Vibrational communication is one of the oldest modes of communication that represents an important component of animal behavior, yet it is the least explored among the different modalities. The study of substrate-borne vibrations has contributed to the understanding of multiple intra and interspecific interactions in insects. However, despite the increasing research in the field of biotremology, the exchange of vibrational signals in complex communication networks and in ecological contexts represents an understudied dimension of research. Therefore, the aim of the present work is to expand the study of vibrational signaling behavior of insects into more ecological systems, simulating natural situations in which they live and therefore provide more reliable information about their behavior. Different methodologies were applied according to different research questions. The study consisted of continuous recordings with a laser vibrometer of insect communication throughout a specific behavior, in a multiple individuals’ scenario and in natural conditions. Laboratory trials were conducted to reproduce and study the parental care behavior in burying beetles in relation to their stridulations. Comparing the stridulating behavior of Nicrophorus vespilloides between pre- and post-hatching care revealed higher signaling activity in post-hatching and the occurrence of different patterns of signals, which implies that the signals are likely involved in attracting the larvae toward the carrion and/or in coordinating their provisioning. These results raise questions about the exact function of the stridulations in the biparental care behavior of Nicrophorus beetles. Moving to semi-field conditions, individuals of the same sex of the spittlebug Philaenus spumarius have been recorded throughout their adult stage season. We found a higher and delayed vibrational signaling activity of females compared to males and complex intrasexual interactions consisting of signal overlapping in the case of females and signal alternating, partial or complete overlapping in the case of males. Our study has permitted to describe interactions that could mediate cooperative or competitive intrasexual behaviors in this species. Further reasearch is therefore needed to determine the functions of the reported intrasexual interactions. Finally, field recording trials in an organic vineyard showed that low vibrational signaling activity of an insect community was significantly associated with conditions of high temperature and wind velocity. Furthermore, the field recording methodology enabled the temporal monitoring of the agricultural pest Halyomorpha halys and the grapevine leafhopper Scaphoideus titanus. These findings confirm the validity of our method in assessing vibrational signaling in the vineyard and open the possibility to the use of biotremology techniques to detect the presence of insect pests in an orchard as a tool of monitoring. In this way, further research is needed to optimize the methodology to implement it in comparing vibrational signaling in vineyards with different management systems and in different types of orchards. Despite the challenges to use vibrational sensitive equipment in such ecological systems where interferences from noise, studied insects and the environment were encountered, the use of biotremology techniques has been proven feasible. Vibrational signals are better manifested when insects are studied in their natural habitats, interesting results can be obtained, and further questions would be asked for the ultimate understanding of this modality of animal communication. Overall, this thesis provides novel approaches to record and study vibrational signals of insects, which can be used as a basis to perform further experiments in the field of biotremology.

Due to a lack of in-situ methods capable of detecting sub-lethal effects of pollutants on soil organisms, many polluted environments are not identified prior to pollution-induced changes in the soil fauna. Therefore, there is a need to develop new non-invasive methods to measure the health of soil organisms. This study aimed to assess to what extent surface borne vibrations can inform about ant health effects from exposure to sublethal doses of a pesticide (imidacloprid). Twelve ant colonies were set up with artificial nests and fed a glucose and imidacloprid solution (0.01 mg/L, 0.1 mg/L, 1 mg/L and 10 mg/L imidacloprid). After two days, five random ants were placed in an arena where the vibrations were recorded in five one-minute blocks using a Laser Doppler Vibrometer (LDV). No significant difference was found in activity per minute between the different concentrations, although there was a measurable increase in mortality between the concentrations from the second day of exposure to the fifth. Even so, the LDV may still be a viable method, as it clearly recorded vibrations caused by ant movement. If more ants were recorded for longer periods, and more replicates were used, it seems likely the method would have been sensitive enough to detect the effect of the studied pesticide. With an improved experiment design, using the LDV for this purpose may be possible, and the current lack of such a method necessitates further research on the subject.

Insects can cause economic and environmental damages by transmitting bacterial pathogens to plants, making the use of control and prevention measures imperative. On the other hand, methods aimed at preventing crop pests’ outbreaks, such as tilling and insecticide applications, pose a threat to human and ecosystems health. Innovative and more sustainable control methods are therefore urgently needed to address farmers’ needs and preserve ecosystem services provided by biodiversity. Biotremology is an emerging science that studies the substrate-borne vibrational signals emitted by insects to communicate and interact with their others in the environment. As many insect pests rely on these signals to communicate, their behaviour can be manipulated by transmitting vibrations to the substrate where they thrive. Vibrational signals can, for instance, interfere with target’s behaviours such as mating, feeding, and residence time on the plant, and can therefore support integrated pest management strategies alternative to insecticides. In this work, I investigated the mating behaviour and vibrational communication of two insect vectors having an important economic impact: Philaenus spumarius (Hemiptera: Aphrophoridae) and Bactericera cockerelli (Hemiptera: Triozidae). I also provided novel insights regarding the vibrational manipulation of their behaviour. I characterised the sexual behaviour and associated vibrational signals of the meadow spittlebug P. spumarius, and I described other intraspecific interactions. I evaluated the correlation between the female signalling activity and development of the reproductive organs, suggesting that a vibrational mating disruption could be effective only if applied from the onset of egg maturation, which triggers the female proceptivity (from August onwards). Besides gathering behavioural data, I used occupancy models to estimate P. spumarius presence and detection probability in Trentino (Northern Italy), a rarely deployed approach to study insect distribution. Site covariates impacted P. spumarius detectability, suggesting that spittlebug presence can be overlooked if detection is not considered. As plant composition influences the presence and abundance of the spittlebug, I studied the association between P. spumarius and its host plants. Such information can support monitoring programs and control strategies aimed at reducing P. spumarius population in crops of interest by shaping the plant composition of the ground cover. After investigating the behaviours and the ecology of the spittlebug, I attempted to disrupt its feeding activity using vibrations, opening the gates for future research. In this regard, I combined for the first time biotremology with the Electrical Penetration Graph (EPG) technique. The tomato potato psyllid B. cockerelli is an important threat to New Zealand crops. Besides the characterisation of the pair formation process and associated vibrational signals, I used vibrations to disrupt mate finding by transmitting vibrations to the host plant. Given that the stimulus attracted male psyllids at small scale, this strategy is a feasible approach that could be implemented for use in fields and greenhouses. In this way, an innovative trapping and mating disruption device could join the farmers’ toolbox for monitoring and controlling B. cockerelli. In conclusion, I provided new information regarding the ethology of two insect vectors and suggested that there is room for applied biotremology to support sustainable management strategies.

While substrate-borne vibrations are utilized by different reptile species, true conspecific communication via biotremors has not yet been demonstrated in reptiles. This study follows a preliminary report that the veiled chameleon (Chamaeleo calyptratus) could produce biotremors in communicative contexts. I tested chameleon behavioral sensitivity to vibrations by placing them on a dowel attached to a shaker emitting vibrations of 25, 50, 150, 300, and 600 Hz and then measured their changes in velocity before and after the stimulus. I then paired chameleons in various social contexts [anthropogenic disturbance (human disruption of animal); dominance (malemale; female-female C. calyptratus); courtship (male-female C. calyptratus); heterospecific (C. calyptratus + C. gracilis); and predator-prey (adult + juvenile C. calyptratus)] and used a video camera and accelerometers to record their behavior. This study demonstrates that chameleons produce biotremors and that receivers exhibit a freeze response when exposed to a simulated biotremor stimulus. Furthermore, veiled chameleons produce biotremors in anthropogenic disturbance, conspecific dominance and courtship contexts, and these biotremors are elicited by visual contact with another adult conspecific and heterospecifics. Overall, two classes of biotremor were identified, "hoots” and “rumbles,” which differ significantly in dominant frequency and waveform. No correlation was identified between animal size and dominant frequency of the biotremors they produced as biotremors originate from rapid muscle contractions. Juvenile chameleons of two months of age are able to produce biotremors, suggesting this behavior may have multiple functions. Overall, the data suggest that the veiled chameleon has the potential to utilize substrate-borne vibrational communication during conspecific and possibly heterospecific interactions.

cotutelle / La biotrémologie est l’étude de la vibration du substrat (ex. végétal) et de ses effets sur les animaux. En protection des cultures, la vibration du substrat s’utilise à la fois pour dépister les insectes ravageurs de culture et réduire leurs populations. Dans cette étude, nous avons évalué les effets de la vibration du substrat végétal sur l’acceptation de la plante hôte, la rétention, la fécondité et les comportements en période de mue du puceron vert du pêcher Myzus persicae, ravageur important des cultures notamment dans les serres de poivrons. Des vibreurs ont été utilisés en laboratoire pour vibrer le substrat végétal en continu et à une même intensité de 24 h à 48 h. La vibration a réduit l’acceptation des plants vibrés par les pucerons ailés (-75%), comparativement aux plants témoins. Elle a également réduit la rétention des adultes, ailés et aptères (-33 à -46%, respectivement) et de leurs juvéniles (-50 à -65%, respectivement). Ces effets réducteurs ont augmenté avec la durée d’exposition vibrationnelle. Le traitement vibrationnel a eu également comme conséquence de réduire la fécondité des femelles aptères (réduction de 39% des juvéniles:adulte), après exposition au traitement. Les comportements de mobilité ont été plus longs avant la mue, alors que ceux d’alimentation ont été plus courts avant et après la mue chez les juvéniles soumis aux vibrations. La vibration induit un rejet de la plante hôte, réduit la fécondité et altère l’alimentation. La vibration du substrat se profile comme une méthode de lutte mécanique potentielle contre M. persicae. / Biotremology is the study of substrate-bone vibrations (e.g. via plants) and its effects on animals. In crop protection, substrate-borne vibrations are used both to detect crop pests and to reduce their populations. In this study, we evaluated the effects of plant substrate-borne vibrations on host plant acceptance, retention, fecundity and behaviour during the molting period of the green peach aphid Myzus persicae, a major crop pest particularly in bell peppers in greenhouses. Shakers were used in the laboratory to vibrate the plant substrate continuously and at the same intensity from 24 h to 48 h. Vibrations reduced the acceptance of vibrated plants by alate aphids (-75%), compared with control plants. It also reduced the retention of adults, both alate and apterous (-33 to -46%, respectively) and their juveniles (-50 to -65%, respectively). These reducing effects increased with the duration of vibrational exposure. Vibrational treatment also resulted in reduced fecundity of apterous females (reduction of 39% of the juveniles: adult), after exposure to treatment. Mobility behaviours were longer before molting, while feeding behaviours were shorter before and after molting for vibration-treated juveniles. Substrate-borne vibrations induce rejection of the host plant, reduces fecundity and alters feeding. Substrate-borne vibration is emerging as a potential mechanical control method against M. persicae.