An Old World genus (about 21 species) of large ixodid ticks with submarginal eyes, coalesced festoons, an ornate scutum, and a long rostrum. Adults parasitize all domestic animals and a wide variety of wild animals; larvae or nymphs may parasitize small mammals, birds, and reptiles. Species harbor a great variety of pathogens of humans and animals, and also cause considerable mechanical injury. [hyalo- + G. omma, eye]
