The reproductive strategy and the vibrational duet of the leafhopper Empoasca vitis

The recent description of a new vibrational mating disruption method to control the leafhopper Scaphoideus titanus Ball opened questions about its possible application to other leafhopper pests. Since the prerequisite for the method＇s successful application is a deep knowledge of the species mating behavior and the exact role of associated signals, we conducted behavioral assays on the green leafhopper Empoasca vitis Gothe, a pest of grapevine and other crops in Europe and Asia. Laser vibrometer recordings of single and paired individuals （male and female） during a 24-h period enabled us to detect and describe 2 male and 1 female signal. The pair formation starts when the female replies to a male call and a duet is established, then it continues through 2 different behavioral stages： Location and Courtship. The proper courtship begins only when the male locates the female. The latter is characterized by a significant change in temporal parameters that regards both the signals and the duet structure. Although the male calling activity and the female replying rate were the same during the 24 h, a lower number of matings was recorded during the night. We discuss the possible role of vision and of the species ecology as factors of reproductive success and mating strategy. Our conclusion is that the mechanical mating disruption technique seems feasible for future application to this species.

Wing buzzing as a mechanism for generating vibrational signals in psyllids (Hemiptera: Psylloidea)

Psyllids,or jumping plant lice(Hemiptera:Sternorrhyncha:Psylloidea),are a group of small phytophagous insects that include some important pests of crops world-wide.Sexual communication of psyllids occurs via vibrations transmitted through host plants,which play an important role in mate recognition and localization.The signals are species-specific and can be used to aid in psyllid taxonomy and pest control.Sev-eral hypotheses have been proposed for the mechanism that generates these vibrations,of which stridulation,that is,friction between parts of the forewing and thorax,has re-ceived the most attention.We have investigated vibrational communication in the Euro-pean pear psyllid species Cacopsylla pyrisuga(Foerster,1848)using laser vibrometry and high-speed video recording,to directly observe the movements associated with signal pro-duction.We describe for the first time the basic characteristics of the signals and signal emission of this species.Based on observations and analysis of the video recordings us-ing a point-tracking algorithm,and their comparison with laser vibrometer recordings,we argue that males of C.pyrisuga produce the vibrations primarily by wing buzzing,that is,tremulation that does not involve friction between the wings and thorax.Comparing observed signal properties with previously published data,we predict that wing buzzing is the main mechanism of signal production in all vibrating psyllids.

Female answer specificity to male drumming calls in three closely related species of the stonefly genus Zwicknia (Plecoptera: Capniidae)

This study examines the rate of female answers to conspecific versus heterospecific male vibratory calls in three,closely related stonefly species:Zwicknia bifrons,Z.acuta,and Z.rupprechti.In a previous study those three species were recognized on the basis of their distinct male drumming calls along with differences in genital morphology and genetic divergence.During this study no-choice playback experiments using original male call samples from each species were performed,and the answer rate of females to con・specific and heterospecific signal variants was measured.Mixed effect logistic regression models were used to test if male call species identity had a statistically significant effect on female answer probability.Females answered conspecific male calls with significantly higher probability than heterospecific calls in all the three examined species,suggesting that the divergence of vibrational communication can be an important component of the prezygotic isolation between them.Low,but well detectable responsiveness to heterospecific calls was observable between Z.bifrons and Z.acuta,the two species closest to each other regarding mitochondrial genetic divergence and male call pattern similarity.Thus,our results are most congruent with a tight,gradual coevolution of male calls and female preferences.

Mating behavior of Psammotettix alienus （Hemiptera： Cicadellidae）

The Wheat dwarf virus, the causal agent of the wheat dwarf disease, is trans- mitted by leafhoppers from the genus Psammotettix and currently the main protection strategy is based on the use of insecticide treatments. Sustainable management strategies for insect vectors should include methods that are targeted to disrupt reproductive behavior and here we investigated the mating behavior of Psammotettix alineus （Dahlbom 1850） in order to determine the role of vibrational signals in intra-specific communication and pair formation. Both genders spontaneously emit species- and sex-specific calling songs that consisted of regularly repeated pulse trains and differ primarily in pulse train duration and pulse repetition time. Females preferred the conspecific male calling song. After a coordinated exchange of pulse trains, the male approached the stationary female. During the close range courtship and also immediately prior to copulatory attempts distinct male vibrational signals associated with wing flapping and wing vibrations were recorded from the substrate. In the presence of a receptive female, competing males emitted vibrational signals most likely aimed to interfere with male-female interaction. Mated females re- gained sexual receptivity after they laid eggs. Although results suggest that the viruliferous status of insects may have an effect on vibrational songs, our current results did not reveal a significant effect of virus on leafhopper performance in mating behavior. However, this study also suggests, that detailed understanding ofplant-vecto^virus interactions relevant for vector mating behavior is essential for trying new approaches in developing future control practices against plant viruses transmitted by insect vectors.