Brigham Young University Science Bulletin, Biological Series


The principal objective of this study is to bring up to date information on geographic distribution, seasonal occurrence, and host-parasite relationship of O. lagophilus in western North America. Notes on life history and disease transmission potential are included.

Data and information were obtained from three sources: (1) natural history collections and field records at Brigham Young University over the past twenty years; (2) the Rocky Mountain Laboratory in Hamilton, Montana; and (3) published literature.

All available collection records are presented in a table from which information on geographic distribution, seasonal occurrence, and host-parasite relationship was extracted. O. lagophilus is known primarily from the arid and semiarid desert regions of western North America. To a marked extent the known distribution of this tick follows a pattern similar to that of the black-tailed jack rabbit, Lepus californicus descrticola, whose distribution is southern Idaho, most of Nevada, all of Utah except the eastern parts, western Arizona, and the southeastern part of California. The preferred host of O. Iagophilus is L. californicus descrticola, although outside the range of this rabbit most collections have been from L. townsendii and Sylvilagus species. Nymphs have been collected from rabbits in every month of the year, with the peak season in May, June, July, and August. Since most collections have been in the nymphal stage, the peak seasons for larvae and adults are not known.

After emergence from the egg, the larva attaches to the host and feeds until fully engorged, then molts and transforms to a nymph while remaining attached to the same host. The nymph does not drop from the host until it is fully engorged and ready to molt to an adult. The adult, lacking functional mouthparts, is not parasitic and does not feed. Copulation and oviposition take place on the ground.

O. lagophilus has been reported to be naturally infected with Rocky Mountain spotted fever, Colorado tick fever, and tularemia. It has been shown to be capable of harboring the tularemia organism, Pasteurella tularensis, for as long as 676 days. Evidence indicates that O. lagophilus may be a potential reservoir of some diseases in nature, but not a direct vector in transmission from host to host.

Twenty-nine drawings of some external anatomical and morphological features in all stages of development were made as a basis for the construction of a pictorial key for the identification of species in the genus Otobius.