Insect vibrational communication: description, decoding, and manipulation

Vibrations are extremely widespread and ancient among animals’ communication modalities; nevertheless, their importance has been neglected for many years. During my PhD I wanted to increase the knowledge about the role of vibrational signals in insects. Therefore, I conducted behavioral bioassays and laser vibrometer recordings to describe and decipher vibrations produced by four species belonging to two different orders. The role of vibrational signals in intraspecific communication varies widely among different groups of insects. For this reason I chose to study two model groups, Hemiptera and Hymenoptera. Hemiptera, in particular leafhoppers, rely almost exclusively on vibrations for intraspecific communication. Their reproductive strategy is based on the production of vibrational calling and courtship signals, which are necessary for identification and location of the mating partner. Similarly, male-male competition for mating is regulated by means of specific vibrational signals, which in many cases are used to interfere with an ongoing mating duet. The emission of specific disruptive noise gives the rival male a chance to access mating by replacing the calling male in the duet. Recent studies showed that disruptive signals can be played back into plants to effectively disrupt the mating behavior of the grapevine leafhopper, Scaphoideus titanus. These findings inspired my research, its aims and the experimental approach. First, I described and decoded the reproductive strategy and associated vibrational signals of two grapevine leafhoppers species, the green leafhopper, Empoasca vitis and the glassy-winged sharpshooter, Homalodisca vitripennis. Secondly, I used the acquired knowledge to select potential synthetic ‘disruptive signals’ and test their efficacy in disrupting the mating process of E. vitis in laboratory conditions. Hymenoptera, on the other hand, such as paper wasps of the genus Polistes, use mainly semiochemicals to coordinate colony activities (e. g., to discriminate among individuals and their roles). However, the “mechanical switch hypothesis” suggested that vibrations produced by body oscillation movements of foundresses can bias larvae development towards a worker phenotype. That is, when a larva is subjected to low frequency vibrations it will develop into a worker. The social parasite - host system, Polistes sulcifer – P. dominula, was a very good model to investigate the potential caste determination function of body oscillation movements in paper wasps. P. sulcifer, the parasite, does not have a worker caste and its reproductive success rely exclusively on the brood cares provided by the host workers that emerge from usurped colonies. For this reason, I described and compared the vibrations transmitted to the nest by both species in usurped and not-usurped colonies. Moreover, the “mechanical switch hypothesis” predicts that vibrations manipulate larval development by modulating the “nutritional effect” (i.e. larvae that are fed more should develop into reproductive individuals and viceversa). Therefore, I tested the P. dominula foundress ability to modulate the vibration emission in association or not with the feeding activity. This research unveiled remarkable information in both model groups. Several original aspects in the leafhopper mating behavior have been discovered. Main peculiarities have been found in the daily activity and the potential role of visual stimuli in E. vitis, and in the complex structure of signals and male-male rivalry interactions in H. vitripennis. These results showed that multimodal communication (i.e. vision plus vibrations) and ecological adaptations still need to be studied in leafhoppers to fully understand how vibrational signals evolved and adapted to ecological constraints. From an applied point of view, we identified one disruptive signal that, in laboratory conditions, was highly effective in disrupting E. vitis mating process. On the other hand, I described, for the first time in detail, the spectral properties of induced vibrations into a paper wasps nest produced by P. dominula and its social parasite P. sulcifer. By comparing the vibrations produced by P. dominula, in different larval nutritional conditions, and the parasite we found several significant differences. For example, the foundress varies the spectral and temporal properties when she is feeding the larvae; while the parasite produces vibrational events with some exaggerated features compared to the host (i.e. each event is composed of a higher number of pulses). Results have been discussed from an adaptive point of view considering the putative role of vibrations in leading larvae caste determination. Overall, this thesis provides novel insights on the great variability of functions and adaptations of vibrational signals. The acquired knowledge can be used as a basis to perform further experiments on biological and applied aspects of biotremology

Vibrational calling signals improve the efficacy of pheromone traps to capture the brown marmorated stink bug

Halyomorpha halys (Stål, 1855), the brown marmorated stink bug (BMSB), is an invasive species that has become a key agricultural pest in its invaded range. Commercial traps available for BMSB monitoring rely on male produced aggregation pheromones as lure, with two possible shortcomings: trap spillover and low detection precision. In this study, we assessed if vibrational signals can increase the attractiveness of pheromone traps by testing the optimized vibration-based lure (Female Song 2, FS2) associated with a specifically designed trap (i.e., the vibrotrap). We evaluated the efficacy of this bimodal trap (i.e., pheromones + vibrations) on females, males and nymphs in controlled conditions (greenhouse) and in the field, in two sites at the margin of two commercial vineyards. In the field, bimodal vibrotraps were compared to three unimodal (i.e., only pheromone) trap types. Both experiments showed that the vibrotrap is highly attractive for BMSB, and the optimized FS2 signal significantly improved its effectiveness. Even though FS2 was selected to target males, the number of trapped females increased as well. Overall, the presented findings show a feasible improvement to future commercial BMSB traps through the synergic use of semiophysicals and semiochemicals. Further research is needed to evaluate the effectiveness of vibrotraps for both early detection and mass trapping

Detection and characterization of incidental vibrations from Drosophila suzukii in infested fruits

The spotted-wing drosophila (SWD), Drosophila suzukii (Matsumura), is an invasive species native to East Asia and now widespread worldwide. Major economic damage is caused by the larvae developing within ripening soft-skin fruit. Currently, larval detection in fruit is limited to destructive methods and post-harvest control strategies heavily rely on the use of chemicals or cold to inhibit egg eclosion and larval growth. Feeding larvae are likely to induce substrate-borne vibrations in the berry that could be exploited as cues by predators or to develop a non-invasive pest detection method, an approach previously applied on leaves and wooden structures, but never on fresh fruit. We used a laser vibrometer to detect and characterize the incidental vibrations produced by D. suzukii larvae within fresh blueberries at five different pest age (48, 96, 168, 216 and 264 h). An innovative statistical analysis was performed to assess if infestation level (number of pupae) and pest age (hours after exposure) affect the spectrum and the amplitude of vibrations. The recordings of infested berries were characterized by the presence of a series of broad-band pulses (frequency range 0.1–2 kHz) without a regular temporal pattern, in an amplitude range between 12.1 and 946 μm/s. Furthermore, the analysis revealed the possibility to distinguish between different pest ages and infestation levels. By a spectral analysis of the recordings, the pest ages can be distinguished among each other, but for the age groups at 168 and 216 h after infestation. The vibration amplitude trend gradually increased up to 168–216 h after infestation, and then decreased until fly emergence. Low-infested blueberries showed a faster D. suzukii development time compared to high-infested blueberries. This was reflected into vibrational recordings, as low-infested blueberries exhibited peak amplitude at earlier stage compared to high-infested ones. Results suggest that D. suzukii larvae induce detectable vibrations by feeding within berries that are dependent on infestation level and pest age. We discuss the possible ecological role of such vibrations as cues for unintended receivers, such as predators and parasitoids, and their potential for innovative infestation detection method

Substrate-borne vibrations produced during the interaction with natural enemies alter aphids probing behavior

The “ecology of fear”, i.e., physiological and behavioral alterations displayed by pests in response to predation risk, has recently been proposed as a sustainable alternative to chemicals for pest control. However, the development of such a strategy requires a detailed understanding of the signals and cues underlying the pest-antagonist interaction and eliciting the prey behavioral alteration. Here, we characterized the substrate-borne vibrations produced during the interaction between the green peach aphid Myzus persicae and its antagonists, the parasitoid wasp Aphidius colemani and the ladybug Adalia bipunctata. Thereafter, coupling the electrical penetration graph (EPG) with a stimulus controller, we evaluated whether the playback of the vibrations, alone and in combination with the alarm pheromone, impacted aphid probing behavior and interaction with the host plant. Aphids responded to vibrations exhibiting longer non-probing, shorter intracellular probes, i.e. the behavior through which the insect evaluates host plant quality, delay in accessing the phloem vessels and decrease of the frequency of phloem salivation events. In contrast, on plants treated with the alarm pheromone, insects displayed longer intracellular probes. We hypothesize that the alarm pheromone, signaling a distant threat, might induce a careful evaluation of the host plant in order to decide the magnitude of the reaction. On the other hand, vibrations might indicate a closely approaching threat pushing the aphid to rush the host evaluation process and the whole feeding process. The possible repercussion of the behavioral alterations observed on the dynamics of aphid-borne plant virus transmission is also discusse

Intruding into a conversation: how behavioral manipulation could support management of Xylella fastidiosa and its insect vectors

Behavioral manipulation (BM) is a multimodal control approach based on the interference with the stimuli mediating insect perception and interaction with the surroundings. BM could represent a win–win strategy for the management of vector-borne plant pathogens as the bacterium Xylella fastidiosa, since it could reduce the number of vectors alighting on host plants and, consequently, the chances for transmission to occur. In this review, we summarized current knowledge and highlighted gaps in information on (i) how insect vectors of X. fastidiosa in general, and more specifcally the meadow spittlebug Philaenus spumarius, locate and accept the host plant; and (ii) how behavioral manipulation techniques could be applied to disrupt the vector–host plant interaction. Finally, we discussed how diverse BM strategies could be combined with other integrated pest management tools to protect olive groves from inoculation with the fastidious bacterium

REBALANCING DISRUPTIVE BUSINESS OF MULTINATIONAL CORPORATIONS AND GLOBAL VALUE CHAINS WITHIN DEMOCRATIC AND INCLUSIVE CITIZENSHIP PROCESSES- REVIEW WORKING PAPER

The purpose of this working paper is to conduct a comprehensive review of existing literature that explores the relationship between business organizations and democracy. This review draws from various fields, including management, business ethics, sociology, international law, and other relevant disciplines for this Project and has several objectives. Firstly, it aims to provide insight into prior research on how democratic institutions regulate economic actors and how these actors, particularly large multinational corporations (MNCs), resist such regulation. Additionally, it examines how these economic actors develop behaviors and economic models that pose challenges to democratic governance, such as business-related human rights violations. In the initial part of the review, we delve into the historical and contemporary aspects of the relationship between business and democracy. Furthermore, the report explores how companies can contribute to shaping a more democratic future by addressing gaps in governance, especially in cases where populist governments fail to protect the rights of their citizens. It also considers the development of alternative business models, such as social enterprises and cross-sector partnerships. Moreover, it looks into how businesses can actively engage in democratic governance and promote principles of participation. The final section of the working paper involves a bibliometric analysis, including co authorship, co-citation, and keyword co-occurrence maps. This analysis is based on key references used by team members in their literature reviews and is designed to examine the connections that exist among various strands of research that support the research questions of the Rebalance Project

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

2restrictedInternationalThe 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 speciesrestrictedNieri, R.; Mazzoni, V.Nieri, R.; Mazzoni, V

Disrupting pest reproduction techniques can replace pesticides in vineyards. A review

Today, we are faced with an increase in the impact of pesticides on the environment, which is becoming a real concern for most agricultural production systems, including vineyards, for a number of reasons, such as the resistance of pest populations to pesticides, the lethal and sublethal efects of pesticides on non-target species, the increase in new invasive pests, the extension of the geographical range of pests due to climate change, and, fnally, human health problems. Against this backdrop, the adoption of solutions based on the reproductive behavioral ecology of pests is a subject of prominent (major) interest for the coming decades. Crop pests and, more specifcally, disease vectors use sensory cues throughout their life cycle for many fundamental behaviors and in particular for mating, the critical step in population growth. In particular, a large proportion of arthropod crop pests rely on chemical and/or vibroacoustic communication to mate. Several thousand sex pheromones have been identifed in insects, most of which can be used either as synthetic baits to trap pests or as behavioral modifers (e.g., pheromone-mediated mating disruption). Applied biotremology is also emerging as a new discipline for sustainable pest control. Field experiments on vibratotional mating disruption against grapevine leafhoppers are currently ongoing, with promising results. Here we present mating disruption strategies that can be implemented in crop protection, in particular against the main pests and vectors present/occurring in grape productio