Temperature shapes oviposition site selection and post-oviposition egg transport in an insect with parental care

Depositing eggs in an area with adequate temperature is often crucial for mothers and their offspring, as the eggs are immobile and therefore cannot avoid exposure to sub-optimal temperatures. However, the importance of temperature on oviposition site selection is less clear when mothers have the capability to avoid these potential adverse effects by both moving their eggs after oviposition and providing other forms of egg care. In this study, we addressed this question in the European earwig, an insect in which mothers care for the eggs during several months in winter and often move them during this period. Using 60 females from two Canadian populations (St John's and Harvey station) set up under controlled thermal gradients, we demonstrated that earwig females both select oviposition sites according to temperature and move their eggs after oviposition to reach warmer environmental temperatures. While this set of behavioural thermoregulation is present in the two studied populations, its modality of expression was population-specific: St John's females explored greater ranges of temperatures before oviposition, laid their eggs in warmer areas, and moved their eggs quicker toward warm locations. Overall, our study reveals that earwig females have evolved both pre-and post-oviposition behavioural strategies to mitigate the risks inherent to tending eggs during winter. More generally, it also reveals that egg care and egg transport do not prevent behavioural thermoregulation via oviposition site selection and highlights the diversity of behaviours that insects can adopt to enhance their tolerance to global climate change.

The Evolutionary Relevance of Social Learning and Transmission in Non-Social Arthropods with a Focus on Oviposition-Related Behaviors

Research on social learning has centered around vertebrates, but evidence is accumulating that small-brained, non-social arthropods also learn from others. Social learning can lead to social inheritance when socially acquired behaviors are transmitted to subsequent generations. Using oviposition site selection, a critical behavior for most arthropods, as an example, we first highlight the complementarities between social and classical genetic inheritance. We then discuss the relevance of studying social learning and transmission in non-social arthropods and document known cases in the literature, including examples of social learning from con- and hetero-specifics. We further highlight under which conditions social learning can be adaptive or not. We conclude that non-social arthropods and the study of oviposition behavior offer unparalleled opportunities to unravel the importance of social learning and inheritance for animal evolution.

The evolutionary relevance of social learning and transmission of behaviors in non-social arthropods

Research on social learning has centered around vertebrates, but evidence is accumulating that small-brained, non-social arthropods also learn from others. Social learning can lead to social inheritance when socially acquired behaviors are transmitted to subsequent generations. Here, we first highlight the complementarities between social and classical genetic inheritance, using oviposition site selection, a behavior critical for many non-social arthropods, as a hypothetical example. We then discuss the relevance of studying social learning and transmission in non-social arthropods and document known cases in the literature, including examples of social learning from con and hetero-specifics. We subsequently highlight under which conditions social learning can be adaptive or not. We conclude that non-social arthropods and the study of oviposition behavior offer unparalleled opportunities to increase our understanding of social learning and inheritance.

Sex-Specific Oviposition Site Selection and Hatching Success in an Arboreal Treefrog: Implications of a Paternal Nest-Site Selection

Oviposition sites selected by parents is an important factor that affects offspring survival and parental fitness. A good nest site offers offspring protection from competition, predation, and harsh environmental conditions. In amphibians, though oviposition sites are generally determined by females, the distinction between male and female choice can be blurred in species with resource defense mating systems, where males occupy the territory that eggs are deposited before advertising for females. Using a phytotelm-breeding frog (Kurixalus eiffingeri) with male territoriality and biparental care, we examined 310 oviposition sites to determine (1) male choice based on physical characteristics of the site (stump height, inner diameter, stump depth, water depth), and (2) female choice based on site characteristics and male characteristics (snout-vent length and body condition). We hypothesized that either one or both sexes would select oviposition site based on characteristics correlate with higher offspring survivorship. We found that males preferred sites with deeper pools of water, while females showed no preference for sites or males based on the characteristics observed. While we cannot prove any nest traits directly benefit offspring, we contend that increased water depth within the phytotelm may 1) protect male frog from snake predation, which would allow for continued paternal care that increases the hatching success and 2) improve the offspring survival during the larval period. Our findings provide empirical evidence of male-driven oviposition site selection in an amphibian and highlight often overlooked role that males play in increasing their reproductive output by selecting for sites that benefit their offspring.

The predatory bug Orius strigicollis shows a preference for egg-laying sites based on plant topography

Background Oviposition site selection is an important factor in determining the success of insect populations. Orius spp. are widely used in the biological control of a wide range of soft-bodied insect pests such as thrips, aphids, and mites. Orius strigicollis (Heteroptera: Anthocoridae) is the dominant Orius species in southern China; however, what factor drives its selection of an oviposition site after mating currently remains unknown. Methods Here, kidney bean pods (KBPs) were chosen as the oviposition substrate, and choice and nonchoice experiments were conducted to determine the preferences concerning oviposition sites on the KBPs of O. strigicollis. The mechanism of oviposition behavior was revealed through observation and measurement of oviposition action, the egg hatching rate, and the oviposition time. Results We found that O. strigicollis preferred the seams of the pods for oviposition, especially the seams at the tips of the KBPs. Choice and nonchoice experiments showed that females did not lay eggs when the KBP tail parts were unavailable. The rates of egg hatching on different KBP parts were not significantly different, but the time required for females to lay eggs on the tip seam was significantly lower. Decreased oviposition time is achieved on the tip seam because the insect can exploit support points found there and gain leverage for insertion of the ovipositor. Discussion The preferences for oviposition sites of O. strigicollis are significantly influenced by the topography of the KBP surface. Revealing such behavior and mechanisms will provide an important scientific basis for the mass rearing of predatory bugs.

Oviposition by a lycaenid butterfly onto old host parts is adaptive to avoid interference by conspecific larvae

Oviposition site selection by herbivores can depend not only on the quality of host resources, but also on the risk of predation, parasitism and interference. Females of the lycaenid butterfly Arhopala bazalus (Lepidoptera) lay eggs primarily on old host foliage away from fresh growth, where larval offspring live and feed. Resource availability of young host leaves seems not to affect the oviposition site preference by the females. To clarify the adaptive significance of A. bazalus oviposition behavior on old foliage, we tested three hypotheses: eggs on fresh foliage are (1) easily dropped during rapid leaf expansion (bottom-up hypothesis), (2) more likely to be attacked by egg parasitoids (top-down hypothesis), and (3) frequently displaced or injured by other herbivores (interference hypothesis). In field surveys, rates of egg dropping and parasitism by egg parasitoids were not significantly different between fresh and old host parts. However, the portions of fresh leaves on which A. bazalus eggs had been laid were cut from shoots on which conspecific larvae fed. Laboratory experiments demonstrated that eggs on young leaves were displaced in the presence of conspecific larvae and we observed that fifth instar larvae actively displaced conspecific eggs by feeding on the surrounding leaf tissue. These findings indicate that eggs laid on fresh leaves are at risk of being displaced by conspecific larvae, and support the interference hypothesis. Larval behavior is a likely evolutionary force for A. bazalus to lay eggs apart from larval feeding sites on the host plant.