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Developmental Cycle

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Adult

Following the nymphal molt, the ixodid adults emerge to attack hosts, feed, mate, and the fed females drop to oviposit in some sheltered microenvironment, completing the life cycle.

This pattern of host-seeking, feeding and off-the-host molting in each life stage constitute the 3-host life cycle. This is the most common developmental pattern and is characteristic of the vast majority of the species. It is the least highly evolved of the various life cycle patterns. Under favorable conditions in the natural environment, the life cycle of such 3-host ticks, from the time of hatching of the larvae to the hatching of the next generation, can be completed in less than 1 year. However, climatic conditions and diapause may delay host seeking behaviour, development or the onset of oviposition, so that only one life stage can be completed each year. These environmental limitations tend to extend the duration of the life cycle to as much as 3 years (e.g., Ixodes ricinus).

Several variations of this general ixodid developmental pattern exist. In some species, fed larvae remain on the host, molt in situ, and the unfed nymphs reattach. Only following their engorgement do the nymphs detach. Then, they molt off the host to the adult stage. These ticks are known as 2-host ticks.

A more extreme modification occurs in the winter tick Dermacentor albipictus or the cattle tick Boophilus microplus and other Boophilus species. In these species, all stages remain on the host after the larvae attach. These ticks are termed 1-host tick.

In Ixodidae, the emerging adults harden climb to a suitable surface (e.g., tips of vegetation) and commence questing. The cycle is repeated when the ticks contact their host. Host contact is followed by attachment and feeding. Adult ticks may require several days of feeding before they are able to reproduce. Further development is dependent upon mating, which takes place on the host in all metastriate ixodid ticks.

Mated females engorge rapidly to repletion; the fed females detach, and drop off.

Males usually remain to reattach, feed again, and mate with other females. Following a brief period of preovipositional development, they commence oviposition. Alternatively, in some species, replete detached females may enter ovipositional diapause (= development diapause) and remain inactive for several months (e.g., overwinter) before they commence oviposition.

Male hard ticks usually die soon after mating, and females die soon after laying their eggs.

Following emergence, argasid adults may first mate in the niche or attack hosts. Following host contact, adults feed rapidly, engorge and drop off. Mated females oviposit small egg clutches, whereupon they return to attack hosts and feed again. Adults seek hosts, feed and engorge several times and fed mated females oviposit after each blood meal. Adult soft ticks are generally longer-lived, and egg-laying is a periodic activity of the female.

   

Further information

  • Sonenshine DE: Biology of Ticks. Part 1, 1991, Oxford University Press, New York

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