Our results demonstrate that magnetism is nearly ubiquitous across bees and that putative magnetoreception is not restricted to eusocial bee species or bees from a single taxonomic family. Instead, ferromagnetism was found in different bee species exhibiting a wide range of nesting and social behaviors, as well as cleptoparasitism, and in both males and females. Most (87.5%) of the bee species we assessed exhibited a discernable sigmoidal response indicating the presence of ferromagnetic particles, and most met the threshold for putative magnetoreception, based on values of MS and MS/m for S. quadripunctata for which magnetoreceptive behavior has been demonstrated (28, 55). Even beyond the bees, in the outgroups we assessed, we detected significant magnetism, including magnetoreceptive potential in solitary (Cerceris clypeata, Bembix sp., Lissonota sp., and Passaloecus sp.) and eusocial wasps (Polistes carolina), along with flies (Syrphidae).

We also observed several nonmagnetic insects outside of the bee families, including a beetle (Chauliognathus pensylvanicus), other social and solitary wasps, and some flies, and overall lower levels of magnetic signal in the non-bee specimens we evaluated. On the other hand, our sampling of these non-bee groups was superficial and does not represent their evolutionary diversity more broadly, especially given the lack of phylogenetic signal, and even individual variance in magnetic signal within our more well-sampled taxa. Other work has demonstrated magnetoreception in some members of these groups; for example, the beetle species Tenebrio molitor has been shown to exhibit magnetoreception (37).