distinct body segmentation characteristic of most arthropods is greatly reduced in the Acari. At the left of the diagram is an anterior section bearing the mouthparts (gnathosoma or capitulum), and at right, a posterior section comprising the main body (idiosoma). Mouthparts are characterized by a central pair of chelicerae, a ventral hypostome, and a lateral pair of palps. Chelicerae are protrusible, cutting or piercing structures essential to feeding. Palps are of sensory function during feeding and do not penetrate the host's skin. Acarines have no antennae and, except for some genera of ticks, are without eyes. A tube for ingesting food and secreting saliva is formed by apposition of both the chelicerae and the hypostome. The main body bears three pairs of legs in the larvae and four pairs in the nymphs and adults. The legs are multiple-jointed and operate by contraction of their internal muscles. The distal segment of the legs, the tarsus, is equipped with a terminal claw or pair of claws and sometimes with an adhesive pad or sucker that enables the mite to crawl up smooth surfaces. The internal organs (or viscera) include a tubular gut with a posterior anus, paired excretory tubes (Malpighian tubules) that empty out into the anus, paired respiratory tubes (tracheae) that carry atmospheric air directly up against the viscera, paired salivary glands with ducts to the mouthparts, female or male reproductive organs (ovary or testes), and a central nervous ganglion that acts as a simple brain. Feeding methods The diagram Mite infestation sites on skin shows where typical infestations of different taxonomic groups mites on livestock animals occur on or in the host's skin. The position of these mites in relation to the skin or other organs is crucial for their feeding and also for their veterinary diagnosis and options for treatment. The mites either feed on the tissues of the skin using penetrating mouthparts or on the inflammatory exudate that results from the action of the mouthparts and saliva of the mites on the skin. Demodectic mites have mouthparts adapted to penetrate and suck out the contents of individual cells of hair follicles. It is usual for all active stages of the mite lifecycle to feed as parasites, but the trombiculid mites are an exception. Most of the parasitic mites do not feed directly on blood, but the dermanyssid mites and larval trombiculid mites directly suck up capillary blood as