Soft ticks, Argasidae, are oval or pear-shaped, with mouth parts that are more easily seen from the ventral view. Ixodes, the hard ticks, possess a dorsal plate or scutum, and many of them can transmit Lyme disease to humans.
North American ticks Argasidae (soft) and Ixodidae (hard)
From Carol & Richard Eustice, About.com
Updated April 30, 2006
About.com Health's Disease and Condition content is reviewed by the Medical Review Board
Soft ticks - Hard Ticks
Photo from Centers for Disease Control and Prevention (CDC)
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