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HARD AND SOFT TICKS: Distinction

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The following comparisons were derived from Service (2008):

ARGASIDAE (Soft Ticks) Morphology The scutum or "shield" is absent. Mouthparts (capitulum) are not visible in nymphs and adults dorsally, but can be seen in the larvae. Palps appear as legs, and chelicerae have smooth sheaths Coxal organs are present. Life Cycle The eggs are laid in several small batches of 15-100. Nymphs have 4-5 developmental stages. Blood-feeding of adults lasts only about 20-35 minutes on a host, but will resume several times. Ticks will usually feed on about six hosts. Ticks range primarily around a host's dwellings, with not much dispersal. Diseases Spread Ticks are vectors of Relapsing Fever.

IXODIDAE (Hard Ticks) Morphology A scutum is present on larvae, nymphs and adults. It is small in females and large in males. Mouthparts are visible in all developmental stages. Palps are club-shaped, and chelicerae have denticulate sheaths. Coxal organs are absent. Life Cycle One batch of thousands of eggs is laid. Nymphs have only one developmental stage. Blood-feeding on a host is prolonged from one to four weeks. Ticks will usually feed on only two or three hosts. Ticks remain attached to a host for a long time so that they can be spread considerable distances. Diseases Spread Ticks are vectors of Tick Typhus, Lyme Disease and other viruses. They also cause Tick Paralysis.

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Key References: <medvet.ref.htm>

Matheson, R. 1950. Medical Entomology. Comstock Publ. Co, Inc. 610 p.

Service, M. 2008. Medical Entomology For Students. Cambridge Univ. Press. 289 p