diapause, a larger number of embryos reach a stage, in which the embryonic diapause can be broken by chilling, only at favorable temperature (4 weeks at 24°C or 8 at 18°C) and in contact with water before the first winter. Thus, some individuals of a given population of M. roeseli have an annual, others a biennial life cycle. The variability in the duration of egg development is due to a photoperiodically induced, facultative initial diapause and to a possible quiescence caused by insufficient temperature and/or moisture.     

Colour polymorphism in Ephippiger ephippiger (Orthoptera, Tettigoniidae)

Colour in the Ephippiger ephippiger complex varies with the geographical distribution and with rearing density. In the W European subspecies E. e. vitium , wild insects from northern and eastern parts of the range tend to have green tergites with relatively inconspicuous banding, whereas those from S France have conspicuously pale banded dark-green or brown tergites. These forms represent the ends of a continuum and there is no zone of distinction. However, the E Pyrenean subspecies, E. e. cunii , lacks the broad banding of its neighbouring E. e. vitium. The tergites of laboratory cultured insects of these stocks when reared in isolation are distinctly green but when reared together become progressively brown. The darkness of the brown is density dependant, so that at high densities the tergites may become almost black. These colour changes are irreversible. Adult insects also become darker with sexual maturity and after contact on mating. Wild-caught E. e. ephippiger from Italy and Yugoslavia have green tergites without obvious banding. Colour changes have not been found or induced in this subspecies. The significance of the colour change is considered and although firm data are wanting, circumstantial evidence suggests a deliberate shift to an aposematic or pseudoaposematic colour pattern.     

Ultrasonic startle behavior in bushcrickets (Orthoptera; Tettigoniidae)

1. In the present work, we show that in flight, bushcrickets not previously known to respond to ultrasound alter their flight course in response to ultrasonic stimuli. Such stimuli elicit in flying Neoconocephalus ensiger an extension of the front and middle legs along the body and a rapid closure of all 4 wings (Fig. 1). This is a short latency acoustic startle response to ultrasound, consistent with acoustic startle responses of other insects. 2. The percentage of trials on which acoustic startle responses were elicited was maximum (90%) for sound frequencies ranging from 25 to at least 60 kHz. No acoustic startle response was observed at frequencies of 5 or 10 kHz (Fig. 2). The threshold for the response was roughly 76 dB between 25 to 60 kHz (Fig. 2) and the behavioral latency was 45 ms (Fig. 3). Recordings from flight muscles show that they cease discharging during the acoustic startle response (Fig. 4). 3. The characteristics of the acoustic startle response match those of an auditory interneuron called the T-neuron. The frequency sensitivity of this neuron is greatest for sound frequencies ranging from 13 to 60 kHz (Fig. 6). Moreover, we found that the neuron produces many more spikes to ultrasound (30 kHz) of increasing intensities than to a conspecific communication sound, whose dominant frequency is 14 kHz (Fig. 7).     

Structure of the stridulation ofOrchelimum (Orthoptera: Tettigoniidae)

Summary The structure of the stridulation was investigated by re-playing tape-recordings at very slow speed. The findings were corrobrated by sonograms and mingograms.The central part of the song is the ripple, a fast succession of syllables around which isolated syllables (clicks) are distributed according to species and circumstances. The rate of syllables in the ripple is a linear function of temperature.A quantitative expression for the stridulatory activity is the actual number of syllables per time unit, including pauses. By changes in the combination of elements, at leastO. agile is able to increase the output of syllables four to six times.This work was made possible by a grant from the Carlsberg Foundation to whom my most sincere thanks are due. —As I do not have advanced equipment for sound analysis, I am very much indebted to Dr. Bondesen and cand. sci. Poul Hansen, Bioakustisk Laboratorium, Naturhistorisk Museum, Aarhus, Denmark, and Mr. W.B. Broughton and Dr. M. Samways, Animal Acoustic Unit, City of London Polytechnic, London, for analysing part of the material by sonograms and mingograms. The very valuable help of Dr. Th.J. Walker, University of Florida, Gainesville, Florida, in identifying the species is gratefully acknowledged. For friendly discussions and linguistic corrections my best thanks are due to H.T. Evans and F.D.S. Evans.     

On recognition of sound communication signals in bush crickets (Orthoptera,Tettigoniidae)

Two hypotheses have been proposed to explain the mechanisms of calling signal recognition in orthopterans: the filtration and resonance ones. To test these hypotheses, conspecific male calling songs and their models with modified temporal parameters were presented to females of bush crickets in ethological experiments. The models with a double pulse rate evoked positive phonotaxis of females while phase shift significantly complicated the recognition process. These data fit the resonance hypothesis.     

Some aspects of karyotype of Liarina (Orthoptera: Tettigoniidae, Agraeciini) from Vietnam

Karyotypes (chromosome number and shape) of four species of the subtribe Liarina were studied. The chromosome numbers and NF (Fundamental Number) in this group of species range from 2n Male = 33 (34) to 27(30): Liaromorpha buonluoiensis 2n Male = 33 (34), Sialaiana transiens 2n Male = 29 (34), Liara tramlapensis 2n Male = 29 (32), and Anelytra (Perianelytra) propria 2n Male = 27 (30). Cyto-taxonomy analysis indicates an intensive karyotype evolution among species belonging to three different groups of the genera. Differences of karyotypes are connected with Robertsonian fusion and tandem fusion in autosomes. Additionally, C-banding distribution and location of the NORs were studied.     

The function of sound in male spacing behaviour in bush-crickets (Tettigoniidae,Orthoptera)

This paper examines the spatial dynamics of an aggregation of singing male bush-crickets (Tettigoniidae) in respect to the degree of regularity between males. Our results establish that singing males of the genus Mygalopsis are regularly spaced within aggregations and that sound is involved in spacing. Attention is focussed on the male strategy of regular spacing within a widely dispersed aggregation in order to attract females reaching sexual maturity within the confines of that population. This is seen as an alternate to male aggregations attracting females from outside their boundary.     

Systematics and phylogeny of Parapholidoptera (Orthoptera: Tettigoniidae: Tettigoniinae)

Genus Parapholidoptera is revised and three species, P. yoruka sp.n., P. bolkarensis sp.n. and P. salmani sp.n., are described. Parapholidoptera delineata Stolyarov is placed in synonymy with P. ziganensis Karaba?. Parapholidoptera bodenheimeri Karaba? and P. distincta bodenheimeri Karaba? are placed in synonymy with P. distincta (Uvarov). Parapholidoptera flexuosa Karaba?, previously a subspecies of P. castaneoviridis (Brunner von Wattenwyl), is recognized as a separate species. A key to world species is provided. Cladistic analysis revealed the monophyly of the genus with two major clades. A short account of distribution is presented.     

Acoustic Signals of Katydids of the Tribe Gampsocleidini (Orthoptera,Tettigoniidae) in Russia

Entomological Review - Temporal patterns and frequency spectra of the acoustic calling signals of males of Uvarovites inflatus and four species of the genus Gampsocleis occurring in Russia are...     

The egg-laying habits of Euthypoda acutipennis Karsch (Orthoptera:Tettigoniidae)

The egg-laying habits of the West African bush-cricket (Euthypora acutipennis Karsch) are described. In addition, from a population of females bred in the laboratory, the longevity of the species has been determined.