The mouth-parts of the hard ticks are visible if the tick is inspected from above (in soft ticks the mouth-parts are hidden under the body) (Figure 23.8). The adult male has a hard, dorsal shield (scutum) which covers the whole dorsal part of the body. In the adult female, nymph and larva only the anterior part of the dorsum is covered by the scutum. The ixodids
have only one nymphal stage between the larval and adult stages. While the argasids ingest their blood meals relatively rapidly and may take several blood meal during each active stage (larva, nymphs, adult), the ixodids only ingest one (large) meal during each active stage. In view of their roles as vectors of viroses, rickettsioses, ehrlichioses, tularemia, and babesioses the ixodids are of great medical importance in the tropical, subtropical, and temperate regions. From a veterinary point of view, the Ixodidae is the most important of all arthropod families. Some of the medically most important ixodid species are found in the genera Amblyomma, Dermacentor, Haemaphysalis, Hyalomma, Ixodes, and Rhipicephalus (Sonenshine 1993; Varma 1993).
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