The Metastigmata represents the ticks and mites. The Mestastigmata tend to be over 2 mm in length as adults. The respiratory openings, stigmata, are without peritremes and near the base of the fourth pair of legs. This group is divided into three smaller groups, the soft ticks which compose the Argasidae, the hard ticks which compose the Ixodidae, and a poorly known intermediate group, the Nutallidae. Cats are known to be parasitized by both the Argasidae and the Ixodidae. All ticks feed by sucking blood and tissue fluids from a vertebrate host. The Ixodidae are called hard ticks because they bear a cuticularized protective dorsal scutum or shield. This shield is lacking in the Argasidae, and therefore, they tend to be called soft ticks. The soft ticks tend to live in nesting areas, and when the the host is in or on the nest, the soft ticks crawl onto the host and feed rapidly. The hard ticks, on the other hand, tend to await hosts more in the open and to feed more slowly which causes them to be attached to the host for longer periods.