Influences of Relatedness, Food Deprivation, and Sex on Adult Behaviors in the Group‐living InsectForficula auricularia

Abstract

The evolution of group living is generally associated with the emergence of social behaviors that ensure fitness benefits to group members. However, the expression of these behaviors may depend on group composition, which can vary over time with respect to sex, starvation status, and relatedness. Here, we investigated (1) whether adults of the group-living European earwig, Forficula auricularia, show cooperative behaviors toward conspecifics and (2) whether sex, food availability, and relatedness shape the nature and frequency of these behaviors. We conducted a full-factorial experiment using 108 unisexual pairs of adults, in which we manipulated these three factors and video-recorded the earwig behaviors for 45 min. Our results revealed that adults mostly expressed self-directed and aggressive behaviors. Nevertheless, they also showed allogrooming, a social behavior that offers scope for cooperation. Pairs of males displayed longer bouts of aggression and allogrooming (when it occurred) than pairs of females. Food deprivation had no effect on male behaviors, but females spent less time self-grooming and walking when they were food deprived. Finally, low relatedness between adults did not influence any of the measured behaviors, but exacerbated frass production, possibly due to social stress. Overall, these results indicate the limited role of cooperation among F. auricularia adults during their group-living phase.

Survival after pathogen exposure in group‐living insects: don't forget the stress of social isolation!

“…All animals were bred under the standard laboratory conditions detailed in Weiß et al . (). The pre‐exposure treatments took place two months after adult emergence, by transferring 359 virgin adults to Petri dishes either alone ( N isolated females = 36, N isolated males = 35) or in experimental groups of four unrelated individuals of the same sex ( N groups of females = 39, N groups of males = 33).…”

“…Here, we investigated whether the benefits of DDP, the benefits of social immunity (through interactions with group members) or the cost of social isolation determined the survival of pathogen‐exposed adults in the European earwig Forficula auricularia . In this insect species, adults form groups with a size range from pairs to several dozens of individuals (Costa, ; Suckling et al ., ), in which they express social behaviours such as allogrooming (Weiß et al ., ) – a common mediator of social immunity (Reber et al ., ). Our experiment consisted in monitoring the survival rate of group‐living female and male adults that were exposed either to the common entomophagous fungus Metarhizium brunneum or to a control solution.…”

Condition-Dependent Trade-Off Between Weapon Size and Immunity in Males of the European Earwig

“…The Petri dishes were furnished with moist sand and maintained under standard laboratory conditions 49 . All morphometric measurements were done following standard protocols 27 , 47 , 50 , in which sizes were taken to the nearest 0.001 mm using the Leica Application Suite 4.5 software (Leica Microsystems, Wetzlar, Germany) on pictures of CO 2 anesthetized males taken under a binocular scope (Leica, MZ 12.5).…”

Social immunity and the evolution of group living in insects

“…This behaviour is ubiquitous in eusocial insects [87], in which it reduces the presence of external parasites on the receiving individual, as well as improving the immune response of the donor through low dose infection [70]. Allogrooming has also been reported in non-eusocial insects, such as earwigs and cockroaches [72,88], but its importance in reducing parasite infection remains unclear. Note that the mediator of social fever is also not specific to eusocial systems.…”