Comparative Morphology of the Life Stages of the Nasal Mite Rhinonyssus rhinolethrum (Mesostigmata: Rhinonyssidae)

Abstract

All the life stages of the mite Rhinonyssus rhinolethrum, a parasite found in the nasal chambers of anatid birds, are described comparatively on the basis of idiosomal sclerotization, chaetotaxy of the idiosoma and legs, ambulacral apparatus, chelicerae, and miscellanea. Morphological differences between the nymphal stages and between the deutonymphal sexes are described. Most of the descriptions of rhinonyssid mites satisfy taxonomic purposes only and usually deal little, if at all, with the immature stages. The only published distinctions between the similar nymphal stages are those of Pereira and de Castro (1949) for a single species of Rhinonyssoides, George (1961) for species of Ptilonyssus, and those of Strandtmann (1961) for species of Ptilonyssus, Paraneonyssus, and Tyranninyssus. The latter publication is the most comprehensive. Immature stages have never before been sexed using characteristics peculiar to the immatures. Much more emphasis should be placed on critical study of the immature stages of these mites by students of the group, not that these are essential in species descriptions, but because a thorough knowledge of the immatures will be essential when aspects of the biology of these mites other than taxonomic become more widely studied than at the present time. This paper presents a detailed comparison of the external morphology of the life stages of Rhinonyssus rhinolethrum (Trouessart) which is parasitic in the nasal chambers of birds of the family Anatidae. Many anatid birds including ducks, geese, swans, mergansers, eiders, Received for publication 26 October 1962. * Supported in part by the Research Committee, Lamar State College of Technology, Beaumont, Texas, and in part by the National Institute of Allergy and Infectious Diseases, NIH Grant No. AI 00616-10, Texas Technological College, Lubbock, Texas. ft Present address: Department of Zoology, The University of Texas, Austin, Texas. and scoters have been reported as hosts by Strandtmann and Wharton (1958) and by Mitchell and Rhodes (1960). It is probable on the basis of this wide host distribution that this mite parasitizes most, if not all, anatid birds.