IXODES (IXODES) SCAPULARIS (ACARI, IXODIDAE) - REDESCRIPTION OF ALL ACTIVE STAGES, DISTRIBUTION, HOSTS, GEOGRAPHICAL VARIATION, AND MEDICALAND VETERINARY IMPORTANCE

The blacklegged tick, Ixodes (Ixodes) scapularis Say 1821, is redescri bed, based on laboratory reared specimens originating in Bulloch Count y, Georgia. Information on distribution, host associations, morphologi cal variation, and medical/veterinary importance is also presented. A great deal of recent work has focused on this species because ii is th e prinicipal vector of the agent of Lyme disease (Borrelia burgdorferi Johnson, Schmidt, Hyde, Steigerwaldt & Brenner) in eastern North Amer ica. Its;distribution appears to be expanding, and includes the state of Florida in the southeastern United Stales north to the provinces of Nova Scotia and Prince Edward Island, Canada, west to North and South Dakota, United States, and south to the state of Coahuila, Mexico. Al though I. scapularis Feeds on at least 125 species of North American v ertebrates (54 mammalian, 57 avian, and 14 lizard species), analysis o f the U.S. National Tick Collection holdings show that white-tailed de er, Odocoileus virginianus (Zimmermann), cattle, Bos taurus L., dogs, Canis lupus L., and other medium-to-large sized mammals are important hosts for adults as are native mice and other small mammals,certain gr ound-frequenting birds, skinks, and glass lizards for nymphs and larva e. This tick is a polytypic species exhibiting north-south and east-we st morphological dines. Analysis of valiance and Student-Newman-Keuls multiple comparisons revealed significant interpopulational variation that is expressed most significantly in the nymphal stage. Nymphs from northern (Minnesota, Massachusetts, Maryland) populations had relativ ely larger basis capituli with shorter cornua (except Maryland) than s outhern (North Carolina, Georgia) populations, Midwestern populations (Minnesota, Missouri) differed from eastern populations (Massachusetts , Maryland, North Carolina, Georgia) in idiosomal characters (broader scuta, larger coxae III, and IV). In addition to Lyme disease, this ti ck is also a primary vector of the agent of human and rodent babesiosi s, Babesia microti Franca. Under laboratory conditions it has transmit ted the agents of deer babesiosis, Babesia odocoilei Emerson & Wright, tularemia, Francisella tularensis McCoy & Chapin, and anaplasmosis, A naplasma marginale Theiler. Moreover, I. scapularis can reach pest pro portions on livestock, and females can cause tick paralysis in dogs.