Ornithodoros sparnus sp. n., a Parasite of Wood Rats, Neotoma spp. and Deer Mice, Peromyscus spp. in Utah and Arizona (Acarina : Argasidae)

Abstract

Ornithodoros ticks associated with wood rats, Neotoma lepida lepida Thomas; N. cinerea (Ord); deer mice, Peromyscus maniculatus (Wagner); and P. crinitus (Merriam), in Utah have previously been referred to as 0. hermsi Wheeler, Herms, and Meyer. These ticks and specimens from Arizona have been found to represent a separate species and the name 0. sparnus sp. n. is proposed for them. Adults and immature stages are described. Although the adults and nymphs strongly resemble those of 0. hermsi, the larvae are morphologically and biologically distinct. The presence of adult and nymphal ticks, provisionally determined as Ornithodoros hermsi Wheeler, Herms, and Meyer, 1935 by Kohls, in nests of the desert wood rat, Neotoma lepida lepida Thomas, in Utah was reported by Beck, Bamum, and Moore (1953). Results of a seasonal study of populations of this tick in wood rat nests were presented by Beck and Allred (1955) and distributional and host data were given by Beck (1955). Davis and Mavros (1956) found that the Utah ticks differed biologically from 0. hermsi from other western states and that they failed to transmit Borrelia hermsii from California which was readily transmitted by 0. hermsi from Oregon and other states. They concluded that If the Utah ticks are 0. hermsi and not a new species, this is the first marked biological variant in ticks of this genus reported from the western hemisphere. We have found that larvae reared from the Utah ticks are morphologically distinct from those of 0. hermsi and because of this and the biological differences observed by Davis and Mavros, we conclude that these ticks are not 0. hermsi but a new species which is described below. All measurements given are in millimeters. Ornithodoros sparnus sp. n. ADULT: Male and female (Figs. 1 to 4) similar but differing in size and slight secondary sexual characteristics. Received for publication 25 June 1963. * From U. S. Department of Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Institute of Allergy and Infectious Diseases, Rocky Mountain Laboratory, Hamilton, Montana. Body: Oval, wider behind, pointed anteriorly. Females (13 measured) range in size from 2.97 to 3.90 long by 1.74 to 2.15 wide. Males (27 measured) range from 2.32 to 3.17 long by 1.26 to 1.84 wide. Mammillae numerous, moderate in size; the individual mammillae elongated, not conical, with sinuous radiating ridges on the sides; longer axes longitudinal in the lateral areas but tending to be concentric around the discs and groups of discs; about equal in size on the dorsal surface, smaller in the median areas than at the sides ventrally. Setae few, short, and fine. Discs shallow, small, inconspicuous. Legs short, small, surface not micromammillated. Coxae I and II separated, the others contiguous. All tarsi without humps but each usually with a mild subapical dorsal protuberance. Hood well developed as an anterior extension above the capitulum and continuous with the anterior extension of the dorsal body wall. Camerostome deep posteriorly, becoming shallow anteriorly, scarcely visible in fully fed specimens. Cheeks absent. Capitulum: Basis capituli approximately as long as broad, surface irregular with transverse wrinkles; 4 or 5 minute setae situated laterally on each side. Hypostome approximately 0.13 long (measured from bases of posthypostomal setae to apex), notched apically. Posthypostomal setae almost as long as the hypostome. Denticles arranged 2/2; principal denticles limited to distal one-third, about 4 or 5 in each file; corona with 3 to 5 minute denticles on each half. Palpi extending beyond apex of hypostome by length of segment 4; segments 2, 3, and 4 each shorter than segment 1 and subequal in length. Eyes absent. Coxal and supracoxal folds present. Dorsoventral groove absent. Preanal, transverse postanal, and median postanal grooves present, distinct; the transverse postanal groove interrupted by the median postanal groove which extends from near the anus to near the posterior border. Genital aperture at level of base of coxa I. Anus in an elliptical frame. Spiracular plates laterad of coxae IV.