Ixodida

Ixodida is an order of arachnids within the class Arachnida and subclass Acari, comprising the ticks. The order contains two families: Ixodidae, the hard ticks, and Argasidae, the soft ticks. There are hundreds of described species, found worldwide in a variety of habitats. Ticks are obligate hematophagous parasites of vertebrates, including mammals, birds, and reptiles, and many species are important vectors of pathogens.

Morphology and life cycle: Hard ticks (Ixodidae) possess a hardened dorsal plate called the scutum; soft ticks (Argasidae) lack a scutum and have a more leathery body. All ticks undergo four life stages: egg, larva (six-legged), nymph, and adult. Most species require a blood meal at each stage, and many reproduce by laying large batches of eggs after engorgement.

Behavior and feeding: Ticks locate hosts by cues such as carbon dioxide and heat; they attach to the skin and insert their mouthparts (capitulum) to feed. Hard ticks feed slowly over days to weeks and often remain attached for the duration, whereas soft ticks tend to feed quickly and repeatedly. Transmission of pathogens occurs mainly during feeding, when the tick is attached.

Pathogens and impact: Ixodid and argasid ticks transmit a range of microorganisms, including bacteria such as Borrelia (Lyme disease), Rickettsia, and Anaplasma, as well as parasites like Babesia. Tick-borne diseases affect humans and domestic animals, with significant public health and economic consequences.

Taxonomy note: Notable genera include Ixodes, Dermacentor, Amblyomma, and Rhipicephalus among hard ticks, and Argas and Ornithodoros among soft ticks.