Morphology

Ticks belong to the

• Phylum Arthropoda (Subphylum Chelicerata)
• Class Arachnida (Hey, does this mean they are not insects? Yes, that’s true – ticks are Arthropods, and NOT insects!)
• Order Acarina (Suborder Ixodida)
• Families Argasidae, Ixodidae, and Nutellidae)
  
• Class Arthropoda, Order Acarina
  

A small wingless body defines tick form. Head and thorax are fused into a single segment. Eyes are rare, yet when present are usually small and simple. A capitulum or false head is set apart from the main tick body and consists of the basis capituli, hypostome and chelicerae (teeth). The body walls of argasid ticks (soft ticks) are leathery. The body walls of ixodids (hard ticks) are characterized by a chitinous shield (scutum).

Adult ticks and nymphs possess eight legs. Larvae, called seed ticks, possess six legs; however, the larval ticks are so small that you would have difficulty counting the legs without using a microscope.

Hard Ticks:

In the male hard tick, the scutum covers the entire back region. In the female, the scutum covers only a small portion, allowing for bodily expansion following engorgement.

Hey, does this mean that only the females feed on vertebrate blood? Well, no! Both male and female hard ticks imbibe the blood meal from the host, but male ticks are only intermittent feeders and they do not engorge. The females will not undergo the rapid phase of feeding and engorgement until they have mated with a male tick.

Soft Ticks:

There is no scutum in soft ticks. They feed several times for short periods.