Ixodid ticks (Acari, Ixodidae) found in San Diego County, California

In San Diego County, California, 11 species of ixodid ticks were collected from vegetation and/or from small and large mammals, and/or found parasitizing humans. Adults of the Pacific Coast tick, Dermacentor occidentalis, were the most abundant tick collected from vegetation, with peak numbers occurring during March and April. Adults of the Western black-legged tick, Ixodes pacificus, were the second most abundant, with peaks occurring during February and March. Eight species of ticks were found on mammals, with D. occidentalis being the most abundant. Adults of this tick were found primarily on black-tailed deer, Odocoileus hemionus columbianus. Nymphs occurred mostly on larger rodents, particularly the dusky-footed wood rat, Neotoma fuscipes, while larvae preferred mice. Ixodes pacificus was the second most abundant on hosts. Adults of this tick were found mostly on larger mammals, such as carnivores and deer. Nymphs preferred larger rodents, and larvae primarily mice. Five tick species were found on humans. Adults of I. pacificus, mostly females, were the most prevalent and occurred mostly (80.1%) on individuals during October-March, followed by those of Dermacentor variabilis which were found primarily (95.0%) during April-September. Adults of D. occidentalis were the third most prevalent, being found mostly (96.0%) on humans during January-June. Of the ten species of ticks endemic to California found during the survey, two (Ixodes sculptus and Ixodes woodi), have not been previously recorded from San Diego County.