No abstract

The development of Thelazia skrjabini Erschow, 1928, was studied in experimentally infected laboratory-reared Musca autumnalis De Geer. Thelazia skrjabini developed to the infective third stage in a minimum of 9 days in M. autumnalis maintained at 27 +/- 2 C. First-stage larvae were not observed postinoculation, but second-stage larvae were first observed 3 days postinoculation. Development was asynchronous. Second- and third-stage larvae occur in capsules, occasionally in the head but primarily in the abdomen attached to fat bodies. First-stage larvae have anteriorly 1 ventral and 2 dorsal hooks, directed posteriorly. Second-stage larvae have 4 submedian cephalic papillae and faint annular striations. Third-stage larvae have 6 labial papillae, 4 submedian cephalic papillae and pronounced annulations. Morphometric studies of each larval stage were performed with specimens in glycerine.

Acanthocephalus bufonis (Shipley, 1903) Southwell and Macfie, 1925 is redescribed on the basis of specimens collected from the black-spotted toad, Bufo melanostictus Schneider, 1799, from Indonesia. The material collected by Southwell and Macfie in 1925 and by Petrochenko in 1953 is not considered conspecific with that collected by Shipley in 1903. The species described by Petrochenko is given the name Acanthocephalus breviprostatus nom. nov.; that of Southwell and Macfie is unnamed until a more adequate description is produced.

A face fly (Musca autumnalis) population near Wetaskiwin, central Alberta, Canada, was sampled 9 times from 26 July to 29 September 1988 for the early larval stages of Thelazia spp. Of 426 female flies examined, 159 (37%) contained Thelazia spp. (almost exclusively T. skrjabini), with an average worm burden of 4.2 larvae per infected fly. Prevalence ranged from 17 to 56% over 9 collections. This is the first report of Thelazia skrjabini in flies from western North America and the highest Thelazia prevalence in face flies yet reported in North America. The face fly population was also parasitized by Heterotylenchus autumnalis, with a prevalence of 5.5%.

The life cycle of Haematoloechus buttensis was maintained in the laboratory by using the usual natural hosts: Rana pretiosa, Physa nuttalli, and Ischnura perparva. Morphological variations in important taxonomic characters were studied and compared with those found when one of the usual hosts was replaced by a sympatric, but usually uninfected, host. In all, six species of Amphibia, three of Insecta, and three Mollusca were used.The effect of host size, sex, and ambient temperature was also studied using R. pretiosa as definitive host.The most reliable taxonomic characters were determined to be the sucker ratio, egg size of 21-day-old and older worms, position of the testes, and the anterior extent of the extracaecal uterine loops.The unreliability of other characters and their prior use as species-specific features suggests that many of the currently recognized species of Haematoloechus are not valid.