Aggression and defense in honeybees are crucial for deterring predators, sustaining colony homeostasis, and ensuring species reproduction. Studies have shown that aggressive behavior in insects is closely related to key biogenic amines, including octopamine (OA) and dopamine (DA). However, the specific role of OA in modulating honeybee aggression remains largely unknown. In this study, Apis cerana worker bees were injected with OA, an OA receptor agonist (amitraz), an OA receptor antagonist (mianserin), or DA. Workers from a foreign colony were introduced as intruders to quantify aggressive responses, thereby investigating OA's role in aggression. The results showed that injection of OA or OA receptor agonist increased aggression, whereas the OA receptor antagonist caused a reduction. Co-injection of agonist and antagonist abolished the agonist-induced increase, restoring aggression to control levels. DA injection also significantly elevated aggression. These findings demonstrate that aggression in A. cerana is regulated by both OA and DA, with OA acting through its specific receptor system and DA also contributing to the modulation of aggressive behavior.
Ant-aphid mutualism is a classic model in ecology, yet the role of aphid bacterial symbionts in shaping ant foraging remains poorly understood. The aphid symbiont Serratia symbiotica includes free-living strains found in the gut of Aphis fabae aphids. Here, we test whether this gut-associated strain influences early stages of ant foraging and ant-aphid mutualism. We followed two complementary approaches: (i) plant-based assays in which ants initiated foraging on aphid colonies that were infected or not with S. symbiotica, and (ii) assays on individual foragers to disentangle bacterium-driven from aphid-mediated effects on ant behavior. Specifically, olfactometer and feeding assays quantified how S. symbiotica influences long-range attraction and food acceptance by ants, respectively. We found that ants were attracted at a distance to S. symbiotica-infected diets and aphids, indicating enhanced initial forager orientation. However, infected aphid colonies did not increase honeydew collection, trail recruitment, or collective mobilization of ant foragers. Moreover, food acceptance declined at high bacterial concentrations. Overall, S. symbiotica biases early foraging decisions of ants through transient attraction but does not promote sustained foraging investment or enhance ant attendance of aphid colonies.
Intercastes, which exhibit a mosaic of queen and worker traits, provide a unique window into the developmental architecture of caste polyphenism. Here, we report the first discovery of intercastes in the myrmicine ant Aphaenogaster luteipes, based on six individuals that appeared in laboratory colonies. By combining multivariate morphometrics, internal anatomy, and behavioral observations, we characterize the phenotypic structure of these rare forms. Unlike the continuous variation observed in closely related species of A. rugulosa, intercastes of A. luteipes exhibited a strong tendency to form two morphological clusters: a queen-like group and an intermediate group, suggesting distinct patterns of developmental canalization. Crucially, we found a striking dissociation between somatic and reproductive traits. Some large, winged individuals unexpectedly lacked a spermatheca, whereas smaller, wingless intermediates possessed one. This mismatch challenges the strict size-threshold hypothesis, supporting the view that independent developmental modules govern somatic and reproductive traits. Behaviorally, intercastes were not pathological but functional colony members; they actively participated in brood care, and one intercaste produced a trophic egg. These findings highlight the modular nature of phenotypic plasticity and demonstrate how developmental anomalies can serve as raw material for the evolution of novel castes.
Bees are key pollinators that support global food production and plant biodiversity, yet wild pollinator populations are declining due to anthropogenic pressures, including habitat loss, pesticide use, and emerging disease. In honey bees (Apis mellifera), viral disease dynamics have been strongly influenced by the parasitic mite Varroa destructor, which vectors Deformed Wing Virus (DWV) and has altered viral community composition. DWV exists as multiple genotypes, most notably DWV-A and DWV-B, with recent studies suggesting a global shift towards DWV-B dominance. Here, we investigated the prevalence and viral load of DWV-A and DWV-B in honey bees and a wild bumblebee species across ten protected calcareous grassland sites in the UK to evaluate patterns of DWV genotype and the extent of potential pathogen spillover into wild bee populations. Contrary to expectations of DWV-A decline, both genotypes were highly prevalent in honey bees and bumblebees, with frequent co-detections observed. Notably, Bombus lapidarius exhibited higher DWV-A viral loads and similar prevalence to honey bees, indicating a possible role in the maintenance of DWV-A in UK grasslands. These findings challenge assumptions of a shift towards DWV-B predominance and highlight the importance of including wild pollinators in viral monitoring to better understand potential pathogen spillover and multi-host dynamics in managed and wild bee communities.
