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Social insects' nests harbor intruders known as inquilines, 1 which are usually related to their hosts. 2 , 3 However, distant non-social inquilines may also show convergences with their hosts, 4 , 5 although the underlying genomic changes remain unclear. We analyzed the genome of the wingless and blind bee louse fly Braula coeca, an inquiline kleptoparasite of the western honey bee, Apis mellifera. 6 , 7 Using large phylogenomic data, we confirmed recent accounts that the bee louse fly is a drosophilid 8 , 9 and showed that it had likely evolved from a sap-breeder ancestor associated with honeydew and scale insects' wax. Unlike many parasites, the bee louse fly genome did not show significant erosion or strict reliance on an endosymbiont, likely due to a relatively recent age of inquilinism. However, we observed a horizontal transfer of a transposon and a striking parallel evolution in a set of gene families between the honey bee and the bee louse fly. Convergences included genes potentially involved in metabolism and immunity and the loss of nearly all bitter-tasting gustatory receptors, in agreement with life in a protective nest and a diet of honey, pollen, and beeswax. Vision and odorant receptor genes also exhibited rapid losses. Only genes whose orthologs in the closely related Drosophila melanogaster respond to honey bee pheromone components or floral aroma were retained, whereas the losses included orthologous receptors responsive to the anti-ovarian honey bee queen pheromones. Hence, deep genomic convergences can underlie major phenotypic transitions during the evolution of inquilinism between non-social parasites and their social hosts., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The neuropeptide F (NPF) and its short version (sNPF) mediate food- and stress-related responses in solitary insects. In the honeybee, a social insect where food collection and defensive responses are socially regulated, only sNPF has an identified receptor. Here we increased artificially sNPF levels in honeybee foragers and studied the consequences of this manipulation in various forms of appetitive and aversive responsiveness. Increasing sNPF in partially fed bees turned them into the equivalent of starved animals, enhancing both their food consumption and responsiveness to appetitive gustatory and olfactory stimuli. Neural activity in the olfactory circuits of fed animals was reduced and could be rescued by sNPF treatment to the level of starved bees. In contrast, sNPF had no effect on responsiveness to nociceptive stimuli. Our results thus identify sNPF as a key modulator of hunger and food-related responses in bees, which are at the core of their foraging activities., Competing Interests: The authors declare that they have no competing interests., (© 2021 The Authors.)

Social learning is taxonomically widespread in the animal kingdom [1], and although it is long thought to be a hallmark of vertebrates, recent studies revealed that it also exists in insects [2-5]. The adaptive functions of social learning are well known, but its underlying mechanisms remain debated [2, 5, 6]. Social insects critically depend on the social transmission of information for successful food search and their colonies' fitness [7] and are tractable models for studying the social cues and cognitive mechanisms involved [2-5]. Besides the well-known dance language allowing them to communicate the location of food sources among nestmates [8], honeybees also learn chemosensory information about these sources both outside and within the hive [9, 10]. In the latter case, they associate the floral scent carried by returning foragers on their body with the nectar provided through mouth-to-mouth trophallaxis, similar to the manner in which foragers directly learn odorant-nectar reward associations at the foraging patch [9-11]. Strikingly, however, neither the dance nor trophallaxis is strictly necessary for foragers recruited within the hive to find the right floral source, and simple body contact between foragers may be sufficient [12]. What is the reinforcing agent in this case? We show here that simple social contact acts as appetitive reinforcement and can be used in associative olfactory learning. We demonstrate that this social reinforcement is mediated by bees' antennal movements and modulated by bees' behavioral development. These results unveil a social learning mechanism that may play a facilitating role in resource exploitation by social groups., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Olfactory systems dynamically encode odor information in the nervous system. Insects constitute a well-established model for the study of the neural processes underlying olfactory perception. In insects, odors are detected by sensory neurons located in the antennae, whose axons project to a primary processing center, the antennal lobe. There, the olfactory message is reshaped and further conveyed to higher-order centers, the mushroom bodies and the lateral horn. Previous work has intensively analyzed the principles of olfactory processing in the antennal lobe and in the mushroom bodies. However, how the lateral horn participates in olfactory coding remains comparatively more enigmatic. We studied odor representation at the input to the lateral horn of the honeybee, a social insect that relies on both floral odors for foraging and pheromones for social communication. Using in vivo calcium imaging, we show consistent neural activity in the honeybee lateral horn upon stimulation with both floral volatiles and social pheromones. Recordings reveal odor-specific maps in this brain region as stimulations with the same odorant elicit more similar spatial activity patterns than stimulations with different odorants. Odor-similarity relationships are mostly conserved between antennal lobe and lateral horn, so that odor maps recorded in the lateral horn allow predicting bees' behavioral responses to floral odorants. In addition, a clear segregation of odorants based on pheromone type is found in both structures. The lateral horn thus contains an odor-specific map with distinct representations for the different bee pheromones, a prerequisite for eliciting specific behaviors., (Copyright © 2014 Elsevier Ltd. All rights reserved.)