Haemaphysalis (Aboimisalis) vasilisae sp. nov. (Acari: Ixodidae) is described based on males, females, nymphs and larvae that were collected from passerine birds in the United States (Florida, South Carolina and Texas). Adults, nymphs and larvae of this new species are similar to those of H. chordeilis (Packard, 1869) but can be distinguished from them by the color of the conscutum/scutum, dimensions of conscutum/scutum and spiracular plates, shape of the palpal segment II, length of ventral spur on palpal segment III, length of spur on coxae, as well as by other measurements and ratios. The male, female, nymph and larva of H. chordeilis are redescribed based on specimens collected from birds and mammals in Canada (Alberta, Manitoba and Ontario) and the USA (California, Idaho, Massachusetts, Michigan, Minnesota, Montana, Nebraska, New Hampshire, New York, Utah, Vermont, Washington, Wisconsin and Wyoming).
Dmitry A. Apanaskevich (Mon,) studied this question.