Taxonomy

Morphology

Ixodes ricinus is a tick (order Ixodida) because it has:

  • backwardly-pointing teeth on the hypostome
  • a Haller’s organ on the terminal segment (tarsus) of the front legs -each organ comprises a pit and capsule containing hair-like sensory structures (setae)
  • the external respiratory openings (spiracles) are located on a pair of spiracular plates

 

It is a hard tick (family Ixodidae) because:

  • the gnathosoma (the mouthparts) – comprising the hypostome, palps and chelicerae - is large and clearly visible from above in all life stages
  • the upper body surface is partly (larva, nymph, female) or completely (male) covered by a hardened shield (scutum)

 

The anal groove arching in front of the anus is only seen in the genus Ixodes.

Adult specific character states are:

  • the female scutum is almost circular
  • the basal segment (coxa) of the first pair of legs (legs I) has a long, slender internal spur
  •  all leg coxae have a small external spur
  • the tarsi of legs I taper towards their apex
  • the female genital aperture is between leg coxae IV

 

Look-alikes

Ixodes hexagonus Leach – the hedgehog tick - has a similar distribution to I.ricinus and parasitizes many of the same host species.

 

It can be easily identified by the hump near the apex of tarsus I (absent in I.ricinus), the female genital aperture being between coxae III and not IV, and the rounded hexagonal, rather than circular, scutum.