Abstract:
Eusocial insect colonies form superorganisms, in which nestmates cooperate and use social immunity
to combat parasites. However, social immunity may fail in case of emerging diseases. This is the case
for the ectoparasitic mite Varroa destructor, which switched hosts from the Eastern honeybee, Apis
cerana, to the Western honey bee, Apis mellifera, and currently is the greatest threat to A. mellifera
apiculture globally. Here, we show that immature workers of the mite’s original host, A. cerana, are
more susceptible to V. destructor infestations than those of its new host, thereby enabling more
efficient social immunity and contributing to colony survival. This counterintuitive result shows that
susceptible individuals can foster superorganism survival, offering empirical support to theoretical
arguments about the adaptive value of worker suicide in social insects. Altruistic suicide of immature
bees constitutes a social analogue of apoptosis, as it prevents the spread of infections by sacrificing
parts of the whole organism, and unveils a novel form of transgenerational social immunity in honey
bees. Taking into account the key role of susceptible immature bees in social immunity will improve
breeding efforts to mitigate the unsustainably high colony losses of Western honey bees due to V. destructor
infestations worldwide.
