Diapause favors adaptation of organisms to their environment, synchronizing growth and reproduction to seasonal changes, allowing to overcome adverse meteorological conditions (Tauber and Tauber, 1976, Denlinger, 2022). In insects, diapause is characterized by a cessation of morphological development and is genetically controlled and regulated by environmental cues such as temperature, photoperiod and moisture (Denlinger, 2002, Ingrisch, 1984, Ingrisch, 1985, Ingrisch, 1986b). Although many insects terminate diapause within one seasonal cycle, some species can extend diapause period for two or more years (Hartley and Warne, 1972).

To face recurrent temperature changes, tettigoniids (Orthoptera, Ensifera, Tettigoniidae) inhabiting temperate climates overwinter as eggs in a diapause stage, being able to postpone embryogenesis for one or more years (Ingrisch, 1986a, Srygley, 2014). According to the time required for development, life cycle of Western Palearctic tettigoniid species can be divided in: (i) annual, (ii) annual or biennial with facultative diapause, (iii) biennial or longer (up to 8 years due to a prolonged diapause) (Ingrisch, 1986a). However, it is unclear if species living in warmer regions could diapause for a single year or enter a prolonged diapause due to higher summer temperatures. Warmer temperatures experienced by eggs immediately after oviposition could trigger embryonic development, increasing the number of eggs able to develop in just one summer, potentially affecting population dynamics (Ortis et al., 2022). After oviposition (usually between July and October), embryonic development can either be interrupted, even for several years, in a state called initial diapause in the young embryo or triggered until reaching the final diapause stage, where the embryo is mature and occupies the whole egg space (Warne, 1972, Bailey and Rentz, 1990). When final diapause is reached, the egg overwinters for only one winter before completing development and hatching in spring.

Because diapause may influence population dynamics, affect voltinism (Steinbauer et al., 2004) and modify interactions between pathogens and their hosts (Corley et al., 2004), understanding diapause dynamics can help to predict the adaptation of insects to climate change (Tobin et al., 2008, Tougeron, 2019). Most of the previous studies on diapause were carried out under laboratory constant temperatures, that do not reflect the effect of diapause incidence under natural conditions (Colinet et al., 2015, Ortis et al., 2022). The objective of this work was to test the effect of summer temperatures on diapause of several Mediterranean tettigoniid species under natural field conditions. In a two-year experiment, we want to clarify the adaptive strategies of species to seasonal changes that may lead to population fluctuation in certain years.