First record of Tettigonia viridissima Linnaeus, 1758 (Orthoptera: Tettigoniidae) as host of the ormiine Therobia leonidei Mesnil, 1964 (Diptera: Tachinidae)

Invertebrate central neural structures, especially sensory or motor neuropiles, have proved rather intractable to conventional physiological analysis as they are considered to have a diffuse or unordered structure. This is also true for the auditory neuropiles in the ventral nerve cord of orthopterans, where receptor fibres synapse to interneurones. In the bushcricket, Tettigonia viridissima, this neuropile constitutes the terminations of about 40 receptor fibres, which derive from chordotonal receptor cells in the tibia of the foreleg. Zhantiev1 and Rheinlaender2 have shown that each receptor cell is tuned to a ‘best frequency’. Oldfield3 has further shown that the sensilla are organized tonotopically within the organ, the proximal and distal receptors being tuned to low and high frequencies respectively. Besides the finding that auditory receptor axons form a diffuse neuropile on each side of the prothoracic ganglion4,5, there are no data on the projection of single receptor fibres within the neuropile. The results presented here show that the auditory neuropile of T. viridissima is tonotopically organized, extending to within the central nervous system the tonotopic organization of the peripheral sense organ.

Regeneration and reestablishment of synaptic connections is an important topic in neurobiological research. In the present study, the regeneration of auditory afferents and the accompanying effects in the central nervous system are investigated in nymphs and adults of the bush cricket Tettigonia viridissima L. (Orthoptera: Tettigoniidae). In all animals in which the tympanal nerve is crushed, neuronal tracing shows a regrowth of the afferents into the prothoracic ganglion. This regeneration is seen in both adult and nymphal stages and starts 10–15 days after nerve crushing. Physiological recordings from the leg nerve indicate a recovery of tympanal fibres and a formation of functional connections to interneurones in the same time range. Electrophysiological recordings from the neck connective suggest additional contralateral sprouting of interneurones and the formation of aberrant connections. The regeneration processes of the tympanal nerve in nymphal stages and adults appear to be similar.

The representation of alternative conspecific acoustic signals in the responses of a pair of local interneurons of the bushcricket Tettigonia viridissima was studied with variation in intensity and the direction of sound signals. The results suggest that the auditory world of the bushcricket is rather sharply divided into two azimuthal hemispheres, with signals arriving from any direction within one hemisphere being predominantly represented in the discharge of neurons of this side of the auditory pathway. In addition, each pathway also selects for the most intense of several alternative sounds. A low-intensity signal at 45 dB sound pressure level is quite effective when presented alone, but completely suppressed when given simultaneously with another signal at 60 dB sound pressure level. In a series of intracellular experiments the synaptic nature of the intensity-dependent suppression of competitive signals was investigated in a number of interneurons. The underlying synaptic mechanism is based on a membrane hyperpolarization with a time-constant in the order of 5-10 s. The significance of this mechanism for hearing in choruses, and for the evolution of acoustic signals and signalling behaviour is discussed.

The gall midge Obolodiplosis robiniae is a pest of black locust Robinia pseudoacacia. The species was recently introduced into Europe and it is nowadays a usual insect in Slovakia, where two-year field surveys were undertaken during 2007–2008. The main objective of this study was to determine the natural enemies attacking O. robiniae and estimate their influence on midge population, less than 3 years after its introduction. Eight parasitoids and bushcricket Tettigonia viridissima were responsible for midge regulation. The parasitoid complex was not typically that of an introduced species as it was predicted. Firstly, the midge was heavily influenced by a specialized parasitoid Platygaster robiniae, which was a predominant parasitoid and accounted for 98% of all specimens reared. Secondly, annual larval parasitism varied from 5.4 to 10.8%, though the late season average parasitism achieved 26.0% and often exceeded 40%. P. robiniae was also very efficient in exploiting galls and was capable of consistently regulating midge population. The surveys demonstrated that the average cumulative impact of natural enemies on the midge was substantial. Stably around 20% of attacked galls were recorded during the late summer. Bushcrickets were as efficient as parasitoids and played an important role at control, especially during lack of parasitoids. Greater impact of parasitoids was found in the larger settlements than it was in the countryside, when countertendency was valid for bushcrickets. There is an indication that O. robiniae parasitized by specialized parasitoid, and attacked by bushcrickets represents only a moderate risk for R. pseudoacacia or forest stands.

Insects have developed different structures to adhere to surfaces. Most common are smooth and hairy attachment pads, while nubby pads have also been described for representatives of Mantophasmatodea, Phasmida and Plecoptera. Here we report on the unusual combination of nubby and smooth tarsal attachment structures in the !nara cricket Acanthoproctus diadematus. Their three proximal tarsal pads (euplantulae) have a nubby surface, whereas the most distal euplantula is rather smooth with a hexagonal ground pattern resembling that described for the great green bush-cricket Tettigonia viridissima. This is, to our knowledge, the first report on nubby euplantulae in Orthoptera and the co-occurrence of nubby and smooth euplantulae on a single tarsus in a polyneopteran species. When adhering upside down to a horizontal glass plate, A. diadematus attaches its nubby euplantulae less often, compared to situations in which the animal is hanging upright or head down on a vertical plate. We discuss possible reasons for this kind of clinging behaviour, such as morphological constrains, the different role of normal and shear forces in attachment enhancement of the nubby and smooth pads, ease of the detachment process, and adaptations to walking on cylindrical substrates.

The paper focuses on several species of bush-crickets (Orthoptera, Tettigoniidae) which had not been recorded in central, southern and western parts of the Pskov region, north-western Russia, and were found there for the first time in 2017 and 2018. The bicoloured bush-cricket Bicolorana bicolor (Philippi, 1830) was collected in Sebezhsky district; the sickle-bearing bushcricket Phaneroptera falcata (Poda, 1761) was recorded in Nevelsky district; the great green bush-cricket Tettigonia viridissima L. was recorded in Pushkinogorsky district; the dark bush-cricket Pholidoptera griseoaptera (De Geer, 1773) was recorded in Pechorsky district.