Scent-sational drama: Larval chemical signals and the soap opera of insect family dynamics

Family life inherits conflicts between parents and their offspring about the optimal level of parental investment. Theory suggests that the allocation of resources could be affected by offspring signals of nutritional need, which can alter parental investment decisions and therefore resolve the parent-offspring conflict. In insects, social interactions are predominantly mediated by chemical signals, whereby the chemistry of adults can change based on abiotic and biotic factors. Chemical offspring signals and the factors influencing them are far less studied compared to adults. Here, we investigated the changes in volatile organic compounds (VOCs) and cuticular hydrocarbon (CHC) profiles in the larvae of Nicrophorus vespilloides, a beetle species known for its elaborate biparental care, to determine how these changes correlate with the development stage or the nutritional need of offspring. We found that larval cuticular and VOC profiles change with the developmental and nutritional state of offspring. This suggests that larvae can communicate their conditions to their parents, potentially influencing parental care decisions. In addition, our data revealed that second instar larvae – which usually receive more food from their parents than other larval instars - produce the highest levels of specific volatiles, namely acetophenone, octanoic acid isopropyl ester and methyl geranate. Conducting electroantennography (EAG), we found that female antennae react to each of those three larval volatiles. In addition, using a novel bioassay, we were able to show for the first time in burying beetles that maternal feeding trips are induced by larval chemical compounds. Our results suggest that larval odor mediates mother-offspring interactions and may play an important role in the resolution of the parent-offspring conflict in burying beetles. Based on these findings,  burying beetles could be considered a promising candidate for the identification of a potential begging pheromone impacting parental care. Further studies might examine if males also react to the odor of their offspring and further test which begging pheromone candidate may be responsible for shaping family life in burying beetles.