Endosymbiont-derived metabolites are essential for tick host reproductive fitness.

Unlabelled: Ticks, like other obligatory blood-feeding arthropods, rely on endosymbiotic bacteria to supplement their diet with B vitamins lacking in blood. It has been suggested that additional metabolites such as L-proline may be involved in this nutritional symbiosis, but this has yet to be tested. Here, we studied the metabolite-based interaction between the brown dog tick (Acari: Ixodidae) and its like endosymbionts (CLE).