The bacteria that cause Lyme disease are transmitted to humans primarily by the blacklegged tick (Ixodes scapularis). Often presumed guilty by association is the lone star tick (Amblyomma americanum). However, a new review of three decades’ worth of research concludes the latter should be exonerated: While lone star ticks are guilty of transmitting bacteria that cause several human illnesses, the scientific evidence says Lyme disease is not one of them.