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When females care for broods of mixed paternity, there is a threat of enhanced rivalry among offspring of different paternal lineages. This competition is against the best evolutionary interest of the female because she is equally related to all of her offspring and enhanced offspring competition would decrease her fitness. It was hypothesized earlier that mothers should therefore conceal the information about paternal origin in the recognition cues used by her offspring, for example by transfer- ring the chemical cues used by her offspring for kin recognition. Here, we used a cross- fostering experiment between two closely related and sympatric earwig species, Forficula auricularia and F. decipiens, to demonstrate that F. auricularia nymphs tended by F. decipiens females differ in their cuticular hydrocarbon profiles from F. auricularia nymphs tended by F. auricularia females. This result provides evidence for maternal transfer of cuticular hydrocarbons and shows that offspring adoption across species is possible in earwigs.

In mammals, the chemical profiles of individuals are complex and variable mixtures, and animals perceive information based on variation in the overall quality of these mixtures. A variety of compounds potentially involved in chemical communication have been characterized in the urine of different felid species, but little is known about the information content of felid scent marks. In this study, we investigated whether chemical composition of Eurasian lynx Lynx lynx urine was related to sex, reproductive state, and individual identity. We further analysed if elemental sulphur in lynx urine could serve as a dietary cue or as an indicator for the freshness of a scent mark. We collected urine from captive and wild Eurasian lynx, and analysed volatile constituents of urine by means of solid phase microextraction and gas chromatography-mass spectrometry. Our results show that lynx scent profiles contain sex-specific information on reproductive state, as well as individual identity cues. Urine marks are, therefore, well-suited to fulfil a role in reproductive behaviour and social organisation of wild lynx populations. Relative sulphur content was unrelated to time since last feeding, but decreased with age of the urine sample. The influence of diet and body condition on scent profiles should be further investigated by means of experimental studies, and may shed more light on the messages encoded in carnivore scent-marks.

Many insects raise their offspring on organic substrates or in the soil where microorganisms are abundant. Microbes may pose a serious threat to offspring development and survival by either decomposing food resources or directly infecting the offspring. Selection to cope with these effects may favor social defenses, for example, through forms of parental care that can limit or eliminate these threats to offspring fitness. In this study, we experimentally tested if maternal egg attendance in the European earwig Forficula auricularia has a function as a social defense against mold infection of eggs by manipulating exposure of eggs to mold spores and the presence of the mother in a fully factorial design. Furthermore, we investigated the potential roles of egg grooming behavior and maternal transfer of chemicals as underlying mechanisms. As predicted, the beneficial effect of egg attendance on hatching success was significantly enhanced when eggs were exposed to the mold. Females significantly increased their egg grooming duration in response to mold exposure of her eggs, and the quantity of chemicals (identified as hydrocarbons) was maintained among attended eggs but decreased substantially among unattended eggs. Maternal transfer of chemicals was confirmed in extractions of glass beads that were mingled into attended or unattended clutches. This study shows that maternal egg attendance in the European earwig has a social defense function protecting offspring against mold infection. The maternal egg grooming behavior seems to be key for this effect, probably through both the mechanical removal of spores and the continued application of chemical substances on the egg surface.