A brown dog tick.
Ticks are a group of more than 800 parasitic arthropods closely related to mites. They feed on the blood of birds, reptiles, and warm-blooded mammals. The life cycle of a tick varies by tick species and family, but generally progresses from an egg to a larva, then a nymph, and finally an adult.
The family Argasidae, or family of soft ticks, includes about 160 species. These arthropods have soft, bulging bodies and hidden mouthparts. Ixodidae, or hard ticks, have rigid, plated bodies and visible mouthparts. Researchers recognized around 650 varieties of hard ticks in 2011.
Ticks found on deer are usually adults.
The life cycle of a tick begins at the egg stage. Both soft and hard ticks hatch into six-legged larvae, also called seed ticks. After molting, they mature into eight-legged nymphs, eventually becoming eight-legged adult ticks that mate, lay eggs, and continue the cycle.
Ticks require a blood meal at every life stage. Larval and nymphal ticks cannot molt and move on to the next stage of their development without ingesting the nutrients provided by the blood. A tick’s life cycle can take up to three years to complete, depending on the number of hosts it requires.
Some hard ticks, such as dog or cattle ticks, feed on a single species and do not change hosts. Others alternate between animals as they mature. Some species have a two-host cycle, but most hard ticks have a three-host cycle.
Depending on sex and type, ticks can expand to different sizes, as large as a grape or as small as an apple seed, when they feed on blood.
A three-host hard tick feeds on the blood of small animals, such as birds or mice, while it is still in the larval stage. After molting and becoming an eight-legged nymph, it transforms into a larger host, such as a rabbit. After molting one last time and becoming an adult tick, it molts a third time, this time into an even larger animal, such as a deer or cow.
A tick’s life cycle also varies by how many times it molts before reaching adulthood. Some types of hard ticks shed only twice. Soft ticks can go through up to seven developmental stages, or instars, before they become adults.
Many ticks fail to complete their life cycle. Some species can survive for months or even years without a blood meal, but a tick’s life cycle ultimately depends on whether the young tick can find a suitable host to feed on and prepare for the next instar. . Most ticks die because they cannot locate a host.