Novel approaches to study vibrational signaling of insects
Creators: name: Akassou, Imane
Publisher: name: Universit� degli studi di Trento
Year: 2021

description: 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.