Infection of Argas (Persicargas) arboreus with the virus of St. Louis encephalitis (SLE) was attempted. Only a low proportion became infected and transmission by bite was not accomplished. Infection of nymphs and transstadial transmission of the virus by nymphs was shown once in 9 attempts. Transovarial transmission of the virus was not demonstrated.
Virus was retained in some infected females for at least 52 days, despite failure to transmit. The possibility that other bird-feeding ticks may serve as reservoirs of SLE virus is mentioned.